EP0549836A1 - Multi-dimensional sound reproduction system - Google Patents
Multi-dimensional sound reproduction system Download PDFInfo
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- EP0549836A1 EP0549836A1 EP91312109A EP91312109A EP0549836A1 EP 0549836 A1 EP0549836 A1 EP 0549836A1 EP 91312109 A EP91312109 A EP 91312109A EP 91312109 A EP91312109 A EP 91312109A EP 0549836 A1 EP0549836 A1 EP 0549836A1
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- localized
- listener
- speaker
- speakers
- head
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04S—STEREOPHONIC SYSTEMS
- H04S1/00—Two-channel systems
- H04S1/002—Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution
- H04S1/005—For headphones
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2420/00—Details of connection covered by H04R, not provided for in its groups
- H04R2420/07—Applications of wireless loudspeakers or wireless microphones
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04S—STEREOPHONIC SYSTEMS
- H04S5/00—Pseudo-stereo systems, e.g. in which additional channel signals are derived from monophonic signals by means of phase shifting, time delay or reverberation
Definitions
- the present invention pertains in general to a sound reproduction system, and more particularly, to a sound reproduction system for a multi-dimensional space using a binaural recording.
- the sound can either appear as an echo to an individual, or as just a mere coloration of the direct sound. If the delay between two identical sounds is separated in time by around 10 mS, the sound will be perceived as a coloration of the direct sound, whereas for delays greater than around 50 mS, the sound will be perceived as an echo. Therefore, if the delayed sound were directed toward the listener from a rearward position with a delay between 10-50 mS relative to the direct sound, the listener would not perceive the location of the rearmost sound source, but, rather, he would experience a fuller and perhaps more intelligible sound at his location. Essentially, the human ear tends to lock on sound which arrives first.
- multi-dimensional sound typically referred to as 3-D sound
- multi-dimensional sound has been reproduced through either headphones or through loudspeakers.
- loudspeakers it is important that the listener not move, since very complex systems have been developed which provide for cancellation of cross-talk between loudspeakers.
- the rooms in which these experiments have been carried out typically are acoustically "dead" rooms.
- Q-biphonic system One system that has been provided to reproduce binaural signals though loudspeakers is the Q-biphonic system.
- This system utilizes a binaural synthesizer that takes pre-recorded monaural sources and converts them into binaural signals along with loudspeaker cross-talk cancellation circuitry necessary for playback through loudspeakers.
- These systems claim to achieve full azimuthal localization in a four speaker system in addition to elevation localization.
- This system is very sensitive to head movement and is restricted to only one listening position. In the early days of this system, it was found that an anechoic space was needed.
- Another solution proposed for a multi-dimensional system is one utilizing a multiple delay line system controlled by a personal computer. Provisions are made for six delay lines and an additional four non-delay lines.
- sounds can be localized by controlling the signal arrival times between loudspeakers in a multiple speaker system.
- adjustable delay there is also an adjustable attenuation provided for each line. The individual delay times and attenuation calculations, which are accomplished on a computer, achieve the desired effect, i.e., phantom imaging. Delay times can be updated to account for moving sources through the use of the mouse, and preset configurations can be stored for future reference.
- a recording system that employs an artificial head for making the recordings. This is sometimes referred to as a "dummy" head.
- the system utilizes an artificial head that is fabricated from an anthropromorphic mannequin-like device that has lifelike pinnas and microphones disposed in the ear canals.
- the microphones are disposed on either side of the artificial head, and these microphones are utilized in conjunction with a binaural processor that converts the standard signals into binaural signals.
- the artificial head is typically utilized as an area microphone with additional circuitry provided for replicating the recordings of soloists which are converted and blended with the area recording.
- the head is equalized for a flat free-field response at frontal incidence.
- the experience of listening to binaural recordings through headphones typically produces interior or "in-the-head” sounds. This is due to the disturbance of the conch resonance in the pinna by earphone cups, which causes a sense of nearness and "in the head” localization.
- the free-field equalization removes this resonance during recording, while for playback, the headphones are equalized to restore this resonance. It can be appreciated that the headphones destroy the natural conch resonance.
- the equalization of the response with the headphones results in better external localization, which is still because of the uniqueness of the transfer function of the pinna of each individual.
- the artificial head recordings made with the free-field equalization will reproduce with good results through regular stereo equipment. Furthermore, if these binaural recordings are reproduced through loudspeakers utilizing cross-talk cancelization (transaural listening), the conch resonance of the pinna is not presented twice, but is only restored by the natural action of the outer ear.
- the present invention disclosed and claimed herein comprises a multi-dimensional sound reproduction system for reproducing binaural recordings having first and second channels.
- the system includes first and second localized speakers for receiving and reproducing the first and second channels, respectively, of the binaural recording.
- a support member is provided for disposing the first and second localized speakers in a substantially fixed position on opposite sides of the head.
- the first and second localized speakers are supported such that they are proximate to the left and right ears, respectively, of the listener in such a position that each of the first and second localized speakers does not disturb the natural frequency response of the ears of the listener. They are sufficiently close to the head such that cross-talk between each of the first and second localized speakers and the ear on the opposite side of the head of the listener is minimized.
- circuitry for extracting a portion of the frequency spectrum from each of the first and second channels of the binaural recording. At least one of these extracted portions of the frequency spectrum of the first and second channels of the binaural recording is output to an external speaker that is disposed away from the listener.
- this comprises a lowpass filter/crossover circuit wherein the low frequency portion of each of the first and second channels of the binaural recording are extracted, summed and then output to the external speaker.
- a highpass filter/crossover circuit is utilized to remove the low frequency portion of the frequency spectrum from the signals input to the first and second localized speakers.
- the first and second localized speakers are supported in an eyeglass frame.
- the eyeglass frame is supported on the listener's head with a headband.
- Speaker housings are disposed on the headband to secure the localized speakers.
- the localized speakers are positioned such that they are directed rearward toward the pinna of the associated left and right ear and disposed proximate to the zygomatic arch of the listener.
- FIGURE 1a there is illustrated a schematic diagram of a prior art system for recording and playing back binaural sound.
- the prior art system is divided into a recording end and a playback end.
- a dummy head 10 In the recording end, a dummy head 10 is provided which has microphones 12 and 14 disposed in place of the ear canals.
- Two artificial pinnas 16 and 18, respectively, are provided for approximating the response of the human ear.
- the output of each of the microphones 12 and 14 is fed through pre-filters 20 and 22, respectively, to a plane 24, representing the barrier between the recording end and the playback end.
- the transfer function between the artificial ears 16 and 18 and the barrier 24 represents the first half of an equalizing system with the pre-filters 20 and 22 providing part of this equalization.
- the playback end includes a listener 26 which has headphones comprised of a left earpiece 28 and a right earpiece 30.
- a correction filter 32 is provided between the barrier 24 and the earphone 28 and a correction filter 34 is provided between the barrier 24 and the earphone 30.
- the correction filter 34 is connected to the output of the pre-filter 20 and the correction filter 32 is connected to the output of the pre-filter 22.
- the transfer function between the barrier 24 and the earphone 30 represents the playback end transfer function.
- the product of the recording end transfer function and the playback end transfer function represents the overall transfer function of the system.
- the pre-filters 20 and 22 and the correction filters 32 and 34 provide an equalization which, when taken in conjunction with the response of the dummy head, should result in a true reproduction of the sound. It should be appreciated that the earphones 28 and 30 alter the natural response of the pinna for the listener 26, and therefore, the equalization process must account for this.
- FIGURE 1b there is illustrated a diagrammatical representation of a prior art system, which is similar to the system of FIGURE 1a with the exception that speakers 38 and 40 replace the headphones 28 and 30 and associated correction filters 32 and 34.
- speakers 38 and 40 replace the headphones 28 and 30 and associated correction filters 32 and 34.
- one problem that exists is cross-talk between the two speakers, since the speakers are typically disposed a large distance from the ears of the listener. Therefore, sound emanating from speaker 40 can impinge upon both ears of the listener 26, as can sound emitted by speaker 38. Further, the room acoustics would also affect the sound reproduction in that reflections occur from the walls of the room.
- Headphones as compared to speakers, are usually equalized to a free field in that their transfer function ideally corresponds to that of a typical external ear when sound is presented in a free sound field directly from the front and from a considerable distance. This does not lend itself to reproduction from a loudspeaker.
- loudspeakers will require some type of equalization to be performed at the recording end, but this will still result in distortions of tone and color. It can be seen that although the loudspeakers can be somewhat equalized with respect to a given position, the cross-talk of the speakers must be accounted for. However, when dealing with a large auditorium, this must occur for all the listeners at any given position, which is difficult at best.
- FIGURE 2 there is illustrated a diagram of the system of the present invention.
- the binaural recording is input to a signal conditioner 44 as a left and a right signal on lines 46 and 48, respectively.
- the signal conditioner 44 as will be described hereinbelow, is operable to combine the left and the right signals for frequencies below 250 Hz and input them to low frequency speaker 52, there being no left or right distinctions made in the speaker 52.
- the left and right signals of lines 46 and 48 are output as separate signals on left and right lines 54 and 56 to localized speakers 58 and 60 which are disposed proximate to the ears of the listener 26.
- the localized speakers 58 and 60 are disposed such that they do not disturb the natural conch resonance of the ears of the listener 26, and they are disposed such that the sound emitted from either of the speakers 58 and 60 is significantly attenuated with respect to the hearing on the opposite side of the head. This is facilitated by disposing the localized speakers 58 and 60 proximate to the head such that the natural separation provided by the head will be maintained.
- FIGURE 3 there is illustrated a diagram of the system utilized with a plurality of listeners 26.
- Each of the listeners 26 has associated therewith a set of localized speakers 58 and 60.
- the listeners 26 are disposed in a room 64 with the speaker 52 disposed in a predetermined and fixed location. Since it is desirable that sound from the speaker 52 arrive at all of the listeners 26 generally at the same time, the speaker 52 would be located some distance from the listeners 26, it being understood that Figure 3 is not drawn to scale.
- a viewing screen 65 is disposed in front of the listeners 26 to provide visual cues.
- the localized speakers 58 and 60 are supported on the heads of listeners 26 such that they are maintained at a predetermined and substantially fixed position relative to the head. Therefore, if the head were to move when, for example, viewing a movie, there would be no phase change in the sound arriving at either of the ears of the listener 26. Therefore, a support member is provided which is affixed to the head of the listener 26 to support the localized speakers 58 and 60.
- groups consisting of six listeners are connected to common wires 54 and 56, such that the localized speakers 58 and 60 associated with each of the listeners 26 in a common group are connected to these wires, respectively.
- the sound level is adjusted such that each listener 26 will hear the sound at the appropriate phase from the associated one of the localized speakers 58 and 60.
- a listener 26 disposed in an adjacent seat with sound being emitted from his associated localized speakers 58 and 60 will not interfere with the sound received by the one listener 26. This is due to the fact that the sound levels are relatively low. If the localized speakers 58 and 60 are removed, then a listener 26 can hear sound emitted from localized speakers 58 and 60 among the listeners' seats adjacent thereto. The human ear "locks" onto the sound emitted from its associated localized speakers 58 and 60 and tends to ignore the sound from speakers disposed adjacent thereto. This is the result of many factors, including the Law of the First Wavefront described hereinbelow.
- the combination of the localized speakers 58 and 60 and visual cues on the screen 65 provide an additional aspect to the listener's ability to localize sound. In general, the listener cannot localize sound very well when it is directly in front or in back of the listener's head. Some type of head movement or visual cue would normally facilitate localization of the sound. Since the localized speakers 58 and 60 are fixed to the listener's head, visual cues on the screen 65 provide the listeners 26 with additional information to assist in localizing the sound.
- the localized speaker 58 is disposed proximate to the right ear of the listener and its associated pinna 66.
- the localized speaker 60 is disposed proximate to the left ear of the listener 26 and the associated pinna 68.
- the localized speakers 58 and 60 are disposed forward of the pinnas 66 and 68, respectively, and proximate to the head of the listener 26. It has been determined experimentally that the optimum sound reproduction occurs when the speaker is directed rearward and disposed proximate to the zygomatic arch of the listener 26. If the associated localized speaker 58 or 60 is moved outward, directly to the side of the ear, the actual physical size of the speaker tends to disturb the conch resonance. However, if the speaker were reduced to an extremely small size, this would be acceptable.
- the speaker It is important that the speaker not be moved too far from the listener, as cross-talk would occur. Of course, any type of separation in the front, the rear or on top of the head would improve this.
- the torso provides separation beneath the head, but it would be necessary to improve the separation in the space forward, rearward and upward of the head if the localized speakers 58 and 60 were moved away from the head.
- the localized speakers 58 and 60 are designed to be utilized in an auditorium with multiple users all receiving the same or similar signals. Therefore, they are disposed as close to the ear as possible without disturbing the conch resonance and to minimize the sound level necessary for output from the localized speakers 58 and 60.
- FIGURE 5 there is illustrated a perspective view of the support mechanism for the localized speakers 58 and 60.
- the localized speakers 58 and 60 are supported in a pair of three-dimensional glasses 70, which are designed for three-dimensional viewing. These glasses 70 typically have LCD lenses 72 and 74 which operate as shutters to provide the three-dimensional effect.
- a control circuit is disposed in a housing 76 which has a photo transistor 78 disposed on the frontal face thereof. The photo transistor 78 is part of a communications system that allows the synchronization signals to be transmitted to the glasses 70.
- Housing 80 is disposed on one side of the glasses 70 for supporting the localized speaker 58.
- a housing 82 is disposed on the opposite side of the glasses 70 for supporting the localized speaker 60.
- the housings 80 and 82 provide the proper acoustic termination for the speakers 58 and 60, such that the frequency response thereof is optimized.
- the speakers 58 and 60 are typically fabricated from a dynamic loudspeaker, which is conventionally available for use in stereo headphones.
- FIGURE 6 there is illustrated a side view of the housing 82 and the localized speaker 60.
- the localized speaker 60 as described above, is disposed such that it is proximate to the side of the head in the area of the zygomatic arch. It is directed rearward toward the pinna 68 of the left ear of the listener 26 with the sound emitted therefrom being picked up by the pinna 68 and the ear canal of the left ear of the listener 26.
- FIGURE 7 there is illustrated a detailed view of the housing 82 and the speaker 60.
- the housing 82 is slightly widened at the mounting point for the localized speaker 60, which, as described above, is a small dynamic loudspeaker.
- a wire 84 is provided which is disposed through the housing 82 up to the control circuitry in the housing 76. Alternatively, the wire 84 can go to a separate control/driving circuit that is external to the housing 82 and the glasses 70.
- the housing 82 is fabricated such that it has a cavity disposed therein at the rear of the localized speaker 60. The size of this cavity is experimentally determined and is a function of the particular brand of dynamic loudspeaker utilized for the localized speakers 58 and 60. This cavity is determined by measuring the response of the particular dynamic loudspeaker with a variable cavity disposed on the rear side thereof. This cavity is varied until an acceptable response is achieved.
- FIGURE 8 there is illustrated a schematic block diagram of the system for driving the localized speakers 58 and 60 and also the low frequency speaker 52.
- the binaural recording system typically provides an output from a tape recording, which is played back and output from a binaural source 90 to provide left and right signals on lines 92 and 94. These are input to a 4x4 circuit 96 that outputs left and right signals on lines 98 and 100 for localized speakers 58 and 60, and also a summed signal on a line 102, which comprises the sum of both the left and right signals.
- the 4x4 circuit 96 is manufactured by OXMOOR CORPORATION as a Buffer Amplifier and is operable to receive up to four inputs and provide up to four outputs as any combination of the four inputs or as the buffered form of the inputs.
- the signal line 102 is output to a crossover circuit 112 which is essentially a low pass filter. This rejects all signals above approximately 250 Hz.
- the crossover circuit 112 is typical of Part No. AC 22, which is a stereo two-way crossover, manufactured by RANE CORPORATION.
- the output of the crossover 112 is input to a digital control amplifier (DCA) 108 to control the signal level. This is controlled by volume level control 110.
- the DCA 108 is typical of Part No.
- the output of the DCA 108 is input to an amplifier 114 which drives the speaker 52 with the low frequency signals.
- the amplifier 114 is typical of Part No. 800X, manufactured by SONICS ASSOCIATES, INCORPORATED.
- the left and right signals on lines 98 and 100 from the 4x4 circuit 96 are input to a delay circuit 106, which is typical of Part No. DN775, which is a Stereo Mastering Digital Delay Line, manufactured by KLARK-TEKNIK ELECTRONICS INC.
- the outputs of the delay circuit 106 are input to a high pass filter 118 to reject all frequencies lower than 250 Hz.
- the high pass filter 118 is identical to the part utilized for the crossover circuit 112.
- the outputs of filter 118 are input to a headphone mixer 120 to provide separate signals on a multiplicity of lines 122, each set of lines comprising a left and a right line for an associated set of localized speakers 58 and 60 for listeners 26. This is typical of Part No. HC-6, which is a headphone console, manufactured by RANE CORPORATION.
- the lines 122 are routed to particular listeners' localized speakers 58 and 60.
- FIGURE 9 there is illustrated a detailed schematic diagram of the circuit for driving the headphones.
- Line 98 is input through delay 106, and high pass filter 118 to the wiper of a volume control 124, the output of which is input to the positive input of an operational amplifier (op amp) 126.
- the output of op amp 126 is connected to a node 128 which is also connected to the base of both an NPN transistor 130 and a PNP transistor 132.
- Transistors 130 and 132 are configured in a push-pull configuration with the emitters thereof tied together and to an output terminal 134.
- the collector of transistor 130 is connected to a positive supply and the collector of transistor 132 is connected to a negative supply.
- the emitters of transistors 130 and 132 are also connected through a resistor 136 to the node 128.
- the negative input of the op amp 126 is connected through a resistor 138 to ground and also through a feedback resistor 140 to the output terminal 134.
- An op amp 142 is provided with the positive input thereof connected to the output of volume control 125.
- the wiper of volume control 125 is connected through delay 106 and the filter 118.
- Op amp 142 is configured similar to op amp 126 with an associated NPN transistor 144 and PNP transistor 146, configured similar to transistors 130 and 132.
- a feedback resistor 148 is provided, similar to the resistor 140, with feedback resistor 148 connected to the negative input of op amp 142 and an output terminal 150.
- a resistor 152 is connected to the negative input of op amp 142 and ground.
- the volume controls 124 and 125 provide individual volume control by the listener 26.
- Line 98 is also illustrated as connected through a summing resistor 156 to a summing node 158.
- the line 100 is connected through a summing resistor 160 to the summing node 158.
- the summing node 158 is connected to the negative input of an op amp 162, the positive input of which is connected to ground through a resistor 164.
- the negative input of op amp 162 is connected to the output thereof through a feedback resistor 166.
- Op amp 162 is configured for unity gain at the first stage.
- the output of op amp 162 is connected through a resistor 170 to a negative input of an op amp 172.
- the negative input of op amp 172 is also connected to the output thereof through a resistor 174.
- op amp 172 The positive input of op amp 172 is connected to ground through a resistor 176.
- Op amp 172 is configured as a unity gain inverting amplifier.
- the output of op amp 172 is connected to an output terminal 178 to provide the sum of the left and right channels.
- the op amps 162 and 172 provide the function of the summing portion of 4x4 circuit 96, and are provided by way of illustration only.
- FIGURE 10 there is illustrated a block diagram of an alternate method for transmitting the left and right signals to the localized speakers 58 and 60.
- the binaural source has electronic signals modulated onto a carrier by a modulator 180, the carrier then transmitted by transmitter 182 over a data link 184.
- the data link 184 is comprised of an infrared data link that has an infrared transmitting diode 185 disposed on the transmitter 182.
- a receiver 186 is provided with a receiver Light Emitting Diode 188 that receives the transmitted carrier from the diode 185.
- the output of the receiver 186 is demodulated by a demodulator 190 and this provides a left and right signal for input to the conditioning circuit 44.
- a multi-dimensional sound reproduction system comprising of two localized speakers which are supported in a substantially fixed relationship with respect to the head of a listener.
- the localized speakers are disposed proximate to the ear in such a position that they do not disturb the natural response of the ear, and sufficiently close to the head such that the cross-talk between each of the speakers and the opposite ear is minimized.
- Low frequency sound that does not contain important localization cues is filtered from the original binaural recording, and this is transmitted to the listener by an external speaker.
Abstract
Description
- The present invention pertains in general to a sound reproduction system, and more particularly, to a sound reproduction system for a multi-dimensional space using a binaural recording.
- In stereophonic sound systems, such as those found in home entertainment applications, there is an attempt to control the localization of sounds typically using balance potentiometers. In this process, the relative level between two loudspeakers affects where the phantom image will exist as perceived by a listener positioned equidistant from two loudspeakers with respect to a single plane. The perception of where the sound originates, i.e., the phantom image, has also been observed to be a function of the delay between the two otherwise identical sources. For gradual increasing delays, which are on the order of the Interaural Time Difference (ITD) between the ears, the phantom image will shift toward the real undelayed source, which is disposed away from the phantom image. As the amount of delay is increased toward 10 mS, sound direction is "fused" to the speaker from which the sound first arrived. In fact, it has been observed that if two similar sounds, which originate from separate sources are delayed with repsect to each other by an amount that is between 10 mS - 50 mS, a listener who is positioned equidistant from the two loudspeakers will perceive the sound to be coming from the direction of the speaker whose sound arrives first, to the exclusion of the second speaker. This has been referred to as the Law of the First Wavefront, the Precedence Effect or the Haas Effect.
- For sound arriving from two different sources, be they reflections or delayed sources, the sound can either appear as an echo to an individual, or as just a mere coloration of the direct sound. If the delay between two identical sounds is separated in time by around 10 mS, the sound will be perceived as a coloration of the direct sound, whereas for delays greater than around 50 mS, the sound will be perceived as an echo. Therefore, if the delayed sound were directed toward the listener from a rearward position with a delay between 10-50 mS relative to the direct sound, the listener would not perceive the location of the rearmost sound source, but, rather, he would experience a fuller and perhaps more intelligible sound at his location. Essentially, the human ear tends to lock on sound which arrives first.
- The above observations can generally be explained based on the theory that the position of a sound source is cued by interaural differences in the intensity and time of arrival (phase). This is the so-called duplex theory of localization which states that phase is the main mechanism of the localization below 1500 Hz, while for frequencies above around 4000 Hz, intensity is the main localization cue. For the intervening range of frequencies, localization is not good and it may be that confusion comes about because of conflict between the two mechanisms over this range of frequencies. The duplex theory of localization will break down when it comes to defining unique sound source positions. A sound source which is located directly in front of a listener and one which is located directly behind a listener provides identical signals to the ears according to the duplex theory. However, it is a common everyday experience to discriminate between front and back localized sounds. There is much evidence to support the idea that a third mechanism contributes to the localization of sound, and that is the pinna transformation of sound.
- Over the years, experiments have shown that the pinna performs a spectral modification which gives additional cues for the localization of sounds. This is particularly true with respect to elevation and front-back cues. The brain/nervous systems appears to process angular dependant spectral information in order to determine direction. This is due to the complex shape of the pinna which, when presented to a sound in front of the user, results in a significantly different response to the ear canal as compared to that for a sound originating from behind the listener. This spectral modification is also affected by the head and torso.
- For multi-dimensional sound, typically referred to as 3-D sound, it is necessary to localize the sound, identify moving sound sources, enlarge the ideal listening area for the listener and remove the actual sound from a viewing area, such as a movie screen, to the individual. When considering only a single individual in a room, multi-dimensional sound has been reproduced through either headphones or through loudspeakers. With respect to the loudspeakers, it is important that the listener not move, since very complex systems have been developed which provide for cancellation of cross-talk between loudspeakers. Further, the rooms in which these experiments have been carried out typically are acoustically "dead" rooms.
- One system that has been provided to reproduce binaural signals though loudspeakers is the Q-biphonic system. This system utilizes a binaural synthesizer that takes pre-recorded monaural sources and converts them into binaural signals along with loudspeaker cross-talk cancellation circuitry necessary for playback through loudspeakers. These systems claim to achieve full azimuthal localization in a four speaker system in addition to elevation localization. This system is very sensitive to head movement and is restricted to only one listening position. In the early days of this system, it was found that an anechoic space was needed.
- Another solution proposed for a multi-dimensional system is one utilizing a multiple delay line system controlled by a personal computer. Provisions are made for six delay lines and an additional four non-delay lines. By utilizing a computer "mouse", which provides coordinate manipulation, sounds can be localized by controlling the signal arrival times between loudspeakers in a multiple speaker system. In addition to the adjustable delay, there is also an adjustable attenuation provided for each line. The individual delay times and attenuation calculations, which are accomplished on a computer, achieve the desired effect, i.e., phantom imaging. Delay times can be updated to account for moving sources through the use of the mouse, and preset configurations can be stored for future reference.
- Some present research that is going on in the multi-dimensional sound system field is that for developing a multisensory "virtual environment" work station (VIEW) for use in space station teleoperation, tele-presence and automation activities. The auditory requirements for this project led to the prototyping of a binaural signal processor for converting generated or recorded sounds into binaural signals. Researchers measured a subject's pinna responses as a function of azimuth and elevation and arrived at pure head related transfer functions (HRTFs) using Fast Fourier Transform techniques. These HRTFs were implemented in a Digital Signal Processing (DSP) device which allowed the user to apply direction dependent equalization to an incoming signal. By establishing the proper relationship between the ITD, the Interaural Level Difference (ILD), and the HRTF, experimenters were able to synthesize free field stimuli and present this over headphones. Motion trajectories and static locations that represented greater resolution of HRTFs than measured were arrived at through interpolation. However, this system had some problems with front-back reversals.
- To record binaural soundtracks, a recording system has been utilized that employs an artificial head for making the recordings. This is sometimes referred to as a "dummy" head. The system utilizes an artificial head that is fabricated from an anthropromorphic mannequin-like device that has lifelike pinnas and microphones disposed in the ear canals. The microphones are disposed on either side of the artificial head, and these microphones are utilized in conjunction with a binaural processor that converts the standard signals into binaural signals. The artificial head is typically utilized as an area microphone with additional circuitry provided for replicating the recordings of soloists which are converted and blended with the area recording.
- In the recording process utilizing the artificial head, the head is equalized for a flat free-field response at frontal incidence. This accomplishes two things. First, the experience of listening to binaural recordings through headphones typically produces interior or "in-the-head" sounds. This is due to the disturbance of the conch resonance in the pinna by earphone cups, which causes a sense of nearness and "in the head" localization. The free-field equalization removes this resonance during recording, while for playback, the headphones are equalized to restore this resonance. It can be appreciated that the headphones destroy the natural conch resonance. The equalization of the response with the headphones results in better external localization, which is still because of the uniqueness of the transfer function of the pinna of each individual.
- Secondly, the artificial head recordings made with the free-field equalization will reproduce with good results through regular stereo equipment. Furthermore, if these binaural recordings are reproduced through loudspeakers utilizing cross-talk cancelization (transaural listening), the conch resonance of the pinna is not presented twice, but is only restored by the natural action of the outer ear.
- In U.S. Patent No. 4,817,149, issued March 28, 1989, a system is disclosed that enables sounds to be localized from all directions when played through headphones. Elevation and front/back cues are established utilizing direction-dependant filtering while horizontal (aximuthal) localization is achieved by control of interaural time differences.
- The present invention disclosed and claimed herein comprises a multi-dimensional sound reproduction system for reproducing binaural recordings having first and second channels. The system includes first and second localized speakers for receiving and reproducing the first and second channels, respectively, of the binaural recording. A support member is provided for disposing the first and second localized speakers in a substantially fixed position on opposite sides of the head. The first and second localized speakers are supported such that they are proximate to the left and right ears, respectively, of the listener in such a position that each of the first and second localized speakers does not disturb the natural frequency response of the ears of the listener. They are sufficiently close to the head such that cross-talk between each of the first and second localized speakers and the ear on the opposite side of the head of the listener is minimized.
- In another embodiment of the present invention, circuitry is provided for extracting a portion of the frequency spectrum from each of the first and second channels of the binaural recording. At least one of these extracted portions of the frequency spectrum of the first and second channels of the binaural recording is output to an external speaker that is disposed away from the listener. In one aspect of the present invention, this comprises a lowpass filter/crossover circuit wherein the low frequency portion of each of the first and second channels of the binaural recording are extracted, summed and then output to the external speaker. Further, a highpass filter/crossover circuit is utilized to remove the low frequency portion of the frequency spectrum from the signals input to the first and second localized speakers.
- In a further embodiment of the present invention, the first and second localized speakers are supported in an eyeglass frame. The eyeglass frame is supported on the listener's head with a headband. Speaker housings are disposed on the headband to secure the localized speakers. The localized speakers are positioned such that they are directed rearward toward the pinna of the associated left and right ear and disposed proximate to the zygomatic arch of the listener.
- The invention (and for comparison purposes the prior art) will be described, by way of example only, reference being made to the accompanying drawings, in which:-
- FIGURES 1a and 1b illustrate diagrams of the prior art multi-dimensional sound systems;
- FIGURE 2 illustrates a block diagram of the present invention;
- FIGURE 3 illustrates a diagram of the present invention utilized with a plurality of listeners in an auditorium;
- FIGURE 4 illustrates a detail of the orientation of the localized speakers;
- FIGURE 5 illustrates a perspective view of the support mechanism for these speakers;
- FIGURE 6 illustrates a side view of the housing and the localized speaker;
- FIGURE 7 illustrates a detail rear perspective view of the housing for containing one of the localized speakers;
- FIGURE 8 illustrates a schematic block diagram of the system for generating the localized speaker driving signals;
- FIGURE 9 illustrates a schematic diagram for generating the signals for driving the localized speakers; and
- FIGURE 10 illustrates a block diagram of an alternate method for transmitting the binaural signals to the listener over a wireless link.
- Referring now to FIGURE 1a, there is illustrated a schematic diagram of a prior art system for recording and playing back binaural sound. The prior art system is divided into a recording end and a playback end. In the recording end, a
dummy head 10 is provided which hasmicrophones artificial pinnas microphones pre-filters plane 24, representing the barrier between the recording end and the playback end. The transfer function between theartificial ears barrier 24 represents the first half of an equalizing system with the pre-filters 20 and 22 providing part of this equalization. - The playback end includes a
listener 26 which has headphones comprised of aleft earpiece 28 and aright earpiece 30. Acorrection filter 32 is provided between thebarrier 24 and theearphone 28 and acorrection filter 34 is provided between thebarrier 24 and theearphone 30. Thecorrection filter 34 is connected to the output of the pre-filter 20 and thecorrection filter 32 is connected to the output of the pre-filter 22. The transfer function between thebarrier 24 and theearphone 30 represents the playback end transfer function. The product of the recording end transfer function and the playback end transfer function represents the overall transfer function of the system. The pre-filters 20 and 22 and the correction filters 32 and 34 provide an equalization which, when taken in conjunction with the response of the dummy head, should result in a true reproduction of the sound. It should be appreciated that theearphones listener 26, and therefore, the equalization process must account for this. - Referring now to FIGURE 1b, there is illustrated a diagrammatical representation of a prior art system, which is similar to the system of FIGURE 1a with the exception that
speakers headphones speaker 40 can impinge upon both ears of thelistener 26, as can sound emitted byspeaker 38. Further, the room acoustics would also affect the sound reproduction in that reflections occur from the walls of the room. - Headphones, as compared to speakers, are usually equalized to a free field in that their transfer function ideally corresponds to that of a typical external ear when sound is presented in a free sound field directly from the front and from a considerable distance. This does not lend itself to reproduction from a loudspeaker. In general, loudspeakers will require some type of equalization to be performed at the recording end, but this will still result in distortions of tone and color. It can be seen that although the loudspeakers can be somewhat equalized with respect to a given position, the cross-talk of the speakers must be accounted for. However, when dealing with a large auditorium, this must occur for all the listeners at any given position, which is difficult at best.
- Referring now to FIGURE 2, there is illustrated a diagram of the system of the present invention. The binaural recording is input to a
signal conditioner 44 as a left and a right signal onlines signal conditioner 44, as will be described hereinbelow, is operable to combine the left and the right signals for frequencies below 250 Hz and input them tolow frequency speaker 52, there being no left or right distinctions made in thespeaker 52. In addition, the left and right signals oflines right lines localized speakers listener 26. Thelocalized speakers listener 26, and they are disposed such that the sound emitted from either of thespeakers localized speakers - Only signals above 250 Hz are transmitted to the localized
speakers localized speakers speaker 52, such that the sound emitted fromspeaker 52 will arrive at the location of thelistener 26 at the approximate time that the sound is emitted fromlocalized speakers listener 26 from thespeaker 52. It has been noted that the important localization cues are not contained in the low frequency portion of the signal. Therefore, this low frequency portion of the audio spectrum is split out and routed to the listeners through thespeaker 52. In this manner, the amount of sound energy that can be output at the low frequencies is increased, since the small size of the transducers that will be utilized for thelocalized speakers - Referring now to FIGURE 3, there is illustrated a diagram of the system utilized with a plurality of
listeners 26. Each of thelisteners 26 has associated therewith a set oflocalized speakers listeners 26 are disposed in aroom 64 with thespeaker 52 disposed in a predetermined and fixed location. Since it is desirable that sound from thespeaker 52 arrive at all of thelisteners 26 generally at the same time, thespeaker 52 would be located some distance from thelisteners 26, it being understood that Figure 3 is not drawn to scale. Aviewing screen 65 is disposed in front of thelisteners 26 to provide visual cues. - The
localized speakers listeners 26 such that they are maintained at a predetermined and substantially fixed position relative to the head. Therefore, if the head were to move when, for example, viewing a movie, there would be no phase change in the sound arriving at either of the ears of thelistener 26. Therefore, a support member is provided which is affixed to the head of thelistener 26 to support the localizedspeakers common wires localized speakers listeners 26 in a common group are connected to these wires, respectively. The sound level is adjusted such that eachlistener 26 will hear the sound at the appropriate phase from the associated one of the localizedspeakers listener 26 disposed in an adjacent seat with sound being emitted from his associatedlocalized speakers listener 26. This is due to the fact that the sound levels are relatively low. If thelocalized speakers listener 26 can hear sound emitted fromlocalized speakers localized speakers - The combination of the localized
speakers screen 65 provide an additional aspect to the listener's ability to localize sound. In general, the listener cannot localize sound very well when it is directly in front or in back of the listener's head. Some type of head movement or visual cue would normally facilitate localization of the sound. Since the localizedspeakers screen 65 provide thelisteners 26 with additional information to assist in localizing the sound. - Referring now to FIGURE 4, there is illustrated a detail of the orientation of the localized
speakers listener 26. The localizedspeaker 58 is disposed proximate to the right ear of the listener and its associatedpinna 66. Similarly, the localizedspeaker 60 is disposed proximate to the left ear of thelistener 26 and the associatedpinna 68. In the preferred embodiment, thelocalized speakers pinnas listener 26. It has been determined experimentally that the optimum sound reproduction occurs when the speaker is directed rearward and disposed proximate to the zygomatic arch of thelistener 26. If the associated localizedspeaker - It is important that the speaker not be moved too far from the listener, as cross-talk would occur. Of course, any type of separation in the front, the rear or on top of the head would improve this. The torso, of course, provides separation beneath the head, but it would be necessary to improve the separation in the space forward, rearward and upward of the head if the
localized speakers localized speakers speakers - Referring now to FIGURE 5, there is illustrated a perspective view of the support mechanism for the
localized speakers localized speakers dimensional glasses 70, which are designed for three-dimensional viewing. Theseglasses 70 typically haveLCD lenses housing 76 which has aphoto transistor 78 disposed on the frontal face thereof. Thephoto transistor 78 is part of a communications system that allows the synchronization signals to be transmitted to theglasses 70. -
Housing 80 is disposed on one side of theglasses 70 for supporting the localizedspeaker 58. Ahousing 82 is disposed on the opposite side of theglasses 70 for supporting the localizedspeaker 60. Thehousings speakers speakers - Referring now to FIGURE 6, there is illustrated a side view of the
housing 82 and the localizedspeaker 60. The localizedspeaker 60, as described above, is disposed such that it is proximate to the side of the head in the area of the zygomatic arch. It is directed rearward toward thepinna 68 of the left ear of thelistener 26 with the sound emitted therefrom being picked up by thepinna 68 and the ear canal of the left ear of thelistener 26. - Referring now to FIGURE 7, there is illustrated a detailed view of the
housing 82 and thespeaker 60. Thehousing 82 is slightly widened at the mounting point for the localizedspeaker 60, which, as described above, is a small dynamic loudspeaker. Awire 84 is provided which is disposed through thehousing 82 up to the control circuitry in thehousing 76. Alternatively, thewire 84 can go to a separate control/driving circuit that is external to thehousing 82 and theglasses 70. Thehousing 82 is fabricated such that it has a cavity disposed therein at the rear of the localizedspeaker 60. The size of this cavity is experimentally determined and is a function of the particular brand of dynamic loudspeaker utilized for thelocalized speakers - Referring now to FIGURE 8, there is illustrated a schematic block diagram of the system for driving the
localized speakers low frequency speaker 52. The binaural recording system typically provides an output from a tape recording, which is played back and output from abinaural source 90 to provide left and right signals onlines 4x4 circuit 96 that outputs left and right signals onlines localized speakers line 102, which comprises the sum of both the left and right signals. The4x4 circuit 96 is manufactured by OXMOOR CORPORATION as a Buffer Amplifier and is operable to receive up to four inputs and provide up to four outputs as any combination of the four inputs or as the buffered form of the inputs. Thesignal line 102 is output to acrossover circuit 112 which is essentially a low pass filter. This rejects all signals above approximately 250 Hz. Thecrossover circuit 112 is typical of Part No.AC 22, which is a stereo two-way crossover, manufactured by RANE CORPORATION. The output of thecrossover 112 is input to a digital control amplifier (DCA) 108 to control the signal level. This is controlled byvolume level control 110. TheDCA 108 is typical of Part No. DCA-2, manufactured by OXMOOR CORPORATION. The output of theDCA 108 is input to anamplifier 114 which drives thespeaker 52 with the low frequency signals. Theamplifier 114 is typical of Part No. 800X, manufactured by SONICS ASSOCIATES, INCORPORATED. - The left and right signals on
lines 4x4 circuit 96 are input to adelay circuit 106, which is typical of Part No. DN775, which is a Stereo Mastering Digital Delay Line, manufactured by KLARK-TEKNIK ELECTRONICS INC. The outputs of thedelay circuit 106 are input to ahigh pass filter 118 to reject all frequencies lower than 250 Hz. Thehigh pass filter 118 is identical to the part utilized for thecrossover circuit 112. The outputs offilter 118 are input to aheadphone mixer 120 to provide separate signals on a multiplicity oflines 122, each set of lines comprising a left and a right line for an associated set oflocalized speakers listeners 26. This is typical of Part No. HC-6, which is a headphone console, manufactured by RANE CORPORATION. Thelines 122 are routed to particular listeners'localized speakers - Referring now to FIGURE 9, there is illustrated a detailed schematic diagram of the circuit for driving the headphones.
Line 98 is input throughdelay 106, andhigh pass filter 118 to the wiper of avolume control 124, the output of which is input to the positive input of an operational amplifier (op amp) 126. The output ofop amp 126 is connected to anode 128 which is also connected to the base of both anNPN transistor 130 and aPNP transistor 132.Transistors output terminal 134. The collector oftransistor 130 is connected to a positive supply and the collector oftransistor 132 is connected to a negative supply. The emitters oftransistors resistor 136 to thenode 128. The negative input of theop amp 126 is connected through aresistor 138 to ground and also through afeedback resistor 140 to theoutput terminal 134. - An
op amp 142 is provided with the positive input thereof connected to the output ofvolume control 125. The wiper ofvolume control 125 is connected throughdelay 106 and thefilter 118.Op amp 142 is configured similar toop amp 126 with an associated NPN transistor 144 andPNP transistor 146, configured similar totransistors feedback resistor 148 is provided, similar to theresistor 140, withfeedback resistor 148 connected to the negative input ofop amp 142 and anoutput terminal 150. Aresistor 152 is connected to the negative input ofop amp 142 and ground. The volume controls 124 and 125 provide individual volume control by thelistener 26. -
Line 98 is also illustrated as connected through a summingresistor 156 to a summingnode 158. Similarly, theline 100 is connected through a summingresistor 160 to the summingnode 158. The summingnode 158 is connected to the negative input of anop amp 162, the positive input of which is connected to ground through aresistor 164. The negative input ofop amp 162 is connected to the output thereof through afeedback resistor 166.Op amp 162 is configured for unity gain at the first stage. The output ofop amp 162 is connected through aresistor 170 to a negative input of anop amp 172. The negative input ofop amp 172 is also connected to the output thereof through aresistor 174. The positive input ofop amp 172 is connected to ground through aresistor 176.Op amp 172 is configured as a unity gain inverting amplifier. The output ofop amp 172 is connected to anoutput terminal 178 to provide the sum of the left and right channels. Theop amps 4x4 circuit 96, and are provided by way of illustration only. - Referring now to FIGURE 10, there is illustrated a block diagram of an alternate method for transmitting the left and right signals to the localized
speakers modulator 180, the carrier then transmitted bytransmitter 182 over adata link 184. The data link 184 is comprised of an infrared data link that has aninfrared transmitting diode 185 disposed on thetransmitter 182. Areceiver 186 is provided with a receiverLight Emitting Diode 188 that receives the transmitted carrier from thediode 185. The output of thereceiver 186 is demodulated by ademodulator 190 and this provides a left and right signal for input to theconditioning circuit 44. - In summary, there has been provided a multi-dimensional sound reproduction system. The system is comprised of two localized speakers which are supported in a substantially fixed relationship with respect to the head of a listener. The localized speakers are disposed proximate to the ear in such a position that they do not disturb the natural response of the ear, and sufficiently close to the head such that the cross-talk between each of the speakers and the opposite ear is minimized. Low frequency sound that does not contain important localization cues is filtered from the original binaural recording, and this is transmitted to the listener by an external speaker.
- Although the preferred embodiment has been described in detail, it should be understood that various changes, substitutions and alterations can be made therein without departing from the spirit and scope of the invention.
Claims (23)
- A multi-dimensional sound reproduction system for reproducing audio signals having at least a first channel, comprising:
at least a first localized speaker; and
a support for supporting said at least first localized speaker in a substantially fixed position on one side of the head and proximate to the ear, respectively, of the listener in such a position that said at least first localized speaker does not disturb the natural frequency response of the ear of the listener, said localized speaker disposed sufficiently close to the head such that cross-talk between the at least first localized speaker and the ear on the opposite side of the head of the listener is minimized. - A multi-dimensional sound reproduction system for reproducing audio signals having first and second channels, comprising:
a first localized speaker;
a second localized speaker; and
a support for supporting said first and second localized speakers in a substantially fixed position on opposite sides of the head and proximate to the left and right ears, respectively, of the listener in such a position that each of said first and second localized speakers does not disturb the natural response of the ears of the listener, said localized speakers disposed sufficiently close to the head such that cross-talk between each of said first and second localized speakers and the ear on the opposite side of the head of the listener is minimized. - The sound reproduction system of Claim 2 and further comprising:
at least one external speaker;
a filter circuit for extracting a predetermined portion of the frequency spectrum of at least one of the first and second channels of the audio signals; and
a mixing circuit for outputting the extracted portion of the frequency spectrum from the at least one of the first and second channels of the audio signals to drive said speaker. - The sound reproduction system of Claim 3 wherein said filter circuit is operable to extract the predetermined portion of the frequency spectrum from both of the first and second channels of the audio signal, and said mixer is operable to combine the extracted portion of the frequency spectrum of the first and second channels of the audio signal into a monaural signal for output on said external speaker.
- The reproduction system of Claim 3 wherein the portion of the frequency spectrum of the first and second channels of the audio signal extracted by said filter circuit comprise the low frequency end of the frequency spectrum of the first and second channels of the audio signal.
- The sound reproduction system of Claim 2 wherein said first and second localized speakers are disposed proximate to the zygomatic arch of the listener and directed rearward toward the pinna of the left and right ears of the listener.
- The sound reproduction system of Claim 2 wherein said support comprises:
a support member for being supported on the head of the listener;
first and second speaker housings secured to said support member, each of said first and second speaker housings supporting said first and second localized speakers, respectively, in a position wherein said first and second localized speakers are disposed proximate to and away from the associated one of the left and right ears of the listener. - The sound reproduction system of Claim 7 wherein said first and second speaker housings secure and orient said associated first and second localized speakers, respectively, such that they are directed rearward toward the associated one of pinnas of the associated one of the left and right ears of the listener and slightly forward thereof.
- The sound reproduction system of Claim 8 wherein said first and second localized speakers are supported by said associated first and second speaker housings, respectively, such that they are disposed proximate to the zygomatic arch of the listener on the associated side of the listener's head.
- The sound reproduction system of Claim 7 wherein each of said first and second speaker housings includes a cavity for being disposed about the rear of said associated first and second localized speakers to provide the proper acoustic termination for said associated first and second localized speakers.
- The sound reproduction system of Claim 2 and further comprising a display device for outputting visual cues to the listener which, in conjunction with the audio signals, enhances the listener's ability to localize sound reproduced by said first and second localized speakers.
- The sound reproduction system of Claim 2 and further comprising:
an audio signal source for generating the first and second channels of the audio signals on first and second outputs; and
a communication link for connecting the first and second outputs of said audio signal source to said first and second localized speakers. - The sound reproduction system of Claim 12 wherein said communication link comprises a wireless communication link.
- The sound reproduction system of Claim 2 wherein the audio signals comprise binaural recordings.
- A method for reproducing audio signals having first and second channels, comprising the steps of:
disposing a first localized speaker proximate to one of the left and right ears of a listener in such a position that the first speaker does not disturb the natural frequency response of the ears of the listener, the first speaker being sufficiently close to the head, such that cross-talk between the first localized speaker and the ear of the listener on the opposite side of the head is minimized;
disposing a second localized speaker on the opposite side of the head from the first localized speaker and proximate to the other of the left and right ears of the listener in such a position that the second localized speaker does not disturb the natural frequency response of the ears of the listener, the second localized speaker being sufficiently close to the head such that cross-talk between the second localized speaker and the ear on the opposite side of the head is minimized;
inputting the first channel of the audio signal to the first localized speaker;
inputting the second channel of the audio signal to the second localized speaker; and
supporting the first and second speakers in their respective position such that they are substantially fixed relative to the head of the listener. - The method of Claim 15 and further comprising:
extracting a predetermined portion of the frequency spectrum from at least one of the first and second channels of the audio signal;
providing an external speaker; and
outputting the extracted portion of the frequency spectrum of the first or second channel of the audio signal to the speaker. - The method of Claim 16 wherein the step of extracting is operable to extract the predetermined portion of the frequency spectrum from both the first and second channels of the audio signal.
- The method of Claim 16 wherein the extracted portion comprises the lower end of the frequency spectrum that extends from a predetermined frequency point downward in frequency.
- The method of Claim 15 wherein the first and second localized speakers are disposed proximate to the zygomatic arch of the listener.
- The method of Claim 15 and further comprising outputting visual cues to the listener which, in conjunction with the audio signal, enhance the listener's ability to integrate the visual and auditory cues.
- The method of Claim 15 and further comprising:
generating the audio signals on the first and second channels; and
transmitting the audio signals over a communication link to the first and second localized speakers. - The method of Claim 21 wherein the communication link is a wireless communication link.
- The method of Claim 15 wherein the audio signals are a binaural recordings.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP19910312109 EP0549836B1 (en) | 1991-12-31 | 1991-12-31 | Multi-dimensional sound reproduction system |
ES91312109T ES2093083T3 (en) | 1991-12-31 | 1991-12-31 | MULTIDIMENSIONAL SOUND REPRODUCTION SYSTEM. |
DE1991620823 DE69120823T2 (en) | 1991-12-31 | 1991-12-31 | Multidimensional sound reproduction system |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP19910312109 EP0549836B1 (en) | 1991-12-31 | 1991-12-31 | Multi-dimensional sound reproduction system |
Publications (2)
Publication Number | Publication Date |
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EP0549836A1 true EP0549836A1 (en) | 1993-07-07 |
EP0549836B1 EP0549836B1 (en) | 1996-07-10 |
Family
ID=8208526
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP19910312109 Expired - Lifetime EP0549836B1 (en) | 1991-12-31 | 1991-12-31 | Multi-dimensional sound reproduction system |
Country Status (3)
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EP (1) | EP0549836B1 (en) |
DE (1) | DE69120823T2 (en) |
ES (1) | ES2093083T3 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5459790A (en) * | 1994-03-08 | 1995-10-17 | Sonics Associates, Ltd. | Personal sound system with virtually positioned lateral speakers |
US5661812A (en) * | 1994-03-08 | 1997-08-26 | Sonics Associates, Inc. | Head mounted surround sound system |
US5841879A (en) * | 1996-11-21 | 1998-11-24 | Sonics Associates, Inc. | Virtually positioned head mounted surround sound system |
US6144747A (en) * | 1997-04-02 | 2000-11-07 | Sonics Associates, Inc. | Head mounted surround sound system |
WO2004091257A1 (en) * | 2003-04-11 | 2004-10-21 | Koninklijke Philips Electronics N.V. | System comprising sound reproduction means and ear microphones |
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1991
- 1991-12-31 ES ES91312109T patent/ES2093083T3/en not_active Expired - Lifetime
- 1991-12-31 DE DE1991620823 patent/DE69120823T2/en not_active Expired - Fee Related
- 1991-12-31 EP EP19910312109 patent/EP0549836B1/en not_active Expired - Lifetime
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FR2006116A1 (en) * | 1968-03-19 | 1969-12-19 | Matsushita Electric Ind Co Ltd | |
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EP0284286A2 (en) * | 1987-03-25 | 1988-09-28 | Bose Corporation | Stereo electroacoustical transducing |
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5459790A (en) * | 1994-03-08 | 1995-10-17 | Sonics Associates, Ltd. | Personal sound system with virtually positioned lateral speakers |
US5661812A (en) * | 1994-03-08 | 1997-08-26 | Sonics Associates, Inc. | Head mounted surround sound system |
US5841879A (en) * | 1996-11-21 | 1998-11-24 | Sonics Associates, Inc. | Virtually positioned head mounted surround sound system |
US6144747A (en) * | 1997-04-02 | 2000-11-07 | Sonics Associates, Inc. | Head mounted surround sound system |
WO2004091257A1 (en) * | 2003-04-11 | 2004-10-21 | Koninklijke Philips Electronics N.V. | System comprising sound reproduction means and ear microphones |
Also Published As
Publication number | Publication date |
---|---|
EP0549836B1 (en) | 1996-07-10 |
DE69120823D1 (en) | 1996-08-14 |
ES2093083T3 (en) | 1996-12-16 |
DE69120823T2 (en) | 1997-03-13 |
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