WO2017017037A1

WO2017017037A1 - Active noise-control device

Info

Publication number: WO2017017037A1
Application number: PCT/EP2016/067589
Authority: WO
Inventors: Pierre Guiu; Eric Benhaim
Original assignee: Orosound
Priority date: 2015-07-24
Filing date: 2016-07-22
Publication date: 2017-02-02
Also published as: FR3039310A1; EP3326170A1; FR3039310B1; EP3326170B1

Abstract

Disclosed is an active noise-control device comprising two earphones (3) each provided with an external microphone (14), an internal microphone (15) and a loudspeaker (16). The control device comprises a processing chain (30) having a feedforward filter linked to the external microphones, a feedback filter linked to the internal microphones, and a reconstruction module supplying every loudspeaker with a signal reconstructed from the output signals of the feedforward filter and the feedback filter. The processing chain comprises a slicer positioned between the feedforward filter and the reconstruction module to ensure that the volume of the reconstructed sound is not too high. The control device comprises adjustment means for the combined adjustment of the slicer and a total gain of the control device.

Description

The present invention relates to the field of noise reduction and, more particularly, to an active noise control device.

BACKGROUND OF THE INVENTION

Many people work in noisy environments in which they are exposed to very high noise levels from a variety of sources. For example, such noisy environments can be found on construction sites, on demolition sites (blasting), in factories in which mechanical saws are used, and so on. It is necessary, in such noisy environments, to reduce the noise level to protect the hearing of these people.

Others work in noisy environments in which noise levels are consistently lower, which presents a lower risk in the short term of hearing impairment but tends to increase fatigue, stress and decrease attention and concentration skills of these people. Such noisy environments can be found, for example, in shared workspaces ("open space") used in call centers. The noise level must be attenuated to improve the working conditions of these people.

Other people, in a non-professional setting, also want to reduce the noise levels of their environment to improve their comfort when they want to rest, concentrate (for example to read), or when they want to take full advantage of the music they listen to.

In most of these situations, it is important to reduce noise levels effectively, but it can also be very beneficial not to completely acoustically isolate5 the person concerned and to allow him / her to be effectively protected from noise. unwanted, to perceive useful noises: voices, alarms, ringtones, etc. It is very advantageous, in other words, to adapt the level of noise attenuation according to the type of noise and possibly according to the noise level, the type of external environment, etc.

Some hearing protection devices are equipped with noise control systems that can attenuate the noise differently depending on the noise level.

For example, helmets dedicated to the protection of loud noises caused by an impact or an explosion are known. These helmets are mainly used to reduce the sound of gunshots. They limit shooting noises while allowing the user to hear lower level sounds. These headsets include two earphones each generally comprising a shell, a microphone and a speaker. The shell comprises a high density material providing a very important passive attenuation. The microphone picks up the surrounding noise outside the shell and outputs a filtered signal so that sounds that do not exceed a certain predefined threshold (typically 88 dB (A)) are transmitted to a loudspeaker, which then emits them. the user's ear. The voice sounds are for example heard by the user, while the sound of shots are muffled.

Intra-ear earphones are also known operating in a manner similar to the headsets that have just been described and particularly adapted to protecting a user against loud noises such as those encountered during construction work or in particularly noisy industrial environments (see for example, US-A-5,355,418).

These headphones and headphones have at least two disadvantages. The noise control they perform takes into account the noise level but not the type of noise. Of moreover, the predefined thresholds beyond which the noises are not retransmitted are not adjustable according to the conditions of use.

OBJECT OF THE INVENTION

The object of the invention is an inexpensive and easy-to-implement solution making it possible to eliminate at least partially the disadvantages mentioned earlier.

SUMMARY OF THE INVENTION

In order to achieve this goal, an active noise control device is proposed comprising two passive attenuation earpieces each provided with an external microphone, an internal microphone, and a loudspeaker for reproducing a noise. in the atrium. The control device comprises a processing chain comprising a feedforward filter connected to the external microphones, a feedback filter connected to the internal microphones, a reproduction module providing each loudspeaker with a signal reproduced from the output signals of the feedforward filter and the filter feedback. According to the invention, the processing chain comprises a limiting filter positioned between the feedforward filter and the rendering module and arranged to limit the output signals of the feedforward filter so as to avoid that the noise restored has a too high sound level, and the control device comprises adjustment means for adjusting in a combined manner the limiting filter and a total gain of the control device.

The combined setting of the limiter filter and the total gain of the control device makes it possible, depending on the conditions, to adjust the active noise control according to both the type of noise and the noise level. The use of a limiting filter at the output of the feedforward filter to prevent the noise returned has a too high noise level is not very complex and inexpensive to implement, especially in terms of design efforts, integration, test. Other characteristics and advantages of the invention will emerge on reading the following description of a particular, non-limiting embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made to the appended drawings among which:

FIG. 1 represents a user located in a noisy environment and provided with the active noise control device of the invention;

FIG. 2 is a detail view of FIG. 1 showing an atrium of the control device of the invention;

FIG. 3 is an electrical diagram of processing means of the control device of the invention;

FIG. 4 represents a first processing line and a second processing line of the control device of the invention;

FIG. 5 is a diagram of a directional microphone antenna constituted by external microphones of the control device of the invention;

FIG. 6 is a graph showing a passive attenuation curve and a passive and active attenuation curve of the control device of the invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to Figure 1, the active noise control device 1 according to the invention is intended to equip a user 2 located in a noisy environment (working space, etc.).

The control device 1 improves the access of the user 2 to a noise called "useful noise" prevailing in the noisy environment while minimizing as much noise called "unwanted noise" also prevailing in the noisy environment .

As will be seen later in this description here means "useful noise" a particular type of noise having a particular amplitude and from a particular spatial direction.

The control device 1 also allows the user 2 to listen to music. This function will be mentioned very briefly in the remainder of this description because it does not constitute the heart of the invention.

The control device 1 comprises a passive attenuation left atrium 3a and a passive attenuation right atrium 3b each connected by a cable 4 to a housing 5 positioned here in a pocket of a user's jacket 2. Each cable 4 comprises a plurality of conductive wires surrounded by a protective sheath, the conductive wires being intended to transmit various analog and digital electrical signals mentioned below and running between each of the atria 3 and the housing 5.

With reference to FIG. 2, each atrium 3 is here in the form of an in-ear earphone which comprises a body 6 and a tip 7 carried by the body 6.

The tip 7 has a shape adapted to allow the tip 7 to be inserted into an ear canal 8 of an ear 9 of the user 2 by closing said ear canal. The tip 7 holds the atrium 3 in the ear canal 8 of the ear 9 and provides the user 2 passive sound attenuation by producing sound insulation.

Each body 6 delimits an internal acoustic space

11 extending towards the inside of the auditory canal 8 and also defines an external acoustic space 12 extending outside the atrium 3.

Each earpiece 3 furthermore comprises an external microphone 14, an internal microphone 15 and a loudspeaker 16 which equip the body 6 of the atrium 3. The external microphone 14 is mounted on the body 6 outside the internal acoustic space 11 to pick up external noise in the external acoustic space 12 and produce an external electrical signal representative of the external noise. The external electrical signal of each atrium 3 is transmitted to the housing 5 via the cable 4 connecting the atrium 3 to the housing 5.

The internal microphone 15 is mounted in the body 6 to pick up an internal noise prevailing in the internal acoustic space 11 and to produce an internal electrical signal representative of the internal noise. The internal electrical signal of each atrium 3 is transmitted to the housing 5 via the cable 4 connecting the atrium 3 to the housing 5.

The loudspeaker 16 is positioned so as to restore, in the internal acoustic space 11 and thus in the ear canal 8 of the ear 9, a noise reproduced from a restored signal produced by the housing 5 and transmitted by the housing 5 to each atrium 3 via the cable 4 connecting the atrium 3 to the housing 5.

The housing 5, meanwhile, comprises an electrical card on which are mounted a plurality of electronic components constituting processing means 20.

With reference to FIG. 3, the means of treatment

20 comprise a power supply module 21, a microcontroller 22, a clock module 23, an audio source module 24, four analog-to-digital converters 25, two digital-to-analog converters 26, first analog interface components 27, second analog interface components 28 and a DSP 29 (for "Digital Signal Processor").

The power supply module 21 here comprises a rechargeable battery and a power supply circuit which, in particular, manages the charge of the battery and supplies the electrical card and the earphones 3 via the cables 4 one or several supply voltages for powering the electrical components of the card and the ear pieces 3.

The microcontroller 22 and the DSP 29 manage the operation of the electrical card and, more generally, the control device 1 as a whole.

The clock module 23 comprises a clock component (quartz, etc.) used to clock the operations of the microcontroller 22 and thus the operations of the other components (analog-to-digital converters 25, etc.).

The audio source module 24 allows the user to listen to music. The audio source module 24 acquires musical signals which are here transmitted to the box 5 by a telephone via a wireless communication type Bluetooth. The microcontroller 22 in turn receives the musical signals and transmits these musical signals to the earphones 3 via the cables 4 so that the speakers 16 of the earphones 3 restore the music in the internal acoustic space 11 of each atrium 3.

The analog to digital converters 25 convert the external electrical signals and the internal electrical signals produced in the form of analog signals respectively by the external microphones 14 and the internal microphones 15 into digital signals. Similarly, the digital-to-analog converters 26 convert into signals analogous the restored signals and musical signals produced by the microcontroller 22 in the form of digital signals.

The first analog interface components 27 shape (amplify, attenuate, filter, etc.) the external electrical signals and the internal electrical signals produced respectively by the external microphones 14 and the internal microphones 15 in the form of analog signals prior to their conversion into digital signals by the analog-digital converters 25. Likewise, the second analog interface components 28 format (amplification, attenuation, filtering, etc.) the restored signals and the musical signals following their conversion into analog signals by the digital-to-analog converters 26.

The treatments carried out by the control device 1 are now described in more detail.

With reference to FIG. 4, a first processing line 30 is implemented by the microcontroller 22 and the DSP 29 of the processing means 20 of the box 5.

The first processing chain 30 comprises the following function blocks connected in series and successively arranged from upstream to downstream of the first processing line (ie from the input to the output of the first processing line 30): a partition module of the external acoustic space 31, a feedforward module 32, a limitation module 33, a reproduction module 34, an amplification module 35 and a feedback module 36.

The partition module of the external acoustic space 31 has for inputs the external signal produced by the external microphone 14 of the left atrium 3a and the external signal produced by the external microphone 14 of the right atrium 3b. The partition module of the external acoustic space 31 combines the external signal produced by the external microphone 14 of the left atrium 3a and the external signal produced by the external microphone 14 of the right atrium 3b to form a directional microphonic antenna.

The directional microphone antenna has a directivity pattern determined by weighting coefficients and delay coefficients used in the combination of each external signal. The directional microphonic antenna formed here and whose directivity pattern 38 is visible in FIG. 5 is a "1st order bidirectional broadside" antenna.

By varying the direction of the main lobe 39 of the directivity diagram 38 of the microphonic antenna directive, here we define eleven microphone antennas in different directions. The external acoustic space is thus partitioned into eleven incidence sectors Sect_i (visible in FIG. 1 and in FIG. 5, i ranging from 1 to 11) defined in a horizontal plane passing through the external microphones 14. Eleven is then defined Sign_i directional external signals which each correspond to an external directional noise originating from one of the eleven incidence sectors Sect_i.

Each of the eleven directional Sign_i external signals is processed separately by the feedforward module 32 and by the limitation module 33.

The feedforward module 32 comprises eleven feedforward filters FF_i which each filter one of the eleven Sign_i external directional signals. Each feedforward filter FF_i works according to the known principle and not recalled here of the open loop anticipation control.

Thus, the feedforward filter FF_i is adapted either to attenuate or to amplify the external directional noise of the sector of incidence Sect_i and more or less important according to feedforward parameters of the filter FF_i. If the directional external noise is a useful noise, the corresponding directional Sign_i external signal will be amplified by the corresponding feedforward FF_i filter (or retransmitted as is). On the other hand, if the directional external noise is an unwanted noise, the corresponding directional Sign_i external signal will be attenuated by the corresponding feedforward filter FF_i.

Each feedforward FF_i filter typically provides a maximum attenuation of approximately 20dB for directional external frequency noise between 50Hz and 2kHz.

The limiter module 33 comprises eleven limiting filters FL_i which each receive an output signal from one of the eleven feedforward filters FF _^ _i.

Each limiting filter FL_i is arranged to limit the output signal of the feedforward filter FF_i associated to prevent the noise restored in the internal acoustic space 11 and therefore in the auditory canal 8 of each ear 9 of the user 2 has a too high sound level. The limiting filters FL_i thus make it possible to protect the hearing of the user 2 against a loud noise level.

To limit the output signal of the feedforward filter FF_i, the limiting filter FL_i passes the frequency components of the output signal of the feedforward filter FF_i whose amplitude is less than a limitation threshold, and closes at the level of the limitation threshold. amplitude of the frequency components whose amplitude is greater than the limitation threshold.

The rendering module 34 receives the eleven output signals of the limiter module 33 and recombines them taking into account the sector of incidence Sect_i from which they originate in order to respect the partition of the external acoustic space 12. The restitution module 34 also receives the musical signals 40 mentioned earlier.

The reproduction module 34 mixes between the eleven output signals of the recombination limitation module 33 and the musical signals 40 and produces a left-handed signal Sr_g and a right-handed signal Sr _^ _d which respect the binaural perception of the user 2 .

The left-handed signal Srg and the right-handed signal Srd form a stereo signal which is amplified by the amplification module 35 and transmitted to the speaker 16 of the left atrium 3a and to the speaker 16 of the right atrium 3b via the cables 4.

The loudspeaker 16 of the left atrium 3a and the loudspeaker 16 of the right atrium 3b then reproduce a noise respectively restored in the internal acoustic space 11 of the left atrium 3a and in the internal acoustic space 11 of the right atrium 3b of the user 2. Each internal microphone 15 captures the internal noise in the internal acoustic space 11 of the atrium 3 and produces an internal electrical signal representative of the internal noise.

The feedback module 36 has two feedback filters

FB (or "feedback filters"). Each feedback filter FB receives the internal electrical signal from one of the internal microphones 15 and isolates a residual electrical signal corresponding to a residual noise attenuating existing in the internal acoustic space 11. The residual noise is constituted by the combination of the noise that allows the atria 3 to pass into the internal acoustic space 11 and physiological sounds transmitted to the auditory canal by bone conduction.

The feedback filters FB then produce an opposite residual electric signal Ser and transmit the residual electrical signal Ser opposite to the reproduction module 34 so that the reproduction module 34 generates an opposite corrective noise of the same gain and in phase opposition with respect to the residual noise. .

In this way, the residual noise is attenuated, obtaining in particular a maximum attenuation of the order of 30 dB for the low frequency components of the residual noise between 10 Hz and 1 kHz.

The feedback module 36 is thus adapted to attenuate the external noise and this, to a greater or lesser extent as a function of feedback parameters of the feedback filters FB.

As we have just seen, the first processing chain 30 operates using adjustment parameters, which are the feedforward parameters of the feedforward filters FF_i, the feedback parameters of the feedback filters FB and the limiting thresholds of the limiting filters FL_i.

The feedforward parameters, the feedback parameters, the limitation thresholds and the passive attenuation provided by the atria 3 contribute to a total gain of control device 1. The total gain of the control device 1 may be a total amplification or a total attenuation.

The control device 1 comprises first adjustment means implemented in the processing means 20, which make it possible to adjust in a combined manner the limiting thresholds of the limiting filters FL_i, the feedforward parameters of the feedforward filters FF_i and the filter feedback parameters. FB feedback of the first processing chain 30 (and thus the total gain of the control device 1).

The housing 5 of the control device 1 comprises a first user interface 45 (visible in Figure 1) allowing the user 2 of the control device 1 to control the first adjustment means. The first user interface 45 here comprises a potentiometer and one or more adjustment buttons.

The first adjustment means allow the user 2 to select whether the total gain is a total attenuation or a total amplification.

When the user 2 chooses a total attenuation, the user 2 can set a total attenuation level higher or lower than the passive attenuation provided by the earphones 3 themselves.

With reference to FIG. 6, when the total attenuation level is greater than the passive attenuation 46, which corresponds to the dashed hatched area, the first processing chain 30 must produce an additional attenuation to reach the total attenuation level.

This situation occurs in particular when the directional external noise is an unwanted noise that should be significantly reduced.

The feedforward parameters and the feedback parameters are set so that the feedforward filter FF_i concerned and the FB feedback filters bring the complement mitigation.

The first adjustment means comprise means for activating the limiting filters FL_i which, in this situation, deactivate the limiting filter FL_i concerned. The feedforward filter FF_i and the feedback filters FB are then used, via an appropriate setting of feedback parameters and feedforward parameters, to limit the Sign_i directional external signal. This limitation is added to the passive attenuation provided by the earphones 3 and prevents the noise returned has too much noise. The hearing protection of the user 2 is therefore passively provided by the ear pieces 3 and actively by the feedforward filter FF_i and the FB feedback filters when the limiting filter FL_i is deactivated.

When the total gain is a total attenuation lower than the passive attenuation 46, which corresponds to the hatched area in solid lines in FIG. 6, the first processing chain 30 must amplify the noise to reduce the passive attenuation provided by the auricles 3.

Likewise, when the total gain is a full amplification, which corresponds to the hatched area in solid lines in FIG. 6 located below the abscissa axis, the first processing line 30 must amplify the noise to cancel the effect of passive attenuation and provide additional amplification.

These two situations occur in particular when the directional external noise is a useful noise, such as a speech noise, that the user 2 wishes to amplify or at least listen to by reducing the impact of the passive attenuation produced by the atria 3 The directional external Sign_i signal is then retransmitted as is or amplified in a frequency band typically between 50Hz and 8kHz.

The feedforward parameters are set so that the feedforward filters FF_i perform the full amplification. The activation means of the limiting filters FL_i, in these situations, activate the limiting filter FL _^ _i concerned. The protection of the hearing of the user 2 against loud noise level is therefore passively provided by the earphones 3 and actively by the limiting filter FL__i.

It should be noted that, in these two situations, the limitation threshold is set according to the total gain: the greater the amplification provided by the first processing chain, the higher the limitation threshold is. Thus, the loud noise level is limited in proportion to the setting of the total gain made by the user 2. Beyond a certain total gain, the limitation threshold no longer varies, it is then frozen at the maximum level to preserve the ears of the user.

With reference again to FIG. 4, a second processing line 50 is implemented by the microcontroller 22 of the processing means 20 in the housing 5.

The second processing chain 50 comprises a sound source identification module 51.

The identification module 51 has eleven identification entries Ent_i and a parameterization output Sp.

Each identification input Ent_i is connected to the partition module of the external acoustic space 31 and receives one of the eleven external direction signals Sign_i which each correspond to an external directional noise coming from one of the eleven incidence sectors Sect_i .

The parameterization output Sp is connected to the feedforward module 32, to the limitation module 33 and to the feedback module 36.

The identification module 51 is adapted to parameterize the first processing chain 30 via the parameterization output Sp by setting the feedforward module 32 (and thus by setting the feedforward parameters), the module limitation 33 (and thus by setting the limitation thresholds) and the feedback module 36 (and thus by setting feedback parameters).

The control device 1 comprises second adjustment means implemented in the processing means 20 to adjust the identification module 51. The box 5 of the control device 1 comprises a second user interface 53 allowing the user 2 of the control device 1 to control the second adjustment means.

The identification module 51 operates as follows.

With the second user interface 53, the user can select a useful noise type (speech noise, alarm, etc.), first Sectl incidence sectors and second Sect2 incidence sectors from the eleven Sect impact _^ i.

The identification module 51 substantially or totally reduces any directional external noise originating from the second incidence sectors Sect2.

The identification module 51 identifies whether the directional external noise from each first incidence sector Sect1 is a useful noise, depending on the user's choice. The identification of the directional external noise type is performed from a plurality of parameters extracted from the spectral and temporal contents of the directional external signal Sign_i.

If the directional external noise is a useful noise, the identification module 51 sets the first processing chain 30 so that the total gain of the control device 1 is a total amplification, or a total attenuation less than passive attenuation. The total gain level is set via the first adjustment means.

If the external directional noise is an unwanted noise, the identification module 51 sets the first channel in such a way that the total gain of the control device is a strong total attenuation.

It should be noted that the processing carried out by the first processing line 30 and the processing carried out by the second processing line 50 are carried out in parallel, that is to say that the identification module 51 of the second processing line 50 identifies the type or types of noises useful in the first sectors of incidence Sect_l while the first processing chain 30 treats the set of directional external signals Sign_i of the eleven incidence sectors Sect_i.

The parameterization performed by the second processing chain 50 is of course priority over the parameterization achieved via the first adjustment means. If the user 2 selects an incidence sector Sect_i as a second sector Sect2, any directional external noise coming from this sector of incidence is strongly attenuated regardless of the settings produced via the first adjustment means.

The feedforward parameters, the feedback parameters and the limit thresholds of the first processing chain 30 therefore evolve dynamically as a function of the processing performed by the second processing chain 50 (and of course, depending on the settings made by the user 2 via the first adjustment means and the second adjustment means).

The active noise control performed by the first processing line 30 and the second processing line 50 in parallel is thus more reactive but also significantly more efficient. Indeed, the treatments performed by the first processing line 30 are at very low latency, typically about fifty microseconds for the feedforward filters FF_i, while the identification of the noise made by the second processing line 50 requires a time. larger calculation typically between one millisecond and ten milliseconds. The first processing chain 30 therefore does not suffer a delay which would be detrimental both for the processing carried out (for example for the open loop anticipation control performed by each of the feedforward filters), but also for the reproduction of a noise. useful that should not suffer too much delay.

The invention is not limited to the particular embodiment which has just been described, but, on the contrary, covers any variant within the scope of the invention as defined by the claims.

Although an active noise control device comprising two earphones connected by cables to a remote box has been described here, it is perfectly possible to replace the cables with a wireless transmission (Wi-Fi, etc.). integrating the casing processing means in the ear cups (or in only one of the ear cups), integrating the processing means of a plurality of control devices in a remote server communicating via a wireless link with the ear cups, etc. The two atria may also form a helmet with a mechanical link (bow), and may be in the form of intra-auricular headphones but in the form of intra-concha, circumaural, or supralaural devices. etc.

It is further noted that the first processing chain can be perfectly implemented without the second processing chain.

Although it has been indicated that the first processing chain and the second processing chain are implemented "in digital" by the microcontroller and by the DSP, the processing chains can be implemented "in analog", each module or filter then consisting of a plurality of analog components.

Although, in the description, the antenna formed by the two external microphones is a broadside antenna bidirectional order 1, it is perfectly possible to constitute another type of antenna (having a wedge-shaped diagram, hyper-cardioid, etc.). It is also perfectly possible to use a different number of external microphones, and to partition the space into a number of different sectors.

Although the control device allows here to listen to music * this application is in no way restrictive, and the control device can perfectly be intended only to control the noise, or can be connected to a fixed or mobile phone and serve to hold a telephone conversation, etc.

Claims

An active noise control device comprising two passive attenuation earpieces (3) each provided with an external microphone (14), an internal microphone (15), and a speaker (16) for reproducing a noise in the atrium; the control device comprising a processing chain (30) comprising a feedforward filter (FF_i) connected to the external microphones, a feedback filter (FB) connected to the internal microphones, a reproduction module (34) providing each loudspeaker with a signal outputted from the output signals of the feedforward filter and the feedback filter; the control device being characterized in that the processing chain comprises a limiting filter (FL_i) positioned between the feedforward filter and the rendering module and arranged to limit the output signals of the feedforward filter so as to avoid that the noise restored has an excessive sound level, the limiting filter (FL_i) passing frequency components of the output signal of the feedforward filter whose amplitude is less than a limitation threshold, and clipping at the level of the limiting threshold the amplitude of the frequency components of which the amplitude is greater than the limiting threshold, and in that the control device comprises adjustment means for adjusting in a combined manner the limitation threshold of the limiting filter and a total gain of the control device.

2. Control device according to the claim

1, wherein the adjustment means are arranged to select whether the total gain is total attenuation or total amplification and to set a total attenuation or amplification level.

3. Control device according to one of the preceding claims comprising means activation of the limiting filter (FL_i).

4. Control device according to claims 2 and 3, wherein the activation means are arranged to activate the limiting filter when the total gain is a total amplification or a total attenuation less than the passive attenuation produced by the atria ( 3), and wherein the activation means are arranged to deactivate the limiting filter in the opposite case.

5. Control device according to the claim

4, wherein, when the limiting filter is off, the feedforward filter (FF_i) and / or the feedback filter (FB) are arranged to provide additional attenuation so that the total attenuation is equal to the sum of the passive attenuation and mitigation complement.

6. Control device according to one of the preceding claims further comprising a user interface (45) allowing a user of the control device to control the adjustment means.

7. Control device according to one of the preceding claims, wherein the processing chain comprises a partition module of an external acoustic space (31), the partition module (31) being located upstream of the feedforward filter and using a directional microphone antenna formed by the external microphones.