US3193609A - Volume control for electronic organs - Google Patents

Description

ATTORNEY July 6, 1965 A. MEYER VOLUME CONTROL FOR ELECTRONIC OHGANS 3 Sheets-Sheet 1 Filed Aug. 29, 1961 ONU .Smm j n v .Gauw .wuotauwzmm w20? am. .iowa

A. MEYER VOLUME CONTROL FOR ELECTRONIC ORGANS July e, 1965 3 Sheets-Sheet 2 Filed Aug. 29. 1961 July e, 1965 A. MEYE 3,193,609

VOLUME CONTROL FOR ELECTRONIC ORGANS Filed Aug. 29, 1961 3 Sheets-Sheet I5 INVENTOR '17 ALBERT MEYr-:z f5 f6 ATTORNEYS United States Patent O 3,193,609 VOLUME CONTROL FOR ELECTRNIC ORGANS Albert Meyer, Deer Park, Ohio, assigner to D. H. Baldwin Company, a corporation of Ohio Filed Aug. 29, 1961, Ser. No. 134,629 19 Claims. (Cl. Sti-1.27)

The present invention relates generally to electronic musical systems and more particularly to systems for controlling volume and tone of an electronic musical instrument, such as an electronic organ, in such manner as to simulate certain characteristics of a pipe organ.

In the course of development of electronic organs, various expedients have been developed and utilized to enable electronic simulation of pipe organs. For example, the various tone colors, chorus and celeste effects of pipe organs have been well duplicated electronically,

In pipe organs, as the swell shutters are closed, the higher frequencies are attenuated more than the lower frequencies, as a function of shutter position. If, then, a network were designed for an electronic organ, which, in response to actuation of the expression pedal to reduce output of the electronic organ, controlled the tone of the instrument by attenuating the higher frequencies more than the lower frequencies, in accordance with a suitable attenuation versus frequency characteristic, a further point of similarity between pipe andfelectronic organs would have been established.

Attainment of the specified attenuation versus frequency characteristic may be accomplished remotely, according to a feature of the present invention, in response to a gain control voltage. In such case the further feature and advantage may be achieved that the time delay inherent ,in operation of the swell shutters of a pipe organ may be electronically simulated.V This may be accomplished by inserting a suitable time constant circuit in the gain control voltage channel. Thereby, very simple single-ended circuitry in the gain controlled stage can be free of D.C. transients in the signal output.

It is, accordingly, a broad object of the present invention to provide an electronic organ system having novel tonal effects simulating the tonal effects provided by a pipe organ on manipulation of the swell shutters.

It is another object of the invention to provide a system for controlling attenuation as a function of frequency, in a broad band signal channel, as a function of gain of the channel.

A further object of the invention resides in the provision of a novel control circuit for an audio channel, wherein a substantially linear attenuation is achieved as a function of frequency, the slope of the attenuation characteristic being a function of gain of the channel.

It is still another object of the present invention to provide a novel remotely controlled volume control circuit for an electronic organ.

The above and still further objects, features and advantages of the present invention will become vapparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a block diagram of a simple form of electronic organ,`including a volume control network;

FIGURE 2 is a circuit diagram of one form of volume control network according to the present invention;

FIGURE 3 is a plot of frequency response characteristics of the circuit of FIGURE' 2;

FIGURE 4 is a vcircuit diagram Vof a further form of volume control network according to the present invention;

FIGURE 5 is a plot of frequency response of the network of FIGURE 4;

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FIGURE 6 is a block diagram of an alternate form of the circuit of FIGURE 2 or 4;

FIGURE 7 is a block diagram of a modification of the system of FIGURE 6;

FIGURE 8 is a schematic circuit diagram correspond ing with FIGURE 7;

FIGURE 9 is a schematic circuit diagram of a modification of the circuit of FIGURE 8; n

FIGURE l0 is a schematic circuit diagram of a further rnodification of the system of FIGURES 8 and 9, and

FIGURE 1l is a drawing showing the means of achieving a constant slope response.

Referring now more particularly to FIGURE 1 of the accompanying drawings, there is illustrated in schematic fashion a typical source of an audio band representing music, and specifically a simple electronic organ, including tone generators 11, and operating key switches 12 in cascade therewith, in a manner which is per se conventional.

Separate arrays of key switches 12a, 12b, 12C are provided for pedal, great and swell tones, in a relatively cornplex organ, in accordance with usual and standard'practice. The keyed outputs deriving from key switchesA 12a, 12b and 12e, are passed through tone color lilters'13a, 13b, and 13C, respectively, which are selected by suitable switches (not shown). The outputs of the selected filters 13a, 13b, 13C may be additively combined inl a mixer amplifier 14, and the combined signal amplified in a power amplifier 1S and radiated acoustically by means of a loudspeaker 16, or some equivalent form of acoustic radiator. Organs as currently sold commercially may include only a single manual or array of key switches, or in complex organs more than one may be employed. Moreover, the audi-o output may include more than a single loudspeaker, and/ or more than one channeLeach channel with separate expression, and horns or tone chambers may be employed to supplement these. y

For most forms of electronic organs the gain of the amplifier channel is controlled by means of a gain control unit responsive to a pedal 17, which is termed in the art an expression pedal.

In an example of the present invention, as applied to a simple organ, there is inserted in the amplifier channel prior to the power amplifier 15 a volume control network, 18, in which attenuation is introduced by actuation of the expression pedal, such that the slope of the response characteristic, i.e. attenuation as a function of frequency, increases, in response to actuation of the expression pedal 17 to reduce volume. The required characteristic is such as to simulate the tonal characteristics of a pipe organ as the swell shutters are closed. With the shutters full open, attenuation in db per decade may be taken to be zero. As the shutters are closed the slope magnitude may increase approximately linearly to approximately 7 to l0 db per decade for full closure, the attenuation for very low frequencies remaining virtually unaiiected, and the attenuation for higher frequencies increasing.

The required characteristics can be achieved electrically by means of `an RC L network having multiple shunt circuits which include resistance and capacitance in series (one shunt branch may be pure resistance), the

several shunt circuits being quite different in time con- -stants, and being selected in accordance with principles well understood in the art of circuit synthesis. It has been determined that three shunt circuits provide a close approximation t-o a system which provides a linear atten-uation vs. frequency characteristic for all attenuation settings. A closer approximation can be attainedV by using more than three shunt circ-nits, while even Itwo such circuits might be adequate. FIGURE 11 shows the means susanna of achieving a substantially uniform slope between zero and -20 db per decade, by using segments of zero slope alternating with segments of -20 'db .per decade slope, where the extents of the segments have been controlled to yield not only the desired overall slope but also the uniformity of this slope. For the characteristic shown in FIGURE ll, the slope magnitude is given by the equation provided the following condition for constant slope is satisfied.

The transfer function for the network yresponse given in etc.

FIGURE 12 is where the variable is complex frequency, s: -t-jw. De-

-sign frequencies f1 through f1,- were used to obtain, by circuit synthesis means, the networks shown in the drawsisting of Variable resistance R, circuit values being speci- ,fled on the drawings.

An output terminal for the network is indicated by reference numeral 23, and an input terminal by reference numeral 24.

When the network is driven by a voltage source of Zero impedance at input -terminal 24, if R is reduced to zero, transmission is at at no loss. At intermedia-te values of resistance R, the response curves are substantially linear, but have a slope depending on the value of R. At the indicated maximum value of R an approximate slope of minus 7 'db per decade is achieved. Plots of [frequency responses versus values of R for the circuit of FIGURE 2 are provided in FIGURE 3 of the accom- .panying drawings.

Referirng to FIGURE 4 of the accompanying drawings, a variant of the system of FIGURE 2 is illustrated, including a fixed series resistance RA, and three shunt paths 30, 31, 32, each comprising, respectively, one of resistances R1, R2, R3, :and one of capacitances C1, C2, C3, all taken to ground in series with a variable resistance R. For very large, or infinite, values of R the shunt paths become inoperative, and the network provides a flat characteristic. The shunt paths are rendered more and more ettective as the value of R is reduced, until, for zero value of R (with other component values as shown) a maximum slope of about minus lO d'o per decade is achieved.

lFIGURE 5 is a set of graphs of attenuation vs. frequency for various values of R, in the circuit of FIG- URE 4, Awhen the shunt paths employ the circuit values sho-wn in the drawings.

The .systems of FIGURES 2 and 4 are satisfactory where the values of R may be varied at will by mechanical means, and may be utilized as the volume control network 18 in the organ of FIGURE 1. However, tor many purposes, in electronic organ systems, electrical control of attenuation is desirable, to enable remote control of audio channels. Remote control of attenuation as a func- Ition of frequency may be accomplished by means of the network schematically represented in FIGURES 6 and 7 of the accompanying drawings.

In essence, a tranfers function may be employed which Cil il has two components. Suitable transfer functions might be:

(l) A(S)=K1l-Af(s) (2) A(S)=K2-'A2(S) where the Ks are const-ants. The desired minimum volume response characteristic necessitates the use of Equation 2, wherein K2 represents a flat frequency-response for full volume transmission. A2 represents a response characteristic which must be subtracted from K2 to obtain the desired shut-ter closed transmission characteristic. To obtain values intermediate the fully closed and fully open conditions, the value of A2 is reduced in response to a D.C. control voltage, to have Values intermediate A2=0 and A2=maximum- F or A2=O, full volume is obtained and when A2=maxi mum, minimum volume is obtained.

Two generic types of circuitry may be employed, to `derive the transfer function of Equation 2, which are exemplied in FIGURES 6 and 7. In FIGURES 6, 50 is a signal. input terminal. Divided paths lead from signal input terminal 5d, directly to a subtractive network 51, and via a ltcr network 52, to subtractive network 51. The filter network 52 includes a series impedance, consisting of capacitor 53, two shunt paths 54, 55, consisting of resistances R1, R2, respectively, and capacitances C1, C2, respectively, in series, and terminating xed resistance R2 in series with a voltage divider R1 which is controlled by the expression pedal.

In FIGURE 7, the input terminal is i60. Terminal 60 is connected directly to an adding stage 61, and also via an attenuation control channel 63, including a iilter network, 64, in cascade with a phase reversing gain control device 6S, responsive to a D.C. gain control voltage supplied over lead 66.

The filter network, 64, may duplicate the network 52 of FIGURE 6, excepting that a tixed resistance would be used in place of the potentiometer.

In the system of FIGURE 6 the `lilter network 52 supplies a variable fraction of its output to subtractive network 51, the response of the ilter network SZbeing A2 in Equation 2. In the sys-tem of FIGURE 7 a similar result, i.e. subtraction of the attenuated effect A2, from the direct effect R2, is obtained by reversing the phase of A2 and adding, i.e. adding K2 and (-A2). The value of A2 may be varied between Zero and a maximum value by varying the gain of amplifier in the circuitry of FIGURE 7, `or by varying voltage division through R4 in the -circuitry of FIGURE 6.

In the systems of FIGURES 6 and 7, then, a filter network is employed which has appropriate frequency response, but variable amounts of the output o'this network are subtracted from a flat response network, to achieve a desired total response A which is adjustable to have any slope between 0 and 7 to 10 db per decade.

In some electronic organ installations, the generators, tone color circuits and speakers or other acoustic radiators are located remotely of the organ console, and the power amplifiers are located adjacent to the speakers. The expression pedal is by necessity part of the console. It is, therefore, desirable to provide a remotely controllable volume control, which may include Lswell shutter eitect, i.e. simulation of the attenuation characteristics of pipe organ swell shutters.

A schematic circuit diagram corresponding with the block diagram of FIGURE 7 is provided in FIGURE 8. In FIGURE 8, is an input terminal. Between terminal '70 and ground is provided a voltage divider 71 having a variable tap 62. The latter is connected to a iilter network having a series capacitor C and two shunt paths comprising resistances R1, R2, respectively, in series with capacitors C1, C2, respectively. The input terminal 70 is connected through a xed resistance 73 to an output terminal ground. The junction 76 of capacitor C and resistors R1, R2 is coupled via a coupling capacitor 77 to the suppressor grid 78 of a pentode 79. Y

Pentode 79 includes an anode 80, a screen grid 81, a control grid 82 and a grounded cathode 83. An anode load 84 is connected between B+ terminal and anode 80. Screen grid 81 is connected to a source of fixed positive potential 85. Control grid 82 is connected to a source of variable D.C. control voltage, 87, while anode 80 is A.C. coupled via capacitor 88 and resistance 89 to output terminal 74. Control voltage source 87 in an organ installation, includes a potentiometer which is actuated by an expression pedal.

Ther audio spectrum applied to input terminal 70 is transferred, without attenuation as a function of frequency, to output terminal 74. The same audio spectrum is attenuated in filter network'90, the circuit values (specified in the drawings) providing an appropriate frequency response,

but an outputamplitude which is a function of the posi- `tion of variable tap 62, which is a Calibrating adjustment to set the maximum attenuation. The modified spectrum is applied to the suppressor grid 78 of pentode 79, the gain of which is controlled by the value of control vvoltage applied from D.C. source 87.

The pentode 79 corresponds with the gain controlled phase reverser 65 of FIGURE 7,V resistance 75 being an vadding resistance for signal applied directly from input terminal 70, and signal applied via filter network 90 and phase reversing pentode 79.

' denotes an input terminal and the reference numeral 101 an output terminal. A relatively high resistance 102 is connected in series between input terminal 190 and output terminal 101.

Connected between input terminal 100 and ground is a potentiometer 18S, the slider 106 which is connected to a filter network 108. The latter includes two shunt legs and a series capacitor 107. Each of the legs consists of one of resistances R1, R2, in series with one of capacitors C1, C2, the values of which, in conjunction with the value of capacitor V167, set out in the drawings, are selected to provide swell shutter effect in conjunction with the rest of the circuit.

The filter network 188 provides signal to the suppressor grid 110, which operates as a signal input grid of a pentode 111. A D.C. gain control voltage derived from variable D.C. source 112, (including the potentiometer of a swell shoe) and applied via a relatively large resistance 113, is connected in series to control grid 117, resistance 113 serving in conjunction with shunt capacitor C3 as a delay circuit for D.C. gain control voltage in the bias circuit.

The pentode 111 includes an anode 115, a screen grid 116, control grid 117 and a grounded cathode 118. The screen grid 116 is connected to a fixed positive voltage terminal 120. The anode 115 of pentode 111 is resistance loaded, by resistance 124, and is coupled to output terminal 101 through D.C. blocking condenser 125 and isolating resistance 12d. Series resistance 123 and capacitance 129 compensate for stray capacity at the adding point, terminal lili. l

In operation the system operates according to the principles governing the circuit of FGURE 7, i.e., a direct path exists for input signal, in parallel with a phase inverting gain controlled filtered path, the two paths being additive in resistances 102, 126.

The phase inverting gain control path includes a swell shutter complementary attenuation network, in cascade with a phase reversing pentode 111, which is subject to remote'gain voltage from variable bias source 112. As the bias voltage supplied by the latter is varied between values of 0 v. and 5.5 v. the gain ofthe pentode is controlled between maximum and cut-off.

In the system of FIGURE l0, which corresponds broadly with FIGURE 9, the voltage at screen grid 116 is shown as regulated by a gas filled regulator tube 130. The voltage across potentiometer 131, of variable D.C. voltage source 112, is illustrated as deriving from a fixed voltage terminal 132, via a voltage divider comprised of resistances 133, 134 in series. These differences between the embodiments of FIGURES 9 and l0 are of themselves minor. The primary distinction between FlGURES 9 and l0 resides in the utilization of a cathode follower tube 14) as an adding network. The cathode follower tube 140 includes an anode 141, a control grid 142, and a cathode 143 connected to ground via an unbypassed cathode load 144.

The grid 142 is fixed biased from a voltage divider con- -sisting of resistances 145, 146, connected between B+ terminal 147 for tube 140 and ground.

The grid 142 of tube 140 is supplied with signal via isolating capacitor 147 directly from slider 186 and also from the anode 115 of pentode 111. The latter circuit proceeds through an isolating capacitor 150 and a signal combining resistance 151.

The mode of operation of the system of FIGURE l0 follows closely that of FIGURE'I 9, and is not, accordingly, repeated.

While I have described and illustrated one specific embodiment of the present invention, it will become apparent that variations ofthe specific details of construction may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

Iclairn:

1. In an electronic organ, a plurality of tone generato-rs, means comprising key switches for selecting tones deriving from said `tone generators, formant filters connected :to said key switches for forming selected ones Y of `said tones, an expression pedal actuated gain control radiator in casca-de with said amplifier, a volume control :device for controlling the amplitude versus frequency characteristic of said amplifier, said vol-ume control device having a controllable amplitude versus frequency characteristic having a variable slope magnitude extending between zero and at least five decibels per decade over said aud-io band.

2. A volume control circuit for an audio frequency band, said volume control circuit including two parallel paths, only one of said paths including a volume control network yhaving a predetermined attenuation ver-sus frequency .characteristic such that said paths together' have a slope magnitude of `the order of seven to ten decibels per decade over said audio frequency band, and means for diferentiallycombining the responses of said paths.

3. A tone control circuit according to claim 2 wherein said means for differentially combining includes a phase reverser in one of said paths and means for additively ,combining the responses of said paths to said audio frequency band.

4. A volume control system for an electronic organ, for `simulating the frequency response -characteristic as a function of shutter position in a pipe organ, comprisinga volume control network, said volume control network` includingA a first path extending from a signal input terminal to a signal output terminal, a plurality, of paths extending in s-hunt to said rst path, said shunt rpat-hs each cons-isting of resistance and capacitance in series, said shunt paths having each a different time constant, the slopes of the frequency response versus attenuation characteristics of the separate shunt paths providing in -sum a substantially linear frequency response versus attenuation characteristic having a magnitude of the order of seven to ten decibels per decade over the audio frequency range.

`5. The combination according to claim 4 wherein is provided a variable impedance in series with said -rst path.

r6. The combination according to claim 4 wherein is provided a variable impedance in series with all said shunt paths.

7. A volume control system for an electronic organ, for .simulating the frequency response characteristic as a function of shutter position in a pipe organ, including a volume control network, said volume -control network including a vfirst path and a second path in parallel between an input and output terminal, said first path having essentially a flat frequency response characteristic, said second path having a sloping frequency response characteristic, the algebraic sum lof said characteristics` being such Vas to provide a substantially linear frequency response versus attenuation characteristic having a magnitude of the order of 4seven to ten decibels per decade over the audio frequency range.

i8. The combination according to claim 7 wherein said second path includes a gain controllable amplifier.

9. The combina-tion according to claim 8 wherein isprovided a source of variable D.C. gain control voltage, and means for applying said variable D.C. gain control voltage in gain control relation to said gain controllable amplifier.

10. lThe combination according to claim 9 wherein said second path includes a filter having a `series capacitor and a plurality of shunt paths each consisting of resistance and capacitance in series, said shunt paths having each a different time constant.

V11. -A volume control circuit, comprising an audio band signal input terminal, a potentiometer having an end terminal connected to said input terminal and having a slider, a pentode vacuum tube having a suppressor grid and a control grid, a network having a predetermined su'bstantially linear attenuation versus frequency decade characteristic over said audio band, means coupling said network between said slider and said suppressor grid, an anode load for said pentode, a further circuit having a substantially flat frequency response characteristic over said audio band and having one termination connected to said slider, an adding network, said further circuit having another termination connected to said adding network, means coupling said anode l-oad to said adding network, and means for varying a bias voltage for said control grid between Zero gain condition and a condition of predetermined positive gain.

`12. A volume control system for an audio frequency band, comprising a main path for said audio frequency band extending between an input terminal and an output terminal, a plurality of shunt paths extending from said main path, -said shunt pat-hs including one resistive branch and the remainder including resistance a-nd capacitance in series, and all .hav-ing widely different time constants, and a variable control impe-dance in series with said main path, said shunt paths having high impedance at a frequency below c.p.s. for all values of said control impedance, said control impedance being adjustable to linearly vary the slope of the gain per decade of frequency characteristic of the combination of said shunt paths.

13. A volume control circuit for an audio frequency band, comprising a first path, a second path, said first and second paths extending at least partly in parallel between -a single signal input termin-al and a single signal output terminal, one of said paths having essentially a flat transmission characteristic as o function of frequency, the other of said paths having a transmission characteristic of substantially linear slope per decade of frequency, means foi-.differentially combining the outputs of said paths at said output terminal, and means for varying the gain of said other of said paths between zero gain condition and a predetermined maximum gain condition.

14. The combination according to claim V13 wherein said means for varying the gain of the other of said paths includes a gain controllable amplifier and a source of gain control voltage applied to said amplifier. v

15. The 'combination according to claim 14 wherein said 4source of grain control voltage :includes a source of variable direct voltage, and aV lead extending from said source cf variable direct voltage to said amplifier, and wherein is provided a time delay network in circuit with said lead, said time delay network including a `series resistance and a shunt capacitance, said shunt capacitance having low impedance for all audio frequencies.

16. A volume control system for an audio frequency band comprising, in combination, an input circuit for audio frequency signals, means for -combining audio frequency signals, sai-d -combining means having a plurality of inputs and an output, ya first electrical circuit coupling said input circuit to one of said inputs of said combining means, a second electrical circuit coupling said input circuit to another of said inputs of sai-d combining means, said -rst electrical circuit having la substantially fiat frequency response characteristic, saidrsecond electrical circuit including means for controllably varying the gain condition thereof as a function of frequency to produce a substantially linear sloping frequency response characteristic Iof gain versus frequency decade therein.

1-7. The combination according to claim 16 wherein .said means for controlling gain as a function of frequency includes a plurality of paths shunting said second electrical circuit, each of said shun-t paths comprising resistance and capacitance lin series circuit, each of said shunt paths having a separate preselected frequency response characteristic, and means for adjus-tably and linearly varying the overall frequency response characteristic of said paths in terms -of gain per frequency decade.

18. The combination according to claim 17 wherein said second electrical circuit further includes a gain controlled amplifier coupled to said shunt paths, a source of variable direct voltage, and means for applying said direct volt-age to said gain controlled amplifier.

19. The combination according to claim 18 wherein said means for applying said direct voltage -to said amplifier includes a time delay network eomprisi-ng a series resistance and a shunt capacitance, said shunt capacitance having low impedance for all audio frequencies.

References Cited by the Examiner UNITED STATES PATENTS 2,037,753 4/'36 Barton.

2,078,762 4/37 Holst B30-151 `2,179,414 1l/39 Konkle 33o-151 X y2,439,198 4/48 Bedford S30-70 X` 2,493,358 1/50 Oswald 241.19 2,578,541 12/51 Hammond 84-1.27 X v2,638,501 5/53 Coleman S30-151 2,760,011 8/56 Berry S30-151 X 2,802,063 *8/57 IFine et al.

2,982,928 5/61 Kall 333--70 2,988,713 6/61 Fukata 333-70 3,080,532 3/63 `Cunningham S30-131 X ARTHUR GAUSS, Primary Examiner.

ARNOLD RUEGG, Examiner.

NITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,193,609

July 6, 1965 Albert Meyer It is hereby certified tha-t error appears in the above mmbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 60, for "RC L network read RCL-network for "12" read 11 line 48, for

; column 3, line 20, "Peferrng read Referring same column 3, line 75, for

"transfers" read transfer Signed and sealec this 18th day of January 1966.

(SEAL) Attest:

ERNEST W. SW'IDER 'EDWARDL BRENNER Atteeting Uffioer Commissioner of Patente

Claims (1)

1. IN AN ELECTRONIC ORGAN, A PLURALITY OF TONE GENERATORS, MEANS COMPRISING KEY SWITCHES FOR SELECTIVELY TONES DERIVING FROM SAID TONE GENERATORS, FORMANT FILTERS CONNECTED TO SAID KEY SWITCHES FOR FORMING SELECTED ONES OF SAID TONES, AN EXPRESSION PEDAL ACTUATED GAIN CONTROL DEVICE IN CASCADE WITH SAID FORMANT FILTERS, AN AMPLIFIER IN CASCADE WITH SAID GAIN CONTROL DEVICE, AND AN ACOUSTIC RADIATOR IN CASCADE WITH SAID AMPLIFIER, A VOLUME CONTROL DEVICE FOR CONTROLLING THE AMPLITUDE VERSUS FREQUENCY CHARACTERISTIC OF SAID AMPLIFIER, SAID VOLUME CONTROL DEVICE HAVING A CONTROLLABLE AMPLITUDE VERSUS FREQUENCY CHARACTERISTIC HAVING A VARIABLE SLOPE MAGNITUDE EXTENDING BETWEEN ZERO AND AT LEAST FIVE DECIBELS PER DECADE OVER SAID AUDIO BAND.

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