JPS61242499A - Microphone apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to automatic microphone control suitable for use in sound enhancement, recording, broadcasting, remote or microphone conferencing, and other applications.

BACKGROUND OF THE INVENTION For reasons such as the large number of participants or the number of locations from which a single sound needs to be picked up, multiple microphones are often used.

The outputs of these microphones are typically combined in a mixer circuit and fed to a sound intensifier, a recording device, or a transmission link for transmission to a remote location. When a conventional fender is used with multiple microphones, the amount of room noise and echo reception or capture increases compared to a single microphone. The tendency for knowing also increases even if, for example, only one or two microphones are receiving valid acoustic input (speech) at any given time. Such matters are explained by Stefan Gjelström (
Direction Sensitivity Deguting: A New Approach to Automatic Mixing (Dire
ction-8intensiveGating: A
New approach to automation
cMixing) J, JAE Volume 8.32, Issue 7/8, 1984, July/August.

More recently, automatic mixers have been used to "gate" on (pass to the mixer output) only those signals from microphones receiving useful acoustic input. The relative efficiency of these mixers is primarily a function of the means used to determine when to gate the microphone on. Microphones should be gated on quickly and independently in response to valid speech or voice input over a wide dynamic range. However, the microphone should not respond to background room noise or to speakers who would be better received by other microphones. Additionally, for the proper operation of many microphone conferencing devices, including devices or systems used in the applications described above, it is necessary to activate the gate to the on state of the microphone at a room loudspeaker that generates sound from a remote location. Shouldn't.

Gating methods that rely on signals emitting microphone output levels above a fixed threshold level do not meet any of the criteria mentioned above. There have been documents suggesting various gate methods. For example, Duga
n) US Patent No.! According to the technique disclosed in US Pat. The configuration is such that it tracks an estimate of background room noise based on distance samples sampled from. In this way, it is possible to improve the gate function sensitivity while avoiding response to room noise.

Breeden U.S. Patent No. 3751
No. 602 discloses a gating function for a simple tx microphone used in a Sugi-Cajon (simple microphone conference system). According to this US patent:
A noise reference signal is taken from a single microphone and its level signal is processed by a very slow rising and fast falling circuit. In most interior acoustic environments, additional circuitry is provided to inhibit the microphone from being gated on for loudspeaker sound.

“VX Maston U.S. Patent No. 37556
No. 25, only one of the plurality of microphones is gated on at any given time.

In order to perform this gating to the on state (and thus gating the already on state of the microphone to the off state), the microphone level must exceed a fixed threshold and e.g.
The level of the microphone that is already on must be exceeded by a preselected amount, such as dB.

U.S. Pat. No. 4,099,025 to XAHN discloses that the Disclosed is a technique that prevents the triggering of all microphones for a period of time plus a short additional time corresponding to the time it takes for a sound wave to propagate to the farthest microphone in the system. be.

8chrader U.S. Patent No. 409
No. 0032 discloses a technique for disabling the threshold as soon as the level of at least one microphone exceeds a presettable fixed threshold and is gated on. In this case the threshold is the highest level,
Approximately the output level of the microphone gated on-state varies between the maximum level and the output level of the microphone gated on.

Even in the case of multiple sound sources, it is strictly prohibited for more than a few microphones to be gated on at the same time.

Anderson et al. U.S. Patent No. 4
No. 489,442 (assigned to the present applicant), each "microphone" actually consists of an array of typically two unidirectional microphones mounted in back-to-back relationship within a common housing; #The output levels of the two microphones are compared. The level of the "front" microphone exceeds the level of the "rear" microphone by a predetermined amount, typically 9.54 aB (representing that the sound source is within an "acceptable angle"). If exceeded, the gate function to the on state is triggered by the front microphone or the front microphone signal.

According to the construction of the above-referenced Anderson patented invention (which also forms part of the preferred embodiment of the Gelstrom US patent application cited above), the noise level of the room at the location of the microphone is inherently about 5. A dB higher effective gate threshold is set. This Anderson configuration provides direction-sensitive gating, thereby limiting the number of microphones that are gated on for rear sound sources without causing gating of any microphones on; Preventing desired gating of other microphones for other sound sources. Also according to this Anderson configuration, the loudspeaker of the microphone conferencing system is configured such that the loudspeaker of the microphone conferencing system is configured such that it does not trigger the gating of any microphone to the on state and does not inhibit the desired gating of local speakers. positioning of loudspeakers.

However, the principle of operation of Anderson's device requires some care in the placement of microphones and loudspeakers. Anderson's device also allows a single sound source to gate or trigger multiple microphones at overlapping reception angles. Furthermore, the Anderson system typically requires two high quality matched transducer elements for each microphone, even if only one pair of microphones is used. Most notably, according to Anderson's configuration, proper gating operation may be inhibited by acoustically reflecting objects in close proximity to the rear of the microphone, or alternatively by microphones placed very far from the sound source with respect to the room's reverberant field. This means that the microphone cannot accurately evaluate the direction of the sound source.

For purposes of explanation, it is assumed that the sound that a microphone "picks up" in a room consists of two parts. That is, the direct sound whose level decreases by 6 (IB) as the distance from the source doubles, and the reverberant field coming from all directions which spreads substantially homogeneously throughout the room even as it decays.

The directional gating function works satisfactorily if the microphone is not located so far from the sound source that there is primarily a reverberant field at the microphone's sound collection location. In large rooms, a dominant echo field will not occur unless the speaker is five feet or more from the microphone. However, at this distance, the pickup function of the microphone may be degraded and may become unidentifiable.

In small rooms, such as offices and many conference rooms, the reverberation field can become dominant even at distances of two feet or less, making it difficult to use the conventional speaker-to-microphone distance direction-sensing microphone method. Even if used, proper gating function would be prevented. However, compared to large rooms, in many such small rooms, the pickup or collection quality of the acoustics is quite good even when reverberations are dominant, yet the reverberations occur relatively quickly. Sensory acceptable for attenuation. However, one microphone can be used if properly gated.

None of the prior art disclosed in the patents cited above
Achieve maximum gating sensitivity in the presence of varying background room noise, prevent multiple microphones from being gated on for a single talker, and reduce mutual inhibition to Allows a speaker to gate multiple microphones on at the same time, and accomplishes this even when operating in a generally reverberant acoustic environment (e.g. a small room) It does not set out any goals or attempt to solve any such goals. Furthermore, the microphone must not be gated on by sound from the conference equipment's loudspeaker, yet the desired gating function for simultaneous local audio or speech is significantly inhibited even in highly reverberant environments. Shouldn't.

OBJECTS OF THE INVENTION Accordingly, it is an object of the present invention to provide an automatic microwave dart method that maximizes sensitivity to speech while suppressing sensitivity to varying background room noise.

Yet another object of the invention is to provide a method that allows only the single most suitable microphone in the system to be gated on for a single speaker.

Another object of the present invention is to provide a method that allows multiple speakers to gate multiple microphones on at the same time, thereby minimizing mutual inhibition of IC gate functions.

It is another object of the present invention to provide a method for preventing conference equipment loudspeaker sound from gating the microphones to the on state while minimizing the inhibition of gating the desired microphones to the on state for locally generated audio. It is about providing.

Another object of the invention is to provide a method which makes it possible to achieve all the above-mentioned objectives even in a small room acoustic environment with reverberation close to total internal reflection.

Another object of the invention is to provide a method that makes it possible to create a "dead zone" within a room in which a sound source does not trigger the microphone gating function.

Another object of the invention is to provide a method that allows microphone gating information to be used to control other functions such as automatic video camera switching.

Yet another object of the invention is an automatic gain adjustment means for maintaining a constant amount of reverberation field collection even when the number of widely spaced microphones gated on varies over a range greater than zero. The object of the present invention is to provide a method for associating the method with the gate method.

Still another object of the present invention is to maintain constant reverberation field collection or reception even when the number of closely spaced on-state VC gated directional microphones varies over a range greater than zero. K provides an apparatus equipped with automatic gain adjustment means.

Yet another object of the present invention is the use of the gating method disclosed herein in a conferencing device having the benefit of the invention of the Djurström patent application cited herein.

Still another object of the present invention is to make optimal use of the characteristics of the gating method, to be easy and simple to set up, and to enable improved acoustic collection or reception and generation through optimized acoustic and electrical design. The objective is to use a loudspeaker/microphone combination in conference equipment that operates in almost any acoustic environment and is easily expandable.

SUMMARY OF THE INVENTION The above-mentioned objects, as well as other objects, utilize a processing circuit responsive to rapidly changing DC levels that accurately represents the frequency equalized output of each microphone, and in a conference equipment application, a loudspeaker. This is accomplished by embodiments of the present invention using electrical drive signals that are similarly equalized for .

Each microphone circuit block of the preferred embodiment of the present invention processes DC level signals by using very slow rise and fast fall (attenuate) circuits to generate a noise adaptive threshold (NAT). This threshold can be adjusted to the background noise level present during short pauses in speech;
There is no need to specifically respond to the audio waveform. To meet the NAT criteria and potential gating criteria, the microphone's DC level signal should be NA'l' (6 dB) just large enough to protect against false triggers due to random background noise fluctuations. must be exceeded.

In this way, a high gate sensitivity (low threshold) for speech is possible even in the presence of noise in the room, which can be further improved by using a directional microphone. In a conference device according to a preferred embodiment, the microphone typically rejects reception of 5 to 7 dB of room noise compared to a direct audio receiving microphone. Therefore, only direct speech gates the microphone on at the measured room noise level (level measured by a standard omnidirectional noise measurement device).

The NAT gate criterion also applies to microphones placed in echogenic areas found in small to medium-sized conference rooms with poor acoustics, even without the extra sensitivity afforded by directional microphones. (Microphones are typically not used in highly reverberant fields in very large rooms, where they have very long echo onsets and slow decay rates that create problems with gate functionality.) (This is because the sound collection capabilities of directional microphones used at a reasonable distance from the sound source in such environments are not acceptable.)

To prevent multiple microphones from being gated on for a single speaker, a second criterion ( MAX bus line) must be satisfied.

This side α bus represents the changing dC level equal to the difference reduced by a fixed amount of 6 dB for each of the microphones that are gated to the off state from the maximum value of the changing dc level signal of each of the microphones that are gated to the on state. Maintain the individual system! There is a single connection between the microphone circuits.

In order to satisfy the MAX bus standard, the microphone circuit block must at least momentarily "hold" the MAX bus.
The maximum voltage must be applied to the AX bus).

A microphone is gated on only if the MAX bus and NA'I' criteria are simultaneously satisfied for that microphone. Once the two criteria are satisfied simultaneously, a re-run for a "hold time" of 0.4 seconds is sufficient to bridge the gap in the bird and the pause period between words. A trigger signal is generated by a triggerable one-shot circuit. The downstream circuit is
In order to improve the main effect of the gating function, the onset speed and attenuation or fall speed of the acoustic signal switching is controlled. Such trigger and switching rate control circuits are substantially the same as those disclosed in the above-cited patents of Anderson et al.

Although not necessarily necessary in many cases,
According to one preferred embodiment of the invention, all the same microphones are used, all operating at the same relative gain, differing only in their configuration or orientation and position relative to the various sound sources. The speaker's voice reaches the microphone closest to the speaker (the microphone best suited to receive the speaker's voice) and gates that microphone on. (If the microphones are not the same, are operated with different relative gains, and are placed very far apart or very close together, the relative levels of these microphones become an important factor in addition to their relative arrival times.) (However, even in that case, the microphone best suited to pick up the speaker's voice would be gated to the on state.) The microphone that was gated to the on state would be gated to the off state on the core bus. The gain is immediately exceeded by 6 dB for that microphone, which effectively prevents other microphones from being gated on for that speaker. This 6 dB gain, combined with the time constant of the filter and the characteristics of the VcDC level signal circuit, is sufficient to reduce the impact of a shocking sound or a sound that terminates abruptly (at a far-field microphone) and all at approximately equal levels. Even in the case of attenuated reverberation reaching the microphone of the speaker, the microphone is prevented from being gated on secondarily (for the speaker in question). 6 for microphones that are on
4B7'1 Given the large gain, the filter time constant, set to 11 ms, ensures that the off-state microphone is not gated to the on-state in the reverberant sound so that the sound ends abruptly and is spaced apart. small enough to reliably prevent triggering of microphones in the system.

Thus, a single speaker can gate only one microphone on, and multiple speakers speaking in a normal manner are required to optimally pick up their voices. To reliably gate multiple microphones in an on state. The use of precision full-wave rectification followed by low frequency attenuation in obtaining the DC level signal of the microphone output improves the filter's rapid time setting 1t(i1
milliseconds). Typical speech patterns have peaks, minima, drops, and pauses that are accurately represented by rapidly changing corresponding DC levels. Since multiple speakers cannot synchronize these variables, there is often an opportunity for each speaker's closest microphone circuit to temporarily "hold" the MAX bus, which may trigger the gating function. The rapid C level change from each voice is typically much larger than the difference in average level between individual voices. Therefore, even if a loud speaker is simultaneously speaking into another microphone that is in the on state, the quiet speaker's microphone circuit will maintain the alpha bus, thereby gating the quiet speaker's microphone in the on state. I can do it. This is not changed by the 6 dB gain height given to the already on microphone on the MAX bus. This is because this 6 dB gain height is small compared to the microphone level change.

However, a gain height of 6 dB means that a microphone that is already on will remain on even if the speaker gets slightly close to a microphone that is gated off.

A "speaker inhibit signal" is generated to prevent the sound from the teleconference loudspeaker from gating the microphone on. This loudspeaker inhibit signal is a rapidly changing DC level (substantially the same as previously described in terms of frequency) of the loudspeaker electrical drive signal. This speaker inhibit signal is calibrated or scaled to approximately represent the worst case (best) DC level signal expected from the microphone due to the sound generated by the loudspeaker.

It is possible to apply such a power inhibit signal to the Y6 or MAX bus used in the direct microphone level comparison to prevent the microphone from being switched or switched by the sound received directly from the loudspeaker. can. This loudspeaker inhibit signal is (
Minimal impact on desired microphone switching for simultaneous local audio (required to accommodate remote speakers).

However, in practice, in most rooms there can be enough energy that the microphone is triggered by the reverberation of the loudspeaker sound after the speaker inhibit signal applied in this way has disappeared. To prevent erroneous microphone gating or switching, the attenuation of the speaker inhibit signal must be increased by several tenths of a second or longer (possibly much more, especially in a room with poor conditions). ) will need to be made longer. In this way, rapid level changes are removed from the signal making it very difficult for an on-going speaker to gate the microphone on.

Alternatively, the speaker inhibit signal is applied to each microphone's NAT in a special manner with its rapid level changes; The action of whichever is larger can cause a "hold J" (same meaning as used in connection with the MAX bus). The microphone should be properly calibrated or referenced to prevent switching and have a fast time constant to minimize inhibition of switching of the W microphone to allow for excellent speech compatibility. maintained.

However, speakers are prohibited at the NAT level! This is not the maximum value of the original NAT level. When the speaker inhibit signal decays, the modified NAT level is no longer the same as the level it was before the speaker inhibit signal was applied. The modified NAT follows the speaker inhibit level which decays until it reaches the level of the microphone output, and then follows the level of the microphone output in normal NAT operation. In the absence of local audio, the microphone acoustic input that immediately follows the decay of the speaker inhibit signal is the reverberation of the loudspeaker acoustics.

This reverberation is 6dB+7) even in the case of uneven reverberation.
By tracking the actual reverberation of the room, which will not trigger microphone gating or switching because the microphone level vs. Safety design margins based on the most unpredictable room acoustics are no longer required, and sensitive local isolation capability can be maintained over the full range of available room acoustics. The Sugiichiriki prohibition function is for NAT and M
It can be advantageously used with multiple microphones in conjunction with the AX bus or, as will be discussed below, with a single microphone in conjunction with the NA'r without the box bus.

The microphone dart system disclosed herein can be used with various additional circuits to construct a teleconferencing system, such as that disclosed in the above-cited Djulström patent application. Its properties can be exploited in the most advantageous manner when used as part of a material. In this way, the benefits of the system described above, including overall system gain and feedback control in transmit/receive direction switching for sensitive, high-speed speech, can be achieved even in small, acoustically poor rooms; Furthermore, configuration requirements are reduced.

In the preferred embodiment disclosed herein, small upward-facing loudspeakers are arranged circumferentially and evenly spaced in a common low-profile (small height) mounting or module. Surface mounting is combined with a directional microphone. Used in this manner, the acoustic design provides smooth, wide-range sound pickup as well as without the frequency response deviations normally encountered when acoustic transducers are used in the vicinity of reflective surfaces. The loudspeakers distribute the sound evenly to all conference participants located around the module. In combination, the microphones significantly reduce the collection or reception of room noise and reverberation compared to conventional single forward-facing microphones.
Sound can be captured substantially evenly around the module.

Additionally, directional microphones are placed around the loudspeaker in a manner that maximizes rejection of direct loudspeaker sound. Even taking into account the strong reflections of the loudspeaker sound from objects in close proximity, this embodiment of the invention provides a system with However, some reduction in the feedback control suppression setting and speaker inhibit signal level (as disclosed in the related Jullström patent application) is possible. The loudspeaker/microphone module is
They can be used singly or "chained" for better acoustical coverage of long tables or multiple tables.

Connections between modules are made via a single multi-conductor cable. This cable transfers, among other things, the output of the gated microphone, the MAX bus, and the loudspeaker power amplifier drive signals. Even in this case, the single microphone closest to the speaker is gated on with the speaker's voice.

Depending on the user's wishes, a module can be 'muted'. This will prevent the microphone's audio signal from being gated to the on state, but the circuitry will be muted when the microphone is gated. This muting feature creates a "deadband region" around the muted module, in which conversational audio and other unwanted sounds (such as paper rustling) will not trigger the microphone to be turned on, thus not interrupting the teleconference. Needless to say, this muting effect can also be applied to a single microphone.

A variation that may be adapted for teleconferencing or general use is to place multiple directional microphones very close to each other, instead of placing the microphones far apart, thereby eliminating most Over a range of frequencies, sound waves from various directions can be made to arrive at the microphone with substantially the same phase. Under these conditions, new polar directional patterns are formed as different combinations of microphones in the array or play are gated on. Essentially, the arrangement or play forms a single microphone whose polar directivity pattern and orientation are automatically adjusted to optimize the pickup or collection of the voices of speakers around it. I can say it.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiment Referring to FIG. 1, one embodiment of the microphone-cord system is shown in this figure. In this conference system, the diameter of the conference table 13 placed at the center is approximately 1 foot) (
25.4 cut) microphone/loudspeaker device 11. The microphone/loudspeaker device 11 is connected to the control device 15 of the conference device by a cable 35 passing through a hole drilled in the table or placed on the side of the table.

The control unit 15 is connected to a telephone line jack 19 by a conventional telephone line 31 for a conventional "two wire" connection. Telephone 17 is also connected to control device 15 by telephone line 33 . The user uses the telephone 17 or the microphone/
Any of the loudspeaker devices 11 can be automatically connected to the telephone line jack 19 along with associated circuitry within the control device 15.

Although shown as being connected to a two-wire link (combined transmit/receive path), the system or device may also
It can also be used with a 4-wire link (separate transmit and receive paths) as described in the patent application of Ström. The 4-wire link can be a hard wire, or it can also be a wireless or satellite link, which can include a time delay. The wireless link could be a mobile telephony wireless link. It would also be possible to employ a more suitable physical constellation of microphones and loudspeakers than those described below.

As shown in FIGS. 2 and 6, the microphone/loudspeaker device 11 includes six outward facing unidirectional ( It is equipped with cardioid-shaped microphones 21, 23 and 25. The base 2T has a flat, almost conical shape as shown.
They are arranged at the acoustic zero points of 1.23 and 25, and are attached upward to the base 2T in plane parallel, as shown. The base 2T is preferably placed on the top surface of the conference table 13.

With such a mounting, the microphones 21, 23 and 25 operate very close to the surface so that acoustic interference from the base 27 is minimized. Also, loudspeaker 29
behaves essentially the same as if it were mounted in concave relation to a large flat surface. As also stated in the cited document, microphones and loudspeakers can in this case have a smooth and even frequency response over the entire audio range without the negative effects normally caused by Ciedele surface reflections. . Furthermore, the directivity of the microphone and loudspeaker is 3.0 (compared to free space).
Increased by an amount close to aB, the clarity of audio pickup and playback is improved. The horizontal dispersion of a loudspeaker's sound is primarily due to its small dimensions (approximately 2 inches or 5 inches).
．． 08cIrL diameter cone), "beaming" is suppressed to a minimum.

Each microphone 21-25 is typically kept off (open circuit) until needed to reduce unwanted sound pickup (room noise, reverberation, and loudspeaker sound). A microphone is automatically gated on (closed circuit) only if it is the closest microphone to a source of speech-like sound other than a loudspeaker. The microphone is not gated on for room noise or loudspeaker generated sound.

If no local audio is present, the microphone is turned off and the acoustic coupling path from the loudspeaker to the microphone is completely interrupted.

Loudspeaker sound reverberations or echoes do not return to the farthest end of the communication link. Microphones can be switched on quickly and reliably in response to speech without cutting out syllables or words, and can be switched on quickly and reliably.
+! Due to the directivity of the microphone in relation to the acoustic arrangement of the microphone and the microphone, acoustic coupling of the loudspeaker and pickup of room noise and reverberations while the microphone is gated on is minimized. Ru.

Several devices 11 can be used along the conference table 13. As already mentioned and as will be explained below, two or more devices 11 can be electrically cascaded.

Referring to FIG. 4, the microphone/loudspeaker device 11 includes a microphone/speaker circuit 41, and the control device 15 includes a control circuit 43. The microphone/speaker circuit 41 receives signals from the microphones 21-25,
In response, gated microphone signals and non-gated microphone signals are generated on respective conductors 45,47. The microphone signal is received by a control circuit 43 which generates a transmit signal for transmission to a wall jack box or unit 19. The acoustic information received by jack unit 19 is used by circuit 43 to generate a speaker signal on conductor 49. The speaker signal on conductor 49 is received by microphone/speaker circuit 41 to drive loudspeaker 29.

Control circuit 43 may be constructed using circuits according to the preferred embodiments described in the related patents cited above. In particular, the microphone 11, microphone interface/
Gate circuit 353, output amplifier 321 and loudspeaker 13
can be replaced by the microphone/loudspeaker device 11 of the invention. The gated microphone signal is transmitted on conductor 358 of the related application and the non-gated signal is transmitted on conductor 1 of the related application.
003 can be applied. The input signal may be derived from the output of the mixer/limiter stage 334 of the related patents. As will be appreciated, other types of control circuitry could be used as circuit 43 to transmit microphone signals and receive loudspeaker signals over telephone lines or other telecommunications links.

Julstrom A quoted earlier
The control circuit 43, described as a preferred embodiment of the invention in the patents of 1999, is necessary to maintain the stability of the feedback by gating the microphone on with local conversational audio. Suppressing (attenuating) the loudspeaker level when blocking only to a certain degree 9 When local speech is blocked at the farthest end, the output microphone signal is suppressed and the loudspeaker can be heard at normal level.

The circuit of the referenced patents also determines transmit/receive direction switching for suppression as required in non-disruptive interactive conferences. When both terminals start speaking at the same time, priority is given to the party blocking the conversational audio to maintain a smooth dialogue. Both terminals can be accessed without making loud noises.

The combined microphone signals from all on-gated microphones are routed to device 15 via conductor 45.
is supplied to the control circuit 43 of. Before the gated microphone signal enters a conventional hybrid circuit for transmitting the microphone signal to the telephone line via jack 19,
It can be passed through a current controlled amplifier (as described in the cited patents). As described in the cited Gerström patents, the control current input to the current controlled amplifier is highly controlled by the transmit/receive direction determination.

Potential feed bar cruciform gain instability is often controlled by providing suppression in the transmit path during receive mode and in the receive path during transmit mode.

There are currently commercially available devices available for transmitting a gated microphone signal to a telephone jack 19 for transmission to the far end of a telephone communication link and for extracting a received signal from the telephone jack 19 for transmission to a loudspeaker 29. It would also be possible to use some number of circuits as control circuit 43. Microphone/speaker circuit 41 uses a different gate structure than that described in the referenced Gelstrom patents. This will become clear from the subsequent description in connection with circuit 41.

Referring to FIG. 5, the microphone/speaker circuit 41 includes a gating circuit 50 consisting of three similar microphone gating circuits 51, 53, and 55 associated with each microphone 21, 23, and 25. A conventional power amplifier 59 responds to the loudspeaker signal from control circuit 43 appearing on conductor 49 to generate a Kabel-like signal on conductor 58 sufficient to drive loudspeaker 29 . Prohibition signal generator 57
receives the loudspeaker drive signal from conductor 58 and responsively generates an inhibit signal to each gate circuit 51, 53, 55. Each gate circuit 51, 53, 55 is similar in structure and therefore only one gate circuit will be described in the description with reference to FIGS. 6-12.

The MAX bus conductor 56 interconnects the microphone gate circuits, but is not required to connect the control circuit 43, as described below with reference to FIGS. 6 and 11.

Referring to FIG. 6, the microphone 21 is a preamplifier/
It is electrically connected to the interface circuit 61.

After the pre-amplification, the microphone signal is output to the conductor 47 as a non-gated microphone signal, and is output to the conductor 4 as a gated microphone signal via the onotic coupler switch 69.
5 is output.

The remaining circuit portion of FIG. 6 is completed by generating an ozotic cazola control signal on conductor 71 leading to the onotic coupler switch 69.
Controls operation (opening/closing operation). The signal on conductor 71 is (
i) the pre-amplified microphone signal of the associated microphone (appears on conductor 73); (2) the signal associated with the other microphone (appears on MAX bus 56); (3) the loudspeaker drive signal (appears on conductor 58). (appears on conductor 75) and (4) mute logic signal (appears on conductor 75).

The microphone signal on conductor 73 is provided to trimmer circuit 81 . This circuit 81 is connected to the related microphone gate circuit 51
(FIG. 5) so that each of the three microphone/gate circuits 51, 53, 55 is the circuit used to operate similarly in the comparative analysis described below.

The microphone signal is then provided to a frequency equalization/rectification circuit 83 having a frequency that equalizes the acoustic signal. The low frequency component has its level reduced relative to the intermediate frequency, and the high frequency component also has its level reduced relative to the intermediate frequency, although to a lesser extent than the low frequency component. The circuit 83 serves to accurately full-wave rectify the acoustic signal and filter the resulting signal. The output of circuit 83 is connected to associated microphone 21
is a varying DC voltage level signal that carries information regarding the amplitude and time of occurrence of the speech signal received by the speaker and the noise in the room.

The output of circuit 83 is fed to a noise adaptive threshold circuit 85 which generates a threshold voltage level representative of room noise in the vicinity of microphone 21.

This circuit 85 generates the threshold voltage level by effectively tracking the DC microphone signal with a very slow response followed by immediate decay. As the DC microphone level signal increases, the capacitor becomes larger
It is charged slowly over a time constant C, and when the DC microphone level signal is removed, the capacitor is rapidly discharged at the same rate as the DC microphone level signal decreases. From normal conversation or speech patterns,
The voltage appearing on the capacitor represents the noise in the room. The noise adaptive threshold voltage is constantly maintained such that the noise in the room does not fall below a certain level. During normal conversation or speech, the capacitor does not charge significantly, and the capacitor continuously maintains or discharges to background noise levels during even very short pauses in the conversation or speech.

The DC microphone output of circuit 83 is also fed to an attenuation circuit 87, where the DC microphone threshold is 6 dB (
attenuated by a factor of 2).

The output of attenuation circuit 87 as well as the output of noise threshold circuit 85 are supplied to voltage comparator 89 . Nuclear comparator 89 produces an output signal that indicates that rapidly fluctuating conversation or speech has exceeded a threshold level representative of continuous noise in the room by 6 dB.

Therefore, the output of comparator 89 can be said to represent an independent determination of the one microphone at which speech or conversation is occurring.

As can be understood from the above description, each microphone circuit 51.53.55 (FIG. 5) is capable of transmitting a conversation or speech from a single person or speaker to the microphone 21.23.2.
5, a similar determination is made in each associated comparator 89. Since it is desirable to limit the number of microphones that are gated on for a single sound source, the output of comparator 89 determines whether the associated microphone should be gated on via optical coupler 69. In order to determine, the second determination signal and the ungate 91 perform an AND operation.

A second determination process determines which of the microphones received the highest speech first. Box bus 56 receives inputs representing other microphone signals for use in this second determination process. The MAX bus is connected to a decision circuit 9T in which the other microphone signals are compared with the signals of the associated microphones 21.

The DC microphone signal from circuit 83 is first attenuated by 6 dB reduction circuit 93 before being input to determination circuit 97 . However, this attenuation circuit 93 is electrically controllable from conductor 95 to remove 6 dB of attenuation when the microphone is gated on.

6 dB attenuation circuit 9 that can be disabled like this
The output of 3 is connected to a decision circuit 97 which compares its output with the corresponding signals in other microphone circuits via the Wα bus interconnection and determines all such corresponding signals. It is determined whether or not it is the maximum at the present time. The signal level on the MAX mother a56 is controlled by decision circuit 97 as well as corresponding circuitry associated with other microphones equal to such maximum value.

The noise adaptation threshold criterion is met (i.e. speech is occurring) and the busbar criterion is met (i.e. the associated microphone 21 is now configured with a 6 dB attenuation that can be overridden in each microphone circuit). If the maximum audible speech is received (with some modification) is met, an output trigger signal is generated on conductor 98 to activate a retriggerable one-shot circuit (one-shot multipipelator) 99. . The output of this one-shot circuit 99 activates an optical camera drive circuit 101 which drives an optical coupler switch 69 to gate the microphone signal of the associated microphone onto conductor 45. One-shot circuit 99 provides a hold time of 0.4 seconds after each trigger on its input conductor 98. The output of one-shot circuit 99 is fed back via conductor 95 to the control input of <S dB attenuation circuit 98, which can be disabled. Attenuation circuit 93 responds to a high level signal (HIGH) from one-shot circuit 99 to disable the 6 dB attenuation.

As a result of the MAX bus interaction principle described above, a single speaker will gate only one microphone on, and a normally speaking multi-speaker will certainly gate multiple microphones on. microphone can be gated to the on state.

It goes without saying that the loudspeaker 29 provides audio signals to each of the microphones 21, 23, 25. In order to prevent the microphone channel from being gated by the audio signal from such a loudspeaker, a speaker inhibit signal generator 5T is used. Generator 57 receives loudspeaker drive signal 58 and responsively generates a speaker inhibit signal on conductor 105. Generator 57 equalizes, rectifies and filters the frequency of the loudspeaker drive signal to conductor 10.
5 to generate a DC output. A speaker inhibit signal appearing on conductor 105 is provided to each of the microphone/gate circuits 51, 53, 55.

The speaker inhibit signal is also provided to a noise adaptive threshold circuit 85 for controlling the noise threshold level in the manner previously described and in the manner described below with reference to Figure jIX10. The on-state gating of the microphone in response to the sound generated by the loudspeaker and its reverberations is
77''-) inhibition of the desired microphone on state for local speech is prevented to a minimum.

As is self-evident from the above description, if two or more microphone/force devices 11 are connected in cascade along the upper surface of the aftershock table, all MAX busbars connected together, all loudspeaker output amplifier inputs are connected together to be driven by the loudspeaker signal from the controller 15, and all gated microphone outputs 45 are also connected together, and all The non-gated outputs 4T are also connected together.

Mute person cuff 5, in order to obtain the above results,
7 to 13, all operational amplifiers and comparators It will be appreciated that the power supply is connected to a well-controlled and filtered ±15 volt balanced power supply as is well known in the art. Referring to FIG. 7, the microphone 21 is of an electret condenser type. A transducer is connected to preamplifier/interface circuit 61. This circuit 61
is the field effect transistor impedance exchanger 203 (
Sanyo 25 to 156L), transducer calibration resistor R1, bias resistors R2, R3, preamplifier circuitry R4, R5, C2, C4 and operational amplifier 20
7, and these elements are connected as shown. Resistor R1 is selected to ensure equal sensitivity of each transducer, input transformer, R1, etc. Resistor R5 sets the gain of the preamplifier and is a precision resistor that provides the same acoustic sensitivity from each microphone to the audio mixing bus as well as to the calibration circuit 81. Resistors R7 and R
8 is also a precision resistor.

The microphone signal is transmitted through capacitor C5, photoresistor (
It is passed to the gate microphone conductor 45 via a photoresistor R6 (a part of the onotic coupler 69) and a resistor R7. This microphone signal is also routed to ungated microphone conductor 47 via capacitor C5 and resistor R8.
sent to. The microphone signal is also transmitted via conductor 73 to a trimmer calibration circuit 81, which is described in more detail with reference to FIG. 5 each.
6 is terminated with a grounding resistor of Ω, 1, OK Ω.Therefore, even if a plurality of devices 11 are connected in a link, the value will not change. With such a termination configuration, the amount of background noise and reverberation pickup remains substantially the same even if the number of devices 11 is varied, or even if the number of microphones gated on is varied by a number greater than zero. stay constant. This method is described in the references cited above as well as in the Anderson et al. patent application.

Referring to FIG. 8, the microphone signal is input to trimmer calibration circuit 81 via conductor 73. This calibration circuit 8
1 is an operational amplifier 211 and a tri! A resistor R10 and resistors R11 and R12 are provided, and these elements are connected as shown. Calibration circuit 81 is used to eliminate one element of tolerance to provide a circular microphone input for the MAX bus gain. The trigging action of resistor R1, in combination with a high quality electret transducer, allows precise alignment and control of the gate coverage area of each microphone.

Referring to FIG. 9, frequency equalization/rectification circuit 83 receives microphone signals from circuit 81 via conductor 213. Referring to FIG. Circuit 83 emphasizes the speech or speech portion of the frequency spectrum and attenuates high and low frequency components that deviate significantly from the speech speech band. Also, compared to the energy of the low frequency part of conversation or speech,
Since the high frequency portion of the conversational voice band, for example the voice "8", has low energy, the equalization/rectification circuit 83 emphasizes the high frequency portion of the speech or voice within this frequency band.

The overall result is that the interfering effect of room noise on the gating function is greatly reduced, allowing the use of smaller filtering time constants.

The circuit 83 includes 5 operational amplifiers 21 connected as shown.
5, with resistors R13-R18 and capacitors C7-010. Further, the circuit 83 includes a pair of operational amplifiers 217 and 219 connected as shown, diodes D1-D4 connected to the amplifiers, and resistors R19-
R22 and capacitors C11 and C12 to provide precision full-wave rectification and filtering of the microphone signal.

The operation start time and damping filter time constant are both equal to 11 oriseconds. Circuit 83 provides accurate level sensing over a wide dynamic range, especially in conversational speech. Operational amplifier 221 buffers the output of equalization/rectification circuit 83 appearing on conductor 223.

Referring to FIG. 10, the noise or noise adaptive threshold circuit 85 is shown in detail. conductor 223
The signal appearing at is a linear amplitude representation of the frequency equalized microphone signal. This amplitude representative signal is compared to the voltage appearing on capacitor C13, which is representative of room noise.

The voltage appearing on conductor 223 is applied via field effect through resistor 168 to the non-inverting input of transistor input operational amplifier 225. When the signal at this non-inverting input terminal changes, the capacitor C13 is charged or discharged accordingly.

Resistor R27 is a low value resistor used to ensure operational amplifier 2250 stability and can be ignored in this circuit analysis. transistor Q
102 is connected between the output terminal and the inverting input terminal of the operational amplifier 225, and is used as a low leakage current diode.

When the non-inverting input voltage of operational amplifier 225 is higher than the capacitor voltage, operational amplifier 255 holds its inverting input voltage at the same voltage as the non-inverting input voltage through transistor Q102.

Resistor R2,3 slowly charges capacitor C13 with a time constant of 10 seconds. When the signal at the non-inverting input of the operational amplifier tends to be lower than the capacitor voltage, operational amplifier 225 discharges the capacitor C13 via diode D5. The operational amplifier resolves at a suitable rate according to the feedback voltage appearing at the inverting input via resistor R23. The resistors R2 and R3 are connected to an operational amplifier 2.
A negligible voltage drop occurs due to the low input current of Q102 and the low leakage current of Q102. Discharge diode D5 therefore functions as a precision diode.

In this way, the noise adaptive threshold voltage on capacitor C13 tracks the capacitor voltage with a slow rise and fast decay characteristic, seeking the lowest continuous background level. The threshold voltage appearing on capacitor C13 is buffered by unit gain field effect transistor input operational amplifier 227.

The output of operational amplifier 227 becomes a signal representing room noise.

As shown in FIG. 10, the 6 dB attenuation circuit 87
The conductor 229 is composed of resistors R24 and R25 which generate a signal on the conductor 229 which is an attenuation of the input signal appearing on the conductor 23 by 6 dB. A comparator 89 formed from an open collector output I, M339 receives at its inverting input the buffering output of the threshold voltage and at its inverting input the 6 dB attenuated signal. Resistor 126 provides switching stability with little hysteresis for comparator 89; therefore, the output of comparator 89 can potentially A logic high level signal is generated on conductor 98 indicating that the signal is being read. conductor 98
The above voltage level also depends on the decision circuit 97 (FIG. 6) K, which will be described below with reference to FIG.

Therefore, referring to FIG. 11, the 6 dB attenuation circuit 93 turns off the oFIliiT switch 235, which is composed of resistors R2B and R29, which applies to the conductor 233 a signal that is attenuated by 6 dB from the input signal appearing on the conductor 223. A field effect transistor switch 235 (P-channel, VpZ3V) is connected between resistor R29 and ground to effectively eliminate the K 6 dB attenuation when switching. Field effect transistor or FET 2
Switching off R29 effectively removes resistor R29 from the circuit.

The signal appearing on conductor 95 switches off FET switch 235 via diode D6.

A resistor 1 is connected between the ground and the cathode of the diode D6.
30 are connected, and the conductor 95 is connected via a ground capacitor C14. Resistor R30 and diode FD6 serve to provide the appropriate control voltage to the gate K of FET 235. Capacitor (i
4 serves to slightly slow the voltage transitions on conductor 95 to minimize noise spikes that are capacitively coupled to the 6 dB attenuation circuit 93 and other circuit portions that can be defeated.

The determination circuit 97 includes an operational amplifier 237 having an inverting input connected to receive the output of the attenuation circuit 93 via a conductor 233. is connected to the MAX bus line via. The resistor R32 is a low value resistor that contributes to the stability of the circuit.When the non-inverting input of the zero-addition amplifier 237 becomes higher than the amplitude of the Wα bus, the diode-PI)7 is in the forward direction. Biased to hold the MAXi line at a level equal to the non-inverting input level. If the non-inverting input of operational amplifier 237 is lower than the voltage on the MAX bus, diode DI will be reverse biased.
Diode DB serves to prevent excessive negative voltage fluctuations from occurring at the output of operational amplifier 237. The bias state of diode D7 is determined by comparator 237 (I, M339)
The comparator is potentially monitored by diode D7
produces a logic high level signal at its output connected to conductor 98 only when it is forward biased. Resistor R33 provides hysteresis to stabilize comparator 239. Resistors R34 and R35 are connected as shown. At least one resistor R36 should be provided to load the Wα bus level holding diode rD7 under all conditions and to enable reliable forward bias sensing by the comparator 239. It is.

The output terminal of comparator 89 (FIG. 10) is connected to conductor 9B (FIG. 11). Comparator 89 and comparator 239 thus participate in their Ausin collector configuration and are connected to the AND circuit (sixth
(symbolically indicated by reference numeral 91 in the figure).

Therefore, the retriggerable one-shot circuit 99 will be activated only when the noise adaptive threshold criterion and the MAX busbar criterion are satisfied. A comparator (LM339) with an open collector output is connected to the circuit R37-141. Comparator 241
serves to discharge capacitor C15 in response to a logic high input signal at its inverting input. Resistor, device R42-R
The comparator 243 (LM339) connected to 47 is
The voltage across capacitor C15 is stored and produces a logic output on conductor 95. Capacitor C15, comparator 243
and associated circuitry provide a hold time of 0.4 seconds for the output signal appearing on conductor 95. This 0.4 second time closes the cap between triggers as described above. When the trigger operation stops, the capacitor C15
It takes 0.4 seconds before 15 reaches sufficient voltage to generate the output of comparator 243 and begins charging again. If the trigger occurs again before 0.4 seconds have elapsed, capacitor C15 is discharged again and the signal on conductor 95 remains unchanged.0 The output signal of retriggerable one-shot circuit 99 appearing on conductor 95 is As shown in FIG. 1.2, it is supplied to the onotic cazola drive circuit 101. Drive circuit 1
01 is used to provide a controlled response and decay time to resistance changes of the Onochical Cazola LJD248 and therefore also of the photoresistor R6 (FIG. 7). This drive circuit consists of an operational amplifier 24 connected as shown.
7.249, diode D9, Dlo, capacitor c1
6-018 and resistors R48-R55. With this circuit configuration, the acoustic signal is gated with a response time of 4 milliseconds and a decay time of 0.3 seconds, producing a streaky signal without clicks. A switching operation that does not occur is realized.

A mute circuit consisting of resistor R69 and transistor Q113 is connected to gate operation control circuit 85.87.8.
9.93.97.99 (FIG. 6), it acts to block the microwave dart signal. The collector and terminal of transistor Q113 are connected in parallel to the input to the IJD drive circuit 101 and the ground terminal which shorts the core input to ground during muting.Resistor R48 connects the short circuit signal to the other gate control circuits. Appropriate logic circuitry (not shown) could now be used to apply a positive voltage to the 0 conductor 75 isolated from the Q113, thereby turning on Q113 and activating muting. According to this type of muting, the dead zone as described above is realized. Referring to FIG. 13, the speaker prohibition signal generator 57 (
FIG. 6) samples the loudspeaker drive signal on conductor 58.

The inhibit signal generator generates a speaker inhibit signal on its output conductor 105. Generator 57 supplies DC to conductor 105.
It functions to frequency equalize 1, rectify 1 and filter the loudspeaker drive signal to generate an output signal. The DC output signal represents the amplitude level of speech or voice from the loudspeaker. Frequency equalization and filtering parameters are determined by a substantially similar circuit 83
It is the same as that of , except that the gain is suitably calibrated to suit the purpose. The inhibit signal generator 103 includes operational amplifiers 251.253.255 connected as shown.
．． 257, diode D11-Dl 4, capacitor c
19-c24 and resistors R56-R65.

Referring again to FIG. 10, the speaker inhibit signal appearing on conductor 105 (from FIG. 13) is applied to operational amplifier 259 to change the threshold voltage level appearing on capacitor C13.
When the voltage level of the 0 conductor 105 supplied to the non-inverting input terminal of
Operational amplifier 259 and related circuit elements are NAT circuit 8
Diode D14 prevents excessive negative voltage fluctuations at the output of operational amplifier 259. If this diode were not present, excessive negative voltage fluctuations as described above would occur across capacitor C13. The feedback of the positive voltage of 0 to the inverting input of the operational amplifier 259 through the buffer operational amplifier 227 and the resistor R67 will result in 0 conductor 105f) N pressure and a voltage of
3, the operational amplifier 259 connects the capacitor C through diode D15 and resistor R6B.
13 to maintain the two voltages at equal levels.

The output signal of operational amplifier 259 is also connected to diode-ISD1
6 to the non-inverting input of the operational amplifier 225, so that the speaker inhibit signal is connected to the capacitor C13.
While controlling the voltage of KL, which would otherwise be present, the input voltage is nullified to prevent conflicting voltage levels across capacitor C13. An immediate positive change in the voltage on capacitor C13, such as caused by a speaker inhibit signal, typically
Operational amplifier 255 pulls in in the opposite direction through diode D5. This problem is avoided by applying the inhibit signal to the non-inverting input of operational amplifier 225 at a slightly higher voltage level than at capacitor C13. This small voltage difference is ensured by the high voltage level at resistor R66 and diode D15 relative to diode D16.

As the speaker inhibit signal on conductor 105 decreases from its peak level, capacitor C13 is connected to diode rD5.
operational amplifier 225 and diode) FD1 via
The discharge is performed in stages under the control of an operational amplifier 259 via 6.

Voltage of capacitor C13 and buffer amplifier 227
The output of the speaker inhibit signal on conductor 105 increases the voltage level and rapid response time of the speaker inhibit signal on conductor 105 until it falls below the microphone level on conductor 223 where normal NA'I' operation is lost. and accurately track decay time.

Once normal NA'r operation is restored, the microphone signal will often represent reverberant attenuation of the loudspeaker sound. The voltage on capacitor C13 then follows this microphone signal as desired.The following examples illustrate the values of the circuit elements.

Resistor resistance value R2, R46B
, 2K R39, 1K R4, R27200 R5470K R75, I K H2, R1111K H31, R67, R50, R51, R52, R4810
0KH12, R55, R4030K H13, R562, 7K R14, R571K H15, R16, R20, R22, R47, R58, R
5951KH17, R18, R60, R61510R1
9, R21$R32, R66, R62, R64100R
24, R25, R45, R6910KR23tR442
, 2M R26, R49, R421, 5M R2B, R29, R34, R35, R6820KH30
, R33, R361M R371R3815K H391,5K R41750 R4327K R53680 R54390 C2,33 C5, C134,7 c7. c9. c10tcl! Lc21+c22
．． 15C8,C20,068 C111c12. C151C17,22CI4
．． 01C16
, ICl3.
047c23. C24,47 microphones could be used housed in separate enclosure elements, and directional patterns other than unidirectional could also be used.

The control circuit of the relevant patent application or, if appropriate, the only one
With two microphones and other types of control circuitry, the system could be configured as a car horn (simple teleconferencing system). The advantages of the outstanding cell gate functions disclosed here are:
It could be maintained even if input audio is present.

Referring again to FIG. 6, the disableable attenuation circuit 93, the determination circuit 97, the AND circuit 91, and the MAX bus 56 are
It would not be needed in a simple microphone teleconferencing system.

Similarly, multiple microphone pickups could be used without a teleconferencing loudspeaker. Referring to FIGS. 5 and 10, it goes without saying that in that case, the power amplifier 59, the inhibit signal generator 57, and the loudspeaker 29 are not required. In addition, an operational amplifier 259,
Diodes Di4, D15, D16 and resistor R6
6. R67% R88 is also not needed and 168 could be turned into a connection.

Also, referring again to FIG. 11, the gate logic signal on conductor 95, for example, may control other related functions such as muting the overhead loudspeaker, automatic video camera switching, or speaker indicator lamps. It could be used in many ways. An output port 94 is provided for extracting logic signals. It would be possible to set a precise micro-contact coverage area or range without the need for weights.

As another variation, directional microphones could be used in an array spaced very closely together.

Typical examples would be an array of two, six or four omnidirectional (cardioid) microphones operating at the same gain, equiangularly spaced and outwardly facing in the same plane. In this case, α mother l1i for each sound source is
I-v (I-determination is primarily based on the relative microphone amplitude rather than the relative arrival time of the voice.

The directivity pattern in the horizontal plane for the case of an array of three omnidirectional microphones is shown in polar coordinate form in FIG. Graphs 401, 403 and 405 show the linear distance from center point 411 for a sound source coming from any angle around the array or array.
The relative sensitivity of the two microphones is 1k (not +IB (at a linear pace)).

Graph 407 represents the directivity pattern of the combination or sum of graphs 401 and 403.

Similar graphs would be obtained for other two-pair combinations. The relative sensitivities of graph 407 are calibrated to have the same overall sensitivity tm as a single cardioid microphone to background room noise and reverberations coming from all directions alike. This directional pattern may be referred to as wide-angle cardioid.

Graph 409 represents the sum of graphs 401, 403 and 405 calibrated to maintain the same sensitivity to room noise and reverberation. This directional pattern is omnidirectional. In symmetrical two or four microphone arrays, opposing pairs of combination cardioids or all combination microphones also form an omnidirectional pattern.

4 microphone arrays or play smells [are 2
Combinations of one or three adjacent microphones form different wide-angle cardioid patterns.

The various directional patterns and surrounds described above are self-evident, even when varying numbers of speakers converse in varying combinations at different locations surrounding the play or arrangement.
It can be obtained using method e-) of the present invention. One or more within the play to obtain a direction-sensitive gating function similar to that disclosed in U.S. Pat. No. 4,489,442 to Andern et al., relatively undisturbed by near reflections and echoes microphones can be muted.

Generally, in automatic microphone gating systems, it is desirable to constantly pick up room noise and reverberations even if the number of microphones gated on varies by a value greater than zero.

In this way, audible background noises such as "exhaust" and "exhaust" are filtered out, and a constant feedback loop gain is maintained even when the microphone is in the loudspeaker's reverberant field. In a teleconferencing device according to a preferred embodiment of the present invention, the microphones are typically spaced far enough apart to have a random phase relationship in response to room noise and reverberations. To constantly pick up noise and reverberations such as those mentioned above, the gain should be attenuated according to the standard practice:

Attenuation -10jog1ONOM where the attenuation is expressed in dB, where NOM is the number of microphones gated to the on state. NOM is 2
For each doubling, the attenuation increases by 3 decibels.

In closely spaced arrays, the amount of attenuation required will be different. The first for three microphone arrays or plays.
In order to obtain the calibration characteristics shown in Figure 4, the following relative attenuation is required.

One microphone is on O,00dB Two microphones are on -5,12+IB Three microphones are on -8,29 To maintain sound, the following relative attenuations are required: One microphone on 0.00 dB Two opposing microphones on -4,77 dB Two adjacent microphones on -5,44 (In3 two microphones are on
-8,45 (In 4 microphones on
-10,79 (LBReferring again to Figure 7, such attenuation characteristics can be achieved more closely by using gated microphone mixing or a similar mixer bus structure as already used in mixer bus 45. If this bus is terminated with a resistor equal to the sum of the on-state resistance of photoresistor R6 and the resistance of resistor R7 multiplied by 4.0, then the result is The following relative damping characteristics are obtained.

1 mic on 0.0011B 2 mics on -5,11dB 3 mics on
-8,30 (In two microphones on -10
, 63dB In this case, the busbar termination resistor (not shown)
would be 22Ω instead of 5.6Ω.

The microphone array could be used singly or in combination with other spaced apart microphones or microphone arrays.

In such a case, a bus that is terminated with a 22 Ω resistor is connected to a local Calcazola in the array by a buffer that gives output to the system-wide gated microphone mixer bus via another Optical Calcazola. is driven whenever any microphone in the array is gated on. The selective design described above allows for the creation and incorporation into automatic microphone dart systems of essentially automatically variable directional characteristics, automatically variable orientation microphones. It should be noted that this design is not limited to unidirectional (carjoid) microphones, nor is it limited to microphones arranged in the same plane.

It should be understood that the above description is of the preferred embodiments of the invention, and that variations and modifications may be made thereto without departing from the spirit and scope of the invention.

[Brief explanation of drawings]

FIG. 1 is a simplified perspective view of the remote conference system or device used in the present invention, and FIG.
3 is a side view of the microphone/loudspeaker device of FIG. 2; FIG. 4 is a block diagram of the remote conference device of FIG. 1; 5
6 shows a block diagram of the microphone/stalker circuit in the circuit shown in FIG. 4. FIG. 7 to 13 are simplified circuit diagrams of the microphone gate circuit of FIG. 6, and FIG. 14 is a diagram showing a microphone directivity pattern obtained in a modification of the present invention. 11...Microphone/loudspeaker device, 13...-Conference table, 15...Control device, 17...Telephone, 1
9... Telephone line jack, 21.23.25... Microphone, 29... Loudspeaker, 41... Microphone/speaker circuit, 43... Control circuit, 45.47.49.
...Conductor, 50...Gate circuit, 51.53.55.
...Microphone gate circuit, 56...side ■ bus bar, 5T...
・Prohibition signal generator, 58.73...Conductor, 61...
Preamplifier/interface circuit, 61... Ozotic cazola switch, 81... Calibration circuit, 83...
Frequency equalization/rectification circuit, 85... Noise adaptive threshold circuit, 8T... Attenuation circuit, 89... Voltage comparator, 91.
...AND gate, 93...6 +IB attenuation circuit, 9
4...output capo), 95.98...conductor, 97...
・Judgment circuit, 99...One-shot circuit, 101...
・Onotic coupler drive circuit, 105...Conductor, 20
3... Field effect transistor-in-dance converter, 2
07.215.217.21B, 221.225.22
7,237.247.249.251.253.255
．． 257.259... operational amplifier, 213.223.
229.1003...Conductor, 239.241.243
...Comparator, 248...Ozoticarcazola LgDs
321... Output amplifier, 334... Mixer/limiter stage, 353... Interface/gate circuit, Q1
02, Q113...Transistor, C...Con procedural amendment (voluntary) May z, 1985

Claims (1)

[Scope of Claims] 1. A plurality of microphones each for generating an electric microphone signal carrying audio information in response to sound; gating means for gating the microphone to the on state, the gating means comprising a reference level for the microphone gated to the on state and an associated microphone signal; comprising monitoring means for continuously monitoring a maximum value of the signal amplitude of said microphone signal at different scaled levels for the associated microphone signal, said monitoring means generating a MAX signal representative of said maximum value; , the monitoring means compares each of the microphone signals to the MAX signal and responsively generates a trigger signal associated with the one microphone for gating the associated microphone in an on state; the gating means includes gating signal generating means for generating a gating signal having at least a predetermined non-zero minimum duration for gating on-state a microphone associated with the trigger signal in response to the trigger signal; , gating means for gating an associated microphone into an on state in response to the gating signal. 2. loudspeaker means for generating sound driven by a loudspeaker signal in the area of said microphone; said gating means for inhibiting gating of said microphone in response to sound from said loudspeaker means; 2. A microphone arrangement as claimed in claim 1, further comprising inhibit signal generator means for generating an electrical inhibit signal associated with the loudspeaker signal. 3. The monitoring means further comprises threshold means for providing a threshold value, the monitoring means comparing the amplitude of each microphone signal with the threshold value, and determining that the microphone signal has a predetermined relationship with the threshold value. 2. The microphone device according to claim 1, wherein the microphone device generates a trigger signal when a predetermined relationship with the MAX signal and the MAX signal is reached. 4. A microphone device according to claim 3, wherein the threshold means comprises means for generating a threshold signal level representative of room noise. 5. The monitoring means further comprises threshold means for generating a plurality of threshold signal levels, each of which is representative of room noise, each of said plurality of threshold signal levels being responsive to a microphone signal generated by the microphone. Responsively, the monitoring means compares the amplitude of each of the microphone signals with the threshold signal, and when the microphone signal reaches a predetermined relationship with the threshold signal and a predetermined relationship with the MAX signal. A microphone device according to claim 1, which generates a trigger signal. 6. The monitoring means comprises threshold means for generating a threshold value, the monitoring means comparing the amplitude of each microphone signal with said threshold value;
and generating a trigger signal when the microphone signal reaches a predetermined relationship with the threshold and a predetermined relationship with the MAX signal, and the threshold means includes means for adjusting the threshold in response to the inhibit signal. A microphone device according to claim 2, comprising: a microphone device according to claim 2; 7. The monitoring means further comprises threshold means for generating a plurality of threshold signal levels, each of which is representative of room noise;
Each of the plurality of threshold signal levels is generated in response to a microphone signal generated by a microphone, and the monitoring means compares the amplitude of each of the microphone signals to the threshold signal, and the monitoring means compares the amplitude of each of the microphone signals to the threshold signal, and the monitoring means compares the amplitude of each of the microphone signals to the threshold signal. a trigger signal is generated when a predetermined relationship is reached with a MAX signal, and the threshold means includes means for adjusting the threshold signal level in response to an inhibit signal. A microphone device according to claim 2. 8. The microphone device according to claim 4, wherein the threshold means receives the microphone signal and responds to its amplitude to generate a threshold signal level with a slow rise and a quick fall. 9. The microphone apparatus of claim 2, wherein each of the plurality of microphones is held in a fixed relationship with each other, and the loudspeaker is held in a fixed relationship with respect to the microphone. 10. A patent in which the microphones are arranged to face outward from a point and are equally spaced apart around a circle centered on the point, and the loudspeakers are arranged to face upward from the point. A microphone device according to claim 9. 11. The microphone device according to claim 1, further comprising output port means for generating a gate signal as an output signal. 12. Claim 1, wherein the gate signal generating means comprises mute control means for mutating the gated microphone into an on state in response to an electrical signal.
Microphone device as described in section. 13. The microphone device according to claim 2, comprising a plurality of loudspeakers connected in a chain. 14. Automatically adjusting the gain of the on-gated microphones according to the number of on-gated microphones to maintain constant the total reverberation field received by the on-gated microphones. 2. The microphone device according to claim 1, further comprising gain adjustment means, and wherein the microphones are widely spaced apart. 15. adjusting the gain of the on-gated microphones according to the number of on-gated microphones to maintain constant the total reverberation field received by the on-gated microphones; 2. A microphone device according to claim 1, comprising automatic gain adjustment means, and wherein said microphones are closely spaced. 16. a plurality of microphones, each of which generates an electrical microphone signal carrying audio information in response to audio; and a plurality of microphones each receiving said microphone signal and responsive to a gate signal, said microphone signal gates an associated microphone in an on state; gating means for generating a threshold signal level representative of room noise; and comparing means for comparing the amplitude of each of the microphone signals with the threshold; loudspeaker means for generating a gate signal when a predetermined relationship is reached and for generating sound in the area of the microphone driven by a loudspeaker signal; and in response to sound from the loudspeaker means. inhibit signal generating means for generating an electrical inhibit signal associated with the loudspeaker signal for inhibiting the gating means from gating the microphone, the inhibit signal being coupled to a direct loudspeaker sound. a microphone device that modifies the threshold signal level to inhibit gating the microphone to an on state, the threshold signal level tracking the microphone level to inhibit gating the microphone to a loudspeaker reverberant sound; . 17. A microphone for generating an electrical microphone signal conveying audio information in response to audio, and gating means for receiving the microphone signal and gating an associated microphone in an on state in response to a gating signal with the microphone signal; threshold means for generating a threshold signal level representative of room noise; comparison means for comparing the amplitude of each of said microphone signals with said threshold; and said gating means for determining that said microphone signal is in a predetermined relationship with said threshold signal level. loudspeaker means for generating a gate signal in the area of the microphone when the signal reaches the microphone; and loudspeaker means for generating sound in the area of the microphone when driven by the loudspeaker signal; inhibit signal generating means for generating an electrical inhibit signal associated with said loudspeaker signal for inhibiting gating of the microphone, said inhibit signal being responsive to the on state of the microphone in response to direct loudspeaker sound. a microphone device that changes the threshold signal level to inhibit gating to loudspeaker reverberation, the threshold signal level tracking the microphone level to inhibit gating of the microphone to loudspeaker reverberation; 18, a noise adaptive threshold circuit comprising: (i) means for generating an amplitude signal representative of the amplitude of the microphone input signal; and (ii) for storing charge to generate a threshold voltage level. (iii) amplifier means for charging said capacitive means in response to said amplitude signal; and (iv) feedback of said threshold voltage to said amplifier means for controlling charging of said capacitive means. (v) a stage for generating a signal representative of loudspeaker sound, the signal generating means applying the signal to the inputs of the capacitive means and the amplifier means. 19. (i) means for generating an amplitude signal representative of the amplitude of a microphone input signal; (ii) capacitive means for storing charge to generate a threshold voltage level; (iv) discharging means for discharging said capacitive means at a rate substantially equal to the rate of decline of said amplitude signal; (v) said amplitude signal; A noise adaptive threshold circuit comprising: scaler means for generating a scaled signal; and (vi) comparison means for comparing said threshold voltage level with a scaled signal of said amplitude signal.