WO1996036109A1 - Systeme reparti de haut-parleurs maitres-esclaves autoregles - Google Patents

Systeme reparti de haut-parleurs maitres-esclaves autoregles Download PDF

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Publication number
WO1996036109A1
WO1996036109A1 PCT/US1996/006187 US9606187W WO9636109A1 WO 1996036109 A1 WO1996036109 A1 WO 1996036109A1 US 9606187 W US9606187 W US 9606187W WO 9636109 A1 WO9636109 A1 WO 9636109A1
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WO
WIPO (PCT)
Prior art keywords
signal
loudspeaker
noise
master
circuitry
Prior art date
Application number
PCT/US1996/006187
Other languages
English (en)
Inventor
Harry L. Davis
Thomas R. Horrall
Original Assignee
Bbn Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bbn Corporation filed Critical Bbn Corporation
Priority to AU58525/96A priority Critical patent/AU5852596A/en
Publication of WO1996036109A1 publication Critical patent/WO1996036109A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R27/00—Public address systems
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/32—Automatic control in amplifiers having semiconductor devices the control being dependent upon ambient noise level or sound level
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/002—Damping circuit arrangements for transducers, e.g. motional feedback circuits

Definitions

  • the present invention relates to audio loudspeaker systems, and more particularly to a system which distributes a common audio signal (message) from one or more inputs to a plurality of locations subject to differing ambient noise.
  • Audio loudspeaker systems are implemented in various environments which affect the intelligibility of the signal output, and the overall efficacy of the communication system.
  • audio paging systems may be implemented in environments, such as a shipboard paging system implemented on a submarine or a public address system implemented in a stadium, wherein background noise varies both spatially and temporally as operating conditions change, e.g. mechanical equipment is cycled on and off, or crowd noise escalates and subsides.
  • the undesirable background noise serves to mask amplified speech to a dramatic extent. Speech that is perfectly intelligible in a given location may be rendered completely unintelligible a few moments later when background noise levels increase.
  • Increasing audio levels system wide to compensate and maintain intelligibility during noisier periods in particular places, may result in system output being uncomfortably or unacceptably loud in other areas where background noise is invariant.
  • Some systems for adjusting the output level of loudspeakers in an audio paging system typically involve manual adjustment of loudspeakers on an individual basis. Such manually-adjusted loudspeakers generally remain at a fixed volume level regardless of varying ambient noise levels near each loudspeaker. Loudspeaker output levels are set and will change only when and if they are manually reset. Manually resetting the loudspeaker output levels to compensate for noise at a particular location during a particular time period usually results in the output levels being too great at other times when ambient noise levels are lesser.
  • loudspeaker output levels may be set unacceptably high so as to be uncomfortably loud during some announcements when ambient noise levels are relatively low, or loudspeaker output levels may be set too low rendering loudspeaker messages unintelligible during time periods when ambient noise levels are relatively high. Otherwise, frequent manual readjustment of the various speakers in numerous locations, or at some central location, must be undertaken to optimize outputs to accommodate temporal and spatial ambient noise level changes.
  • Some automated systems such as one disclosed in U.S. Patent No. 3,410,958 to Cohen, are known to include a system-wide automatic output adjustment mechanism. Accordingly, the loudspeakers in the system operate in conjunction with a centrally located large power amplifier(s) serving a multiplicity of similar loudspeakers distributed among remote locations.
  • a centrally located processor or circuitry near the centrally located power amplifier(s) to adjust gain, and a remote sensor in the area of loudspeaker coverage to send a signal to the centrally located gain circuitry to simultaneously control the level of all loudspeakers connected to the respective power amplifier(s) .
  • the present invention provides a distributed self- adjusting loudspeaker system wherein each master speaker includes self-contained circuitry which senses nearby ambient noise and automatically adjusts the amplified output level of a common input signal to compensate in order to make the announcement audible or intelligible.
  • the system distributes a common audio signal (message) to a plurality of locations subject to differing ambient noise levels and comprises a plurality of master loudspeaker units each associated with a respective location or local area of coverage.
  • Each of the units includes at least one loudspeaker and a microphone for sensing noise at the respective location.
  • the system includes one or more signal inputs and may include signal compression, amplification and conditioning circuitry responsive to all of the signal inputs for supplying a common input signal to each of the distributed master units.
  • Each of the master units includes means, responsive to the respective noise sensing microphone, for adjusting relative gain applied to the common input signal to a respective value corresponding to the local noise level and for applying the gain adjusted signal to the respective loudspeaker.
  • Each master unit incorporates circuitry to produce announcements with a fixed speech (or other input) to acoustic noise ratio over a wide range of noise levels, and a sensing microphone to sense ambient noise in proximity to the master loudspeaker.
  • the sensing microphone works in conjunction with distributed noise controlled amplifier circuitry having automatic gain control to individually adjust each local loudspeaker's output volume as local ambient noise levels change.
  • An associated compressor/equalizer may be included to provide constant voltage control circuitry to adjust the audio signal input to the system to provide a uniform input level independent of its source level.
  • the compressor/equalizer includes a gain control feature that allows the dynamic range of the system to be optimized to compensate for varying input source characteristics.
  • Equalizer circuitry shapes the frequency spectrum of the input signal, to optimize system fidelity or clarity in accordance with important intelligibility or other frequency bands.
  • Individual loudspeaker outputs are automatically adjusted for the ambient noise levels in their immediate vicinity to optimize output of the common signal input signal for maximum intelligibility or clarity, regardless of differences in ambient noise levels at various respective locations.
  • the common input signal is equalized by signal shaping and processing for accurate reproduction to provide maximum talker recognition and optimal signal intelligibility or to otherwise compensate for effects of background noise on the perception of the signal.
  • the noise sensing and level adjusting circuitry in the loudspeaker unit is powered by simplexing dc power onto audio lines to effect the use of common lines to simultaneously transmit ac audio signals and dc power.
  • a primary feature of this alternative embodiment is that existing sound systems can be retrofitted with distributed automatic level adjustment capability, according to the invention.
  • Fig. 1 is a diagrammatic illustration of a system having distributed automatic level control according to the invention
  • Fig. 2 is a block diagram of noise control amplifier and control circuitry for a system having distributed automatic level control according to the invention
  • Fig. 3 is a block diagram of a system having distributed automatic level control according to the invention.
  • Fig. 4 is a diagrammatic representation of automatic level control implemented in a constant voltage (typically 70 volt) announcing system known in the art.
  • a system for distributing a common input signal to a plurality of locations subject to differing ambient noise levels is generally illustrated in Fig. 1.
  • the system involves an unconditioned input signal, or common signal input signal, which may be a voice broadcast signal, background music, or the like.
  • Compressor 10 and equalizer circuitry 12 receive the unconditioned, common signal input signal to provide optimization.
  • the optimized signal is passed to noise controlled amplification circuitry 14 located at a master speaker 16, which also receives a signal indicative of ambient noise from a sensor microphone 18 located proximate to the master speaker 16.
  • the optimized common signal input signal is then adjusted in accordance with the signal indicative of ambient noise, to produce a volume corrected, amplified signal or output signal broadcast from the master loudspeaker 16 and any associated slave loudspeaker(s) 20.
  • the primary purpose of the signal compressor is to keep unconditioned, common signal input signal to the system constant in level.
  • Other circuitry described hereinafter changes signal level by varying gain at loudspeakers as required to compensate for the local effects of variable ambient noise, but the common signal into the system must be maintained constant to assure that the final speech-to-noise ratio desired is achieved.
  • the initial conditioning effected by the compressor (in conjunction with the equalization discussed hereinafter) contributes to the accurate reproduction of the input signal and to enhanced talker recognition.
  • the compressor 10 provides constant voltage control to the input signal that compensates for signal variations, for example, in the sound pressure level at an input signal microphone diaphragm due to different talker effort and level, and due to variable microphone-to-talker distance.
  • the latter effect can cause dramatically different microphone output levels with conventional microphones, and is exacerbated when noise-cancelling differential type microphones are used.
  • the signal compressor 10 operates by electronically monitoring its output level and automatically adjusting its gain as required to keep the level constant. If a talker speaks loud or holds the microphone close, the signal output from the compressor would tend to rise. However, the rise is kept to a fraction of a decibel, in accordance with a selectable gain as discussed hereinafter, because a high gain negative feedback control circuit quickly serves to reduce the overall gain of the compressor 10. If a talker speaks with low effort or holds the microphone further away, the compressor compensates by increasing its gain accordingly.
  • the signal compressor 10 may include a user- accessible switch 22 (Fig. 1) for changing the reference output, after compression, to the levels desired for various modes of operation. For instance, it may be desirable to be able to manually switch the compressor 10 to achieve selected gains for emergency (loud) announcements, normal announcements, and/or quiet announcements. Exemplary nominal compressed output voltages from the compressor implemented with selectable gains are 1 Vrms (0 dB) in an emergency mode, 1/2 volt (- 6 dB) in a normal mode, and 1/4 volt (-9 dB) in a quiet mode.
  • a second, non-user-accessible switch (not shown) , may be provided to adjust the amount of gain to optimize use of the system in different environments or with different equipment.
  • the equalizer 12 is intended to adjust the overall frequency response of the system as required for optimum balance between intelligibility, naturalness and signal power.
  • adjustments are provided for speech frequencies from 315 Hz to 5000 Hz in 1/3 octave bandwidths.
  • the range of adjustability for each band level is 24 dB.
  • the adjustment is accomplished by installing semi-permanent resistors soldered to a removable plug-in component carrier in the equalization circuitry of the illustrative embodiment.
  • the level of each band is established by a single resistor in the range of 0-500,000 ohms.
  • a plug-in potentiometer test panel permits convenient band level adjustability during initial system setup.
  • the equalizer 12 includes a calibrated precision stepped attenuator which permits gain adjustment with 1 decibel resolution over a range of 59 dB.
  • the compressed/equalized signal is passed to a noise control amplifier (NCA) 14, as illustrated in Fig. 2, for correction in accordance with ambient noise levels sensed proximate to the loudspeaker(s) .
  • NCA noise control amplifier
  • the NCA circuitry is intended to be installed within an amplifier unit resident in the master loudspeaker 16 enclosure, as a representative embodiment.
  • the NCA is comprised of two main elements.
  • the first NCA element is an ambient-noise sensing sound level meter, or SLM 24.
  • the SLM 24 receives a signal representing ambient noise sensed with a dynamic omnidirectional sensing microphone 18.
  • the noise signal in this illustrative public address system embodiment, is filtered by a 1-4 kHz octave band filter 26 so that the SLM output is sensitive in the frequency bands which contribute most to speech intelligibility.
  • the filtered noise signal is rectified 28 so that the SLM output is a rectified DC control voltage proportional to the sound pressure level in the 1-4 kHz octave bands. At very low ambient noise levels or when DC power appears at the control input indicating activation of the announcing system, the DC output voltage is held constant.
  • SLM control circuitry in the form of a hold switch 30 and a hold capacitor 32 continuously sense the DC control voltage, as long as the switch 30 is in the closed position. With the switch 30 closed, the hold capacitor maintains a charge, or control voltage, that is proportional to the ambient noise level sensed by the sensing microphone 18. The charge changes according to the change in ambient noise levels while the switch 30 is closed.
  • the hold capacitor 32 Upon opening of the switch, such as upon commencement of an announcement or delivery of the common signal input signal, the hold capacitor 32 contains a charge representative of the ambient noise level immediately prior thereto.
  • the second main NCA element is a variable gain audio amplifier or voltage-controlled-amplifier (VCA) 34.
  • VCA 34 accepts the fixed level, compressed signal from the compressor/equalizer at a VCA audio input.
  • the VCA applies ambient noise controlled gain to the fixed level, compressed signal.
  • Gain is applied proportional in decibels to the DC voltage supplied to a VCA control input by the hold capacitor 32 of the SLM 24. During an announcement the gain is kept constant because the SLM DC output is held constant due to the fact that the hold switch 30 is open and the charge on the hold capacitor 32 is fixed at the level it was when the switch 30 was opened. At very low levels of ambient noise the gain is also constant.
  • the NCA audio output in the form of a signal that has been compressed, equalized and amplified or adjusted in accordance with the ambient noise signal, is fed to other components resident at the master loudspeaker.
  • the NCA output signal is fed as input to a 20 watt audio power amplifier 36 resident in the loudspeaker enclosure.
  • One general concept employed for the master loudspeaker enclosure layout is to include virtually all of the system electronics, except for the compressor/equalizer circuitry, so as to provide a self contained unit.
  • the NCA 24 and the 20 watt power amplifier 36 are incorporated into the master loudspeaker enclosure along with a matching auto-transformer 38, and a loudspeaker transducer 40.
  • the autotransformer 38 provides impedance matching between the 20 watt amplifier 36 and the loudspeaker transducer 40, and is intended for mounting with each loudspeaker transducer in the system whether used as a master or slave.
  • master loudspeakers include a resident 20 watt power amp, so the purpose of the autotransformer is to match the total loudspeaker load impedance seen by the master power amplifier for optimum power output and freedom from overload.
  • Up to four slave loudspeaker units can be operated from the master, in this illustrative embodiment, each of which includes a transducer and autotransformer only.
  • a second important function of the autotransformer 38 is to permit adjustment of output power from each loudspeaker to the desired level. Power taps are provided in 3 decibel steps over a range of 15 decibels.
  • the autotransformer is a single-winding tapped transformer. The advantages that accrue to use of a single-winding tapped transformer, compared to a dual winding transformer, include less insertion loss (internal power losses) and a more compact size.
  • the loudspeaker 40 is a directional re-entrant type exponential flare horn loaded reproducer, with a single voice coil and compression loaded driver (not multi-way) .
  • the choice of transducer is primarily a function of the particular application and the dimensional requirements of the enclosure. The same transducer type may be used for both master and slave assemblies.
  • the concept of simplexing is implemented, integrating alternating current and direct current for transmission over a single wire pair. Accordingly, appropriate simplexing circuitry is effected to transmit to the master loudspeaker enclosure both the input audio signal and the d.c. power required to drive the NCA and associated loudspeaker level adjustment circuitry.
  • the NCA would include circuitry required to decouple the a.c. and d.c. signals.
  • Such an implementation permits retrofitting of the distributed automatic level adjustment capability according to the invention into existing 70.7 volt or other constant voltage-type announcing systems.
  • Fig. 4 the concepts of the technology described hereinbefore are applicable to 70 volt announcing systems presently used in commercial industry.
  • Technology can be implemented or retrofitted into current 70 Volt loudspeakers as either internal modifications (i.e., circuit card, microphone, power source) , or as an external module containing the required elements which could be located adjacent to each loudspeaker.
  • the important design characteristics of the automatic level control circuit are the total adjustment range required and the resolution of the level control.
  • the adjustment range is set by the maximum variability of ambient noise at the locations of the loudspeakers.
  • the audio level resolution is set by acceptable variation in signal loudness or intelligibility.
  • a typical 70 volt system such as known in the art may require a 40 dB adjustment range with a maximum of 3 db control increments.
  • the circuitry for retrofitting automatic level control consists of a sound level meter circuit, an audio level control technique and a power source.
  • the sound level meter circuit is to measure and process the ambient noise to provide a control signal for the loudspeaker gain control.
  • the Noise Control Amplifier described contains such a circuit which is applicable to the 70 volt system.
  • This circuit consists of a dynamic microphone, a microphone preamplifier circuit, a three octave band filter which filters the ambient noise such that the loudspeaker gain is sensitive in only the 1 kHz to 4 kHz octave bands which are important for speech intelligibility, and a rectifier circuit which produces a DC control voltage proportional to the sensed ambient noise.
  • This circuitry can be readily implemented into any 70 volt design, but would require continuous power.
  • Power can be supplied to the circuitry locally from a 115 VAC source and with the use of a DC power supply.
  • the required DC power 50 can be placed on the audio line 52 at the central amplifier(s) 54, which is part of the existing announcing system, and filtered from the audio signal prior to the loudspeaker. Simplexing techniques can be implemented as discussed hereinbefore, and the DC power used to power both the SLM 65 and the ambient noise sensing microphone 58.
  • the SLM circuitry provides a DC output that is provided, according to logic circuitry 60 which may be required depending upon the implementation, to level control circuitry 62 that attenuates audio power so as to provide the necessary output signal to the loudspeaker 64.
  • the system described hereinbefore with respect to Figs. 1-3 provided variable gain to the audio signal prior to the local 20-watt amplifier contained in each high power loudspeaker.
  • a 70 volt announcing system does not use a distributed amplified announcing implementation.
  • the 70 volt system provides a high power audio signal to each loudspeaker and uses matching transformers to determine the fixed level of each loudspeaker.
  • the 70 volt system requires an alternate level control or power attenuation technique.
  • a power MOSFET circuit in the form of a voltage controlled power MOSFET circuit is placed in series with the 70 volt loudspeaker.
  • the MOSFET circuit provides variable power dissipation controlled by the SLM DC control voltage.
  • Power MOSFETs known in the art can be implemented without elaborate logic circuitry. Power dissipation requirements would be a function of system power considerations.
  • the audio level at the loudspeaker can be controlled by inserting a power resistor network in series with the loudspeaker and using a logic circuit to switch different resistors in or out of the circuit based on the SLM DC control voltage.
  • a power resistor network in series with the loudspeaker and using a logic circuit to switch different resistors in or out of the circuit based on the SLM DC control voltage.
  • full available power would be delivered to the loudspeaker; as the ambient noise decreased, power resistors would be switched into the audio path to dissipate the unwanted audio power.
  • This technique requires several high power resistors and a logic circuit to provide the required switching.
  • MOSFET circuitry or a power resistor network can be implemented, it should be appreciated that other means can be implemented for dissipating or attenuating audio power to effect level control.
  • a multi-tapped matching transformer can be configured to have the desired audio level adjustment range and resolution. Audio level control would be implemented through switching the transformer output taps based on the SLM DC control voltage level.
  • an appropriate ambient noise sensing microphone is a miniature, low impedance, dynamic, omnidirectional pressure sensing microphone. It could be recessed within the loudspeaker amplifier assembly cover. It should be appreciated that the microphone could alternatively be extended to another mounting location should the ambient noise at the amplifier be deemed not representative of noise levels near listeners.
  • the primary performance requirements of the sensing microphone in this illustrative embodiment are smooth frequency response throughout the speech frequencies and stable sensitivity from unit to unit so that the output DC voltage of the SLM is uniquely determined by the ambient noise level.
  • the microphone may be "hardened” to withstand large amounts of shock and vibration, or it may be required that it have a flat frequency response at other frequencies.
  • the signal output from the compressor in the illustrative embodiment discussed herein is passed to an equalizer in which adjustments are provided for speech frequencies from 315 Hz to 5000 Hz in 1/3 octave bandwidths and wherein the range of adjustability for each band level is 24 dB
  • different adjustment bands may be implemented.
  • the desired frequency bandwidth might be 20 Hz to 20000 Hz, or greater, with significantly different bands for adjustment and range(s) of adjustability.
  • output from the sensing microphone is filtered by a 1-4 kHz octave band filter so that the SLM output is sensitive in the frequency band which contributes most to speech intelligibility
  • filter bands can be implemented to tailor the system to the types of ambient noise and audio signals processed.
  • the electronics are described as being included in a self contained loudspeaker enclosure, excluding the compressor/equalizer, portions of the electronics can be implemented outside of the loudspeaker enclosure, and where it is possible to deliver adequate power to the power amplifier and compressor/equalizer circuitry, the compressor equalizer circuitry may be contained in the loudspeaker enclosure as well.
  • the ambient noise sensing and gain control circuitry may be designed to operate either between message input signal intervals or continuously, including during message input signals.
  • the input voltage to the loudspeaker may be compared to the sensing microphone output voltage by a suitable comparator circuit.
  • the audio signal gain would be reduced until a given amount of mismatch occurs, implying a predetermined signal to acoustic noise ratio.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Circuit For Audible Band Transducer (AREA)

Abstract

L'invention se rapporte à un système réparti de haut-parleurs autoréglés, dans lequel chaque unité haut-parleur maître comporte un circuit autonome (14) qui détecte le bruit ambiant près de chaque unité haut-parleur maître (16) juste avant ou pendant une annonce, et règle automatiquement le niveau de sortie amplifié de l'annonce au niveau de chaque haut-parleur maître (16) et de(s) haut-parleur(s) esclave(s) (20) associé(s) afin de compenser les niveaux de bruit ambiant. Le système répartit un signal audio commun entre plusieurs emplacements soumis à différents niveaux de bruit ambiant et comprend une pluralité d'unités (16) haut-parleurs maîtres associées chacune à un emplacement respectif. Chacune de ces unités (16) comprend au moins un haut-parleur et un microphone (18) qui détecte le bruit à l'emplacement respectif. Le système comporte une ou plusieurs entrées de messages ainsi qu'un circuit central unique de préamplification et de conditionnement (10, 12) sensible à l'entrée ou aux entrées de signaux, ce qui permet d'envoyer le signal ou les signaux entrants résultant du signal commun à chacune des unités haut-parleurs maîtres. Chacune de ces unités haut-parleurs maîtres comporte un organe, réagissant au microphone (18) respectif détectant le bruit ambiant, afin de régler le gain relatif appliqué au signal ou aux signaux entrants du message par rapport à une valeur respective correspondant au niveau de bruit local, et d'appliquer au haut-parleur considéré le signal entrant réglé en gain.
PCT/US1996/006187 1995-05-10 1996-05-02 Systeme reparti de haut-parleurs maitres-esclaves autoregles WO1996036109A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU58525/96A AU5852596A (en) 1995-05-10 1996-05-02 Distributed self-adjusting master-slave loudspeaker system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US43830395A 1995-05-10 1995-05-10
US08/438,303 1995-05-10

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Publication Number Publication Date
WO1996036109A1 true WO1996036109A1 (fr) 1996-11-14

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0907281A1 (fr) * 1997-10-03 1999-04-07 Harris Corporation Système d'appel
GB2426169A (en) * 2005-05-09 2006-11-15 Sony Comp Entertainment Europe Controlling the respective volume of each of a plurality of loudspeakers
WO2006066351A3 (fr) * 2004-12-26 2006-12-21 Creative Audio Pty Ltd Systeme de radiomessagerie perfectionne
EP1847154A2 (fr) * 2004-12-02 2007-10-24 Koninklijke Philips Electronics N.V. Detection de position au moyen de haut-parleurs utilises comme microphones
WO2009025705A1 (fr) * 2007-08-16 2009-02-26 Thomson Licensing Processeur audio de réseau
US8619821B2 (en) 2011-03-25 2013-12-31 Invensense, Inc. System, apparatus, and method for time-division multiplexed communication
CN103945316A (zh) * 2014-04-29 2014-07-23 天津市黎明时代轨道交通技术有限公司 一种有源数字线阵列
CN109686024A (zh) * 2017-12-31 2019-04-26 湖南汇博电子科技股份有限公司 火灾逃生播报方法及系统

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US5046101A (en) * 1989-11-14 1991-09-03 Lovejoy Controls Corp. Audio dosage control system
US5434922A (en) * 1993-04-08 1995-07-18 Miller; Thomas E. Method and apparatus for dynamic sound optimization
US5509081A (en) * 1992-10-21 1996-04-16 Nokia Technology Gmbh Sound reproduction system

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US4630302A (en) * 1985-08-02 1986-12-16 Acousis Company Hearing aid method and apparatus
US4868881A (en) * 1987-09-12 1989-09-19 Blaupunkt-Werke Gmbh Method and system of background noise suppression in an audio circuit particularly for car radios
US5046101A (en) * 1989-11-14 1991-09-03 Lovejoy Controls Corp. Audio dosage control system
US5509081A (en) * 1992-10-21 1996-04-16 Nokia Technology Gmbh Sound reproduction system
US5434922A (en) * 1993-04-08 1995-07-18 Miller; Thomas E. Method and apparatus for dynamic sound optimization

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0907281A1 (fr) * 1997-10-03 1999-04-07 Harris Corporation Système d'appel
EP1847154A2 (fr) * 2004-12-02 2007-10-24 Koninklijke Philips Electronics N.V. Detection de position au moyen de haut-parleurs utilises comme microphones
WO2006066351A3 (fr) * 2004-12-26 2006-12-21 Creative Audio Pty Ltd Systeme de radiomessagerie perfectionne
US8599724B2 (en) 2004-12-26 2013-12-03 Creative Audio Pty. Ltd. Paging system
GB2426169A (en) * 2005-05-09 2006-11-15 Sony Comp Entertainment Europe Controlling the respective volume of each of a plurality of loudspeakers
GB2426169B (en) * 2005-05-09 2007-09-26 Sony Comp Entertainment Europe Audio processing
WO2009025705A1 (fr) * 2007-08-16 2009-02-26 Thomson Licensing Processeur audio de réseau
US8755532B2 (en) 2007-08-16 2014-06-17 Thomson Licensing Network audio processor
US8619821B2 (en) 2011-03-25 2013-12-31 Invensense, Inc. System, apparatus, and method for time-division multiplexed communication
CN103945316A (zh) * 2014-04-29 2014-07-23 天津市黎明时代轨道交通技术有限公司 一种有源数字线阵列
CN109686024A (zh) * 2017-12-31 2019-04-26 湖南汇博电子科技股份有限公司 火灾逃生播报方法及系统

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