Abstract: The present invention relates to a drive-in movie theater and/or events center preferably located on top of one or more parking garages located at a shopping mall or other similar complex. The drive-in theater preferably has a short range radio broadcast system that can send radio signals to cars on the parking garage, wherein movie-goers can listen to the movie sound tracks on their own car stereos/radios. When needed, the present system contemplates having more than one transmitter, each operating at a different frequency, so that the effective service range of each transmitter can be made within limited guidelines set by the FCC. The drive-in theater can be combined with an events center and connected to a shopping mall where access to restaurants and retail establishments can be provided.

Abstract: An improved light weight, portable public address system configured with high fidelity omni-directional and high wattage directional speakers for both indoor and outdoor use with a wide variety of sound inputs assembled in a self-contained, compact housing. Optional systems provide for the remote deployment of up to two speakers and the use of a remote wireless microphone. Improved options include a unique compact configuration that allows for modular construction of all components for plug and play operation and rapid field replacement; a weatherproof housing for operation in inclement weather, and a tape player to provide prerecorded programming.

Abstract: An apparatus and method for providing a centralized speaker system that allows multiple speakers connected to a central amplifier speaker line to be monitored and controlled from a central location via a master/slave protocol. The centralized speaker system comprises a central station for selectively communicating at least one of a command and an information signal to a destination device. A tone generator is adapted to communicate an activation tone to the destination device. An amplifier, which is colocated with the central station, is adapted to amplify the signals to the destination device.

Abstract: According to the present disclosure, a digital vehicle microphone system for recording and playback of announcements pertaining to vehicle stops and route information is provided for use over public address systems installed on public transportation vehicles. The system includes a microphone apparatus for digitally pre-recording the announcements. The microphone apparatus includes a microphone, a mute switch, a radio mode switch, a record switch and a record indicator. The system also includes a control circuit for recording and storing at least two separate announcements onto memory storage devices. The control circuit further includes a delayed playback feature for delayed playback of the announcements through the vehicle's public address system. The microphone apparatus further includes a “hands free” microphone including hand and foot actuated recording switches.

Abstract: A full-frequency-range cinema loudspeaker system intended or deployment in limited space behind a perforated cinema screen is configured as three modules: (1) a high-frequency module having a compression driver working into a horn-shaped waveguide that is specially shaped to compensate for beam-spreading effects of the perforated screen, (2) a midrange module providing a specially shaped waveguide with a multiple throat portion that mounts four cone-type drivers in a vertical array, the four individual throat regions merging into a common mouth portion of the waveguide that flares out to the front of the module, and (3) a vented-port low-frequency module with two cone-type low-frequency loudspeaker units. The three modules are stacked with the high-frequency module on top and the low-frequency module at bottom; The modules are all made to have a uniform width and a depth of under eighteen inches.

Abstract: A process for the configuration of a public address system with at least one speaker box (8) and one amplifier (1) including a DSP (2.2) in the audio signal path supplying the speaker box (8) with an audio signal uses data that are transmitted by the speaker box (8) transmitted to the amplifier (1). Using these data, signal processing adapted to sound technology and/or electrical characteristics or surrounding conditions of the speaker box is adapted in the DSP (2.2), possibly in other functional elements of the amplifier (1). The data concern desired signal processing in the amplifier and are structured in a data format not specific to the DSP. They are converted in the amplifier (1) into DSP-specific parameter data. For the data conversion, interpretation data contained in the amplifier (1), which data relate to information concerning the DSP (2.2), possibly to additional functional elements in the amplifier (1), are used.

Abstract: When a person first enters an unfamiliar work space, it is useful for that person to know what devices are present in the space and often the person will spend the first few minutes looking around, effectively carrying out an inventory of the devices present. In order to simplify this process the devices are arranged to announce their existence by sound in response to a prompt, such as a handclap. To avoid the announcements being made all at once in an unintelligible manner, the devices interact with each other to order their announcements so that each device announcement is, at least in due course, made uninterrupted by announcements from other devices. Typically, this interaction involves the devices using a collision-detection and back-offprotocol applied to the announcements themselves.

Abstract: The invention pertains to a method and a device for operation of a public address system with at least one loudspeaker box and with at least one amplifier, which is connected by means of a preferably detachable cable connection and/or by means of a non-cable-based connection, to the loudspeaker box, characterized in that in a first process step, the amplifier receives data pertaining to acoustical and/or electrical parameters of the loudspeaker box by inquiry of the loudspeaker box, and that in a second process step, the amplifier is configured automatically, under consideration of the data/parameters, for operation with the connected loudspeaker box.

Abstract: A sound emiting device for providing at least one new sonic or subsonic frequency as a by-product of emitting a waveform of at least two ultrasonic frequencies whose difference in value corresponds to the desired new sonic or subsonic frequency. The device includes a parametric emitting perimeter positioned around a central open section. This open section is structured with a diagonal width greater than a cross-sectional diagonal of the parametric emitting perimeter. An ultrasonic frequency signal source and sonic/subsonic frequency generator are coupled together to a modulating circuit for mixing an ultrasonic frequency signal with an electrical signal corresponding to the at least one new sonic or subsonic frequency. The modulator output is coupled to the emitting perimeter which comprises ultrasonic frequency emitting material for propagating the mixed waveform into air for demodulating the waveform to generate the at least one new sonic or subsonic frequency.

Abstract: An integrated receiver mixer system is disclosed wherein the plurality of wireless receivers is remotely controlled, and retained in synchronism, via reference and control signals outputted by the system mixer. Further, pairs of receivers are connected to each other, and to the mixer, in a manner which minimizes the requisite cabling therebetween.

Abstract: An addressable speaker system in which a plurality of selectively activated speakers are distributed throughout a predefined area and are connected to a central processing unit. The system contains multiple RF antennas that are capable of broadcasting and receiving radio frequency signals to individuals wearing radio frequency identification (RFID) badges. The system users the RF transmission to locate an intended radio frequency identification badge and selectively broadcasts an audio message to a speaker located closest to the intended recipient.

Abstract: An alarm signaling device (5) operable to produce an alarm signal and, possibly, communicate emergency announcements when triggered by a signal from a central alarm control panel. The alarm includes a speaker or other sound producing device and a silencing circuit (14) that can be engaged by a person in the room to temporarily disable the speaker. The silencing circuit includes a timing circuit (30) and a switch (32) consisting of a pair of touch contacts (38, 40) that are activated by body resistance. The timing circuit (30) is operable to automatically re-enable the speaker after a predetermined time period has been measured. Furthermore, though the speaker has been silenced by the silencing circuitry (14), a reactivation circuit (15) continues to receive and process signals in order to identify a re-enablement signal by its particular frequency and duration.

Abstract: A remote broadcast vehicle does not require any setup time, may remain fully enclosed and locked while in operation, and which prevents the ingress of moisture and other weather. The vehicle may includes a player for pre-recorded audio programs, a radio broadcast station receiver, wireless microphone and wireless remote control, mixer, cross-over, amplifiers and speaker assemblies. The system may further be used to up-link a program to a base radio station, and provide full programming capability. Additionally, a tuned port speaker system is disclosed for broadcasting low frequencies through the vehicle wall. Several different vehicle embodiments are illustrated.

Abstract: The invention relates to a method for implementing a sound reproduction system for a large space, and a sound reproduction system. In accordance with the invention, a) loudspeaker units (LU) are placed in different parts of said space, and the information to be transmitted by the loudspeaker unit to its environment is fed to said loudspeaker unit from an information source (CPU) common to several loudspeaker units, b) determinations specific to said loudspeaker unit are carried out in a separate loudspeaker unit (LU), and c) a message is sent from the loudspeaker unit (LU) to the common information source (CPU), said message (20) containing information obtained on the basis of said determination.

Abstract: A loudspeaker system having a cross-cabinet horizontal array of loudspeakers for collectively generating a common acoustical wavefront when respective drivers associated with each of the loudspeakers of the array are similarly driven. The loudspeakers are secured to each other such that adjoining horn side walls for adjacent ones of the loudspeakers are substantially parallel to each other and are relatively deep in relationship to the total length of the loudspeakers, i.e., the length of the sidewalls is about 80% of the depth of the entire loudspeaker. Each horn is angled about 30 degrees off a central axis thereof to provide 30 degrees coverage in the horizontal plane and includes a first, essentially untapered, section which provides the aforementioned coverage in the horizontal plane and a second section having a taper of about 30% to prevent diffraction of the wavefront at the edges of the horn.

Abstract: A sound delivery system comprises at least one elongated speaker mounting element. A multiplicity of individual speakers are mounted in the mounting element to form a linear array of speakers with each speaker being adapted to radiate sound in a direction transverse to the array. The number of speakers and the spacing between them are selected so as to focus the sound emanated by the speakers by reducing dispersion of sound in the direction of the linear array. A device is also included for coupling audio signals to the speakers.

Abstract: A system for detecting whether a bus used to connect units in an in-flight entertainment system is properly terminated. A detection circuit generates a bus termination signal when a terminating cap properly terminates the bus. Prior to installation of the terminating cap, a bus coupling contact of the detection circuit is maintained in a logic high or asserted state. A detection loop in the terminating cap grounds or deasserts the bus coupling contact when the terminating cap is properly installed. A microcontroller determines whether the bus coupling contact is grounded and signals a managing unit of the condition. The managing unit may display an appropriate error message to notify service personnel of the improper termination.

Abstract: An apparatus compensates for an attenuation of a signal on a telephone line in a communication system connected to the telephone line via a transformer. A photo coupler detects a loop current at a primary winding of the transformer. A controller generates switching control signals corresponding to an output of the photo coupler based on a predetermined switching table, and controls an overall operation of the communication system by receiving coding data. A level amplifier having different gains amplifies a signal at a secondary winding of the transformer by the gain corresponding to the switching control signal. A coder codes an output from the level amplifier to generate the coding data.

Abstract: A sound projection device for use in speaking to one or more specific persons on a selective basis, the device including a housing having a directional aspect for aiming the housing at a target area, a gripping handle coupled to the housing to enable the device to be held in a user's hand, and a parametric speaker coupled to a front end of the housing for indirectly generating at least one new sonic frequency from at least two ultrasonic frequencies of different value. The housing includes a luminating source having a directional orientation substantially aligned with the directional aspect of the housing. The combination of light and directional sound source enables the user to visually identify the target area before transmitting the sonic frequency to the target.

Abstract: An audio enhancement system and method is provided wherein a wireless headphone system comprises a transmitter and a receiver. The transmitter for this system broadcasts a Direct Sequence Spread Spectrum (DSSS) CDMA signal on a number of separate code channels in the 902-928 MHz ISM band. Each successive code channel will have its audio signal delayed by a preset period, e.g. 30 mS, relative to the previous channel. A reference signal on one or more separate time synchronized code channels will be simultaneously transmitted from multiple dedicated transmitters within the venue. Analysis of these multiple code channels by the electronics in the headset will provide the headset with an approximate radial distance from the stage. The headset receiver, supporting position location signals, and associated hardware will select the appropriate audio code depending on the listener's distance from the main loudspeakers.

Abstract: A sound delivery system comprises at least one elongated speaker mounting element. A multiplicity of individual speakers are mounted in the mounting element to form a linear array of speakers with each speaker being adapted to radiate sound in a direction transverse to the array. The number of speakers and the spacing between them are selected so as to focus the sound emanated by the speakers by reducing dispersion of sound in the direction of the linear array. A device is also included for coupling audio signals to the speakers.

Abstract: A four-dimensional acoustical audio system utilizes both spatial and temporal signal processing to provide uniform sound throughout a range of ear levels in an enclosure and combines the output of loudspeakers above and below the desired level to substantially eliminate the perceived direction and location of the sound sources and effectively creates a phantom sound source at the desired level

Abstract: A audio enhancement system and method of use with a sound system for producing primary sound from at least one main loudspeaker located at a main position. The audio enhancement system comprises at least one wireless transmitter, time delay circuitry, and plural augmented sound producing subsystems. Each sound subsystem is a portable unit arranged to be carried by a person located remote from the main loudspeaker and includes a wireless receiver and an associated transduce device, e.g., a pair of stereo headphones. The transmitter broadcasts an electrical signal which is representative of the electrical input signal provided to the main loudspeaker. The broadcast signal is receiver by the receiver and is demodulated and amplified to drive the transducer so that it produces augmented sound substantially in synchronism with the sound arriving from the main loudspeaker.

Abstract: An audio enhancement system and method is provided wherein a wireless headphone system comprises a transmitter and a receiver including a synchronization device which utilizes electromagnetic locating signals to locate the position of the receiver with respect to the transmitter. The transmitter for this system will broadcast a frequency modulated (FM) signal on a number of separate channels in the 900 MHz band range. Each channel will carry the same audio information, however, each successive channel will have its audio signal delayed by a preset time period, e.g. 50 ms, relative to the previous channel. The headset receiver, supporting position location signals, and associated hardware will select the appropriate channel depending on the listener's distance from the main loudspeakers.

Abstract: A sound generation device used in a public space generates tone data corresponding to a change in environment such as environmental noise, temperature, brightness, and the like. The sound generation device includes a detector for detecting environmental noise, temperature, brightness, and the like, and forms tone control data on the basis of the detected environment information. Tone parameters to be supplied to a tone generation LSI or a sound effect DSP are controlled according to the tone control data, thereby selecting and controlling a play No. of tone sources, tone color, tone volume, tempo, reverberation, and the like of tones or music tones to be generated.

Abstract: A transport apparatus for large network telecommunication equipment, includes a central switch frame for holding electronic equipment, and having first and second switch bays and a main controller bay sandwiched between the first and second switch bays in an in-line, rigidly fixed manner; first and second end cable storage frames, each for holding cables; first and second junction panels; a first hinge assembly for hingedly connecting one end of the first junction panel to the first end cable storage frame and an opposite end of the first junction panel to the first switch bay to pivotally move the first end cable storage frame between an in-line configuration in-line with the first switch bay and a folded configuration positioned in front of the first switch bay; a second hinge assembly for hingedly connecting one end of the second junction panel to the second end cable storage frame and an opposite end of the second junction panel to an opposite end of the second switch bay to pivotally move the second end

Abstract: A broadcast system for a facility including audio and video signal generators that may also include the audio output of a microphone for forming broadcast signals. The broadcast signals include a program signal, a supervisory program signal and a supervisory alert signal. The power supply for monitoring stations and broadcast signals are combined to form an output signal that is broadcasted throughout the facility. A bus distributes the output signal in the facility to each of a plurality of monitor stations. Each monitor station includes decoders to recover the audio and video signals and form a resident power supply for that monitor station only from the output signal on the bus. The monitor could also includes a video monitor and speaker coupled to the resident amplifier to the resident power supply for responding to any of the broadcast signals. A resident controller controls the resident amplifier when receiving a program signal supplied to the monitor.

Abstract: An automated display demonstrates a loudspeaker in response to selections by a potential customer. The display permits accessible storage of the demonstrating loudspeakers.

Abstract: Intelligibility of a human voice projected by a loudspeaker in an environment of high ambient noise is enhanced by amplifying formants (26, 28, 30) of the voice. Because intelligibility of the human voice is derived largely from the pattern of frequency distribution of voice formants, selective enhancement of the formants provides much more readily understandable speech in the presence of high background noise with but minimal increase in amplitude of the speech. Formants are processed by individually selecting them in a spectrum analyzer (42, 124) and individually amplifying (50, 58, 74, 80, 140 through 146) and selectively weighting (56, 57, 78, 82) them before recombining processed formants and unprocessed base band voice components (130) to provide an output signal (116) of greatly improved intelligibility.

Abstract: A sound field control device for simulating a sound field of a small space such as a concert hall in a large space such as an open outdoor space and a large indoor space comprises loudspeakers for controlling a sound field disposed at or in the vicinity of positions in a real space corresponding to positions on a hypothetical peripheral plane which defines a hypothetical space in the real space, and a hypothetical reflected sound synthesizing section for synthesizing hypothetical reflected sounds on the basis of the sounds from a real sound source and supplying the synthesized hypothetical reflected sounds to the loudspeakers. The hypothetical reflected sounds are synthesized so that they will simulate sounds which are emanated from the real sound source and reflected from the hypothetical peripheral plane of the hypothetical space. A natural sound field in which one feels as if he was in an indoor concert hall can be obtained in the whole hypothetical space.

Abstract: A audio enhancement system and method of use with a sound system for producing primary sound from at least one main loudspeaker located at a main position. The audio enhancement system comprises at least one wireless transmitter, time delay circuitry, and plural augmented sound producing subsystems. Each sound subsystem is a portable unit arranged to be carried by a person located remote from the main loudspeaker and includes a wireless receiver and an associated transduce device, e.g., a pair of stereo headphones. The transmitter broadcasts an electrical signal which is representative of the electrical input signal provided to the main loudspeaker. The broadcast signal is received by the receiver and is demodulated and amplified to drive the transducer so that it produces augmented sound substantially in synchronism with the sound arriving from the main loudspeaker.

Abstract: An intelligent speaker unit is controlled by control data transmitted with the digital audio data. The intelligent speaker has a Digital Signal Processor (DSP) for processing the audio data in accordance with the control data. The control data contains an address to select the speaker unit. The DSP for the speaker unit processes audio data digitally based on parameters in the control data. The processed digital audio data is then converted to an analog signal which is amplified and applied to the speaker. The digital audio data is time division multiplexed on a TDM bus. Each time slot on the TDM bus contains audio data for one digital audio channel. The control data is placed on the TDM bus as one channel (time slot) or is distributed as control bits through all the other channels. The control data also contains channel select data. Accordingly the DSP in a selected speaker unit may in turn select its audio data from a plurality of audio channels based on the control data the DSP receives.

Abstract: A portable multimedia marketing system is useful for playing back prerecorded audiovisual presentations. A portable carrying case holds the various components which include an audio and video playback device for playing the presentations. A presenter's monitor is used by the presenter to monitor the video portion of the presentation and a hand-held customer monitor is used by the person to whom the presentation is directed for viewing the video portion of the presentation. A pair of loudspeakers removably mounted within the carrying case provide the audio portion of the presentation. While the loudspeakers may be removed, from the carrying case, they are designed to remain in the case during use. Various umbilicals provide power, audio and video signals to or from the individual components.

Abstract: A portable recording and reproducing apparatus is adapted to reproduce a melody recorded on a recording medium such as a magnetic tape and to amplify the melody and voice through a speaker as the voice is inputted from a voice input unit in tune with the melody. The apparatus is formed integrally by incorporating a sound recording medium accommodating portion, the voice input unit, and the speaker via a grip portion, and excels in portability.

Abstract: A portable audio apparatus allows a user to sing along with the recorded song, the user's voice and recorded song being outputted through a speaker. The apparatus permits the recorded lyrics or recorded tune of the song to be substantially eliminated prior to being reproduced by the speaker. The apparatus can operate in a fast forward or reverse mode and will stop between adjacent songs. A power savings circuit interrupts the supply of power to a motor to stop the latter from continuing to operate on a fast forward or reverse mode.

Abstract: A system for monitoring the integrity of speakers and their associated wires using the pair of audio wires without disconnecting the speaker from the audio source. A direct current is injected onto the audio signal path and directed via a high impedance path through the speaker coil while any audio signals present drive the speaker through a low impedance path. The magnitude of the direct current is then evaluated at a central switching location and based on the value of the current, the status of the signal path is known to be either a good path, an open path, a shorted path or a grounded path. Alarm initiating devices may be connected to the wire pair and can be connected in such a way that the current on the wire pair indicates the status of the alarm indicating devices distinct from the currents corresponding to signal path integrity.

Abstract: A portable recording and reproducing apparatus is adapted to reproduce a melody recorded on a recording medium such as a magnetic tape and to amplify the melody and voice through a speaker as the voice is inputted from a voice input unit in tune with the melody. The apparatus is formed integrally by incorporating a sound recording medium accommodating portion, the voice input unit, and the speaker via a grip portion, and excels in portability.

Abstract: A simultaneous interpretation system includes a plurality of simultaneous interpretation stations interconnected with a multi-conductor bus which carries up to thirteen audio lines. One audio line designated FLOOR connects to a microphone into which a source language is spoken. An interpreter located in a booth operates station controls which interact with the system. The interpreter may input select FLOOR or any one of twelve LANGUAGE lines for input to a headset and may output-select any one of the twelve LANGUAGE lines for output via a microphone. A three position microphone switch provides selective routing of the interpreter's voice from the microphone to an output-selected LANGUAGE line during "active" simultaneous interpretation, or back to the headset of the interpreter when not "active." Each booth houses two interpreters working as a team, with parallel interconnected controls, and each interpreter hears the other interpreter when their microphones are both not in the "active" mode.

Abstract: A portable music information reproducing and voice amplifying apparatus for reproducing music recorded on a recording medium and voice sound inputted through a voice input unit in unison through a speaker. The apparatus is integrally formed by incorporating a sound recording medium storage portion with the voice input unit and the speaker spaced apart, by a grip portion, to avoid feedback from the speaker to the microphone.

Abstract: A system for controlling the second field in auditorium having the feature that stage and audience seating areas are different acoustically, which includes a first assisted acoustics system whereby acoustical energy from the stage area is input, and then controlled acoustic energy is supplied to the audience seating area, and a second assisted acoustics which is provided independently of the first electronic acoustical augmentation system, whereby acoustical energy from the audience seating area is input, and then controlled acoustic energy is supplied to the stage area. Each assisted acoustics system includes acoustic energy input devices and acoustic energy output devices whereby a uniform rate of power decay coefficient can be effected throughout the hall, including spaces under balconies and the like. Significantly improved the degree of acoustic similarity between the stage area and audience seating area is achieved by controlling reverberation characteristics.

Abstract: This invention relates to a device for generating sound in a hall comprising a first space for dancers and/or listeners and an adjacent second space, for instance a catering space. According to the invention a sound-ceiling (4) is arranged in the first space (2) in a distance from the floor, and is a large number of loudspeakers (5) arranged in the sound-ceiling.

Abstract: A foreground music sound system includes at least one complementary array of speakers (12) comprising a bass frequency speaker (20) and a plurality of microspeackers (14-18). The complementary speaker array may be designed to provide full frequency response with substantially uniform sound coverage for a wide variety of acoustic environments. A current amplifier (25) is responsive to a music signal input and a microphone signal input to directly drive the speakers. The amplifier (25) is a high current, low impedance amplifier so that it is capable of driving a large number of speakers, without the need for matching transformers at each speaker.

Abstract: A public address system which consists of a longitudinal tubular member extending through an area serviced by the system, with a longitudinal opening and having a plurality of speakers spaced at regular intervals. The audio signals generated from the speakers are emitted through the opening in any direction desired. The speakers are hidden from view within the tubular member and by a cover on the opening which further protects the speakers from ambient contamination. Preferably, the tubular member consists of modular sections, each section including at least one speaker. The speakers may be controlled through a speaker control circuit.

Abstract: A device for providing limited-access volume control for at least one remote speaker in an audio system, the device comprising a lockable, key-actuable attenuator that attenuates an input audio signal to provide an attenuated output audio signal. The attenuator is adjustable upon the insertion of a key to selectively adjust the degree of attenuation, and is lockable upon the removal of the key to prevent unauthorized adjustment of the degree of attenuation. The attenuator preferably comprises a transformer having primary and secondary windings. A plurality of tap means is connected to the secondary winding. A lockable, key-actuable, multiple position switch, having a contact corresponding to each switch position, is connected to the tap means with each contact being connected to one of the tap means. The switch can be operated upon insertion of a key to move from position to position and can be locked upon removal of the key.

Abstract: A foreground music sound system includes at least one complementary array of speakers (12) comprising a bass frequency speaker (20) and a plurality of microspeakers (14-18). The complementary speaker array may be designed to provide full frequency response with substantially uniform sound coverage for a wide variety of acoustic environments. A current amplifier (25) is responsive to a music signal input and a microphone signal input to directly drive the speakers. The amplifier (25) is a high current, low impedance amplifier so that it is capable of driving a large number of speakers, without the need for matching transformers at each speaker.

Abstract: A public address amplifier comprises a housing which contains an output amplifier connected to loudspeakers. A microphone containing a microphone transducer and an input amplifier is connected to the input of the output amplifier and to connectors on the housing by a cable. A second such public address amplifier can be connected to the first by connecting its cable to one of the connectors so as to provide a public address system of increased power.

Abstract: An audio system having a voice override and voice amplification control circuitry is provided. The system provides high quality music to a listener through a set of headphones and includes a microphone and a foot operated switch to allow a user to override the music signal to communicate with the listener. The foot switch initiates a ramp voltage signal generator which gradually attenuates the normal music signal to a predetermined level and gradually increases the level of the voice signal and mixes it with the music signal. When the voice signal terminates, the music gradually returns to its normal level when the foot switch is deactivated resetting the ramp voltage signal generator.

Abstract: A device having two sets of oppositely facing corresponding resonance cavities; i.e., an upper and a lower resonance cavity. Each of the resonance cavities include a piezo-electric type diaphragm consisting of a vibration diaphragm and a start-up plate. Electric signals cause the piezo-electric type diaphragm to vibrate back and forth and produce sound waves from the upper and lower resonance cavity.

Abstract: A voice evacuation system using pulse width modulation of square waves at a frequency substantially higher than the voice signals. A number of amplifiers are connected in parallel to the distribution circuit. The signal from each amplifier is examined for the presence of the square waves. If no square waves are present, the amplifier is automatically disconnected from the distribution circuit. The remaining amplifiers are of sufficient capacity to carry the required load. The high frequency components are flitered from the signal before it is applied to the distribution circuit, leaving only the audio signals.Because of the nature of the coupling to the distribution circuit, a monitoring voltage and signals to operate auxiliary devices may be applied to the distribution circuit for supervision and operation of the auxiliary devices during actual operating conditions.

Abstract: The invention relates to acoustically radiating randomly large rooms and surfaces according to propagation time principles, whereby action or representation and reception or listening areas border directly on one another or are identical. Its object is to avoid error locations and skipping effects caused by movements, which are especially interfering for important solo sound sources. The resulting object of realizing a propagation time staggering without limiting source areas, and responding to the acoustic capacity of the sources, is solved by means of a control device connected to the delay or amplification devices, and which differentiatedly controls them analogous to the sound paths between the source and the acoustic radiator locations.