Abstract: A device for performing electroacoustic functions including noise cancellation, hearing aid, communication interface, headset, feed for recording device, and headphone functions. The device includes composite transducers connected to a control unit. The composite transducers can be mounted on a headband and are configured to include input transducers for converting acoustic waves into electrical signals for processing by a control unit, and output transducers for converting the processed electrical signals to processed sound waves. The control unit includes an inverter/amplifier and a mixer/output amplifier for inverting the electrical input and controlling the gain for either adjusting the gain to maximize a noise cancellation function or increasing the gain beyond the minimum level heard by the ear to a desired level for a hearing aid function.

Abstract: The present invention is concerned with a receiver device for converting electrical signal from a headphone, a telephone receiver or the like into acoustic signals. More particularly, it relates to a noise reducing receiver device in which acoustic signals in the vicinity of an electro-acoustic transducer element are converted by a microphone into electrical signals and negatively fed back to an amplifier circuit which is adapted for amplifying input electrical signals and supplying the amplified signals to the electro-acoustic transducer element. In the noise reducing receiver device, the input electrical signals are amplified by the amplifier circuit and converted by the electro-acoustic transducer element into output acoustic signals. A microphone is arranged in the vicinity of the electro-acoustic transducer element and adapted for converting the output acoustic signals and external noise into electrical signals, which are negatively fed back to the amplifier circuit via a feedback circuit.

Abstract: An audio compression system wherein the compression theshold may be adjusted to a calibrated level. The audio compression system is utilizable in a receiver system whereinan audio input signal received by the receiver system via a communications channel is applied to conditioning circuitry. The conditioning circuitry, in turn, provides a conditioned input signal to an acoustic transducer element for generating a corresponding audio output signal. The audio compression system compares the conditioned input signal and an initial threshold signal to provide a comparator output signal corresponding to the difference between the conditoned input signal and the initial threshold signal. The comparator output signal is provided as a control input to the conditioning circuitry. If the conditioned input signal exceeds the initial threshold signal for a preselected period of time, then the initial threshold signal is switched to a second threshold signal.

Abstract: Microphones sample the sound output from the speakers of a sound amplification system. The resulting time domain analog signals undergo a Fast Fourier Transform which yields frequency domain signals representative of the intensities of the frequency bands which compose the sound. The intensities or levels of each band are compared to stored permissible level limits for each frequency band. Attenuators respond to signals indicative of band levels being exceeded by respectively attenuating the frequency bands to which they are tuned so the speaker output does not contain frequencies which exceed permissible limits. The time weighted permissible averages for each frequency are also integrated to provide for production of signals representative of the cumulative sound dosage.

Abstract: A device for performing electroacoustic functions including noise cancellation, hearing aid, communication interface, headset, feed for recording device, and headphone functions. The device includes composite transducers connected to a control unit. The composite transducers can be mounted on a headband and are configured to include input transducers for converting acoustic waves into electrical signals for processing by a control unit, and output transducers for converting the processed electrical signals to processed sound waves. The control unit includes an inverter/amplifier and a mixer/output amplifier for inverting the electrical input and controlling the gain for either adjusting the gain to maximize a noise cancellation function or increasing the gain beyond the minimum level heard by the ear to a desired level for a hearing aid function.

Abstract: Improvement in active noise reduction based on a negative feedback electro-acoustical system which consists of an Electronic Earplug seated in the concha fossa combining active and passive noise reduction in the quiet zone at the ear, a bilateral transducer circuit which drives a speaker as an acoustical velocity source, a shunt feedback control filter network which improves stability and increases noise reduction, and a combined input noise-filter/feedback system. A typical application is in a noisy environment for hearing protection and for improved communication capability, e.g., in vehicular communication, telephone, intercom, hearing aids, and stethoscopes.

Abstract: A sound cancellation system wherein a pair of sensors and actuators are positioned immediately adjacent an associated ear of an inhabitant of an enclosure so as to provide a cancellation zone immediately adjacent an associated ear without interfering with adjacent zones. A controller receives a synchronization signal so as to cancel a selected noise associated with a synchronization signal. The sensors and actuators are mounted to a seat which is to be occupied by an inhabitant of the enclosure.

Abstract: A combination ear protector and communications headset particularly adapted to the rugged, lightweight, convenience needs of aircraft ground crew members that are required to work in a hazardous noise environment. The headset includes two earplug-type transducers that function as a combination ultrasensitive microphone and speaker which are automatically inserted into the user's ears when the invention is disposed for use, thereby sealing the interior of the ear from ambient noise. In the ear protection mode of use, the headset is quickly and easily convertible to communications usage.

Abstract: The effectiveness of electronic earmuffs is improved by incorporating a mechanism which causes the middle ear muscles to contract before an intense sound is generated. This contraction is achieved by incorporating a wireless receiver into the earmuff. Immediately prior to the generation of the intense sound, the wireless receiver receives a signal which causes it to generate a loud, non-damaging sound in a loudspeaker in the earmuff. The received signal is generated by a radio frequency transmitter that is activated immediately prior to the activation of the mechanism producing the intense sound. The non-damaging loud sound from the loudspeaker causes the middle ear muscles to contract (this is a natural reflex of the ear). The intense sound is received outside the earmuff before the reflex contraction of the middle ear muscles has been relaxed.

Abstract: In order to overcome problems in an active noise reduction system of sound buffets at low frequency and signal enhancement caused by imperfect transfer functions of a noise cancelling sound generator and a microphone, one or more high pass filters for reducing low frequency signals are provided in a feedback loop between the sound generator and microphone. A low pass filter is provided for extending the bandwidth of the system but which does not introduce unduly large phase shifts.

Abstract: A protective earmuff which transmits normal sound levels and clips higher amplitude sound levels by causing an amplifier to go into saturation when the input signal is greater than a preset amount. The sound is received by a microphone, amplified and transmitted to the ear of the user by a speaker. The output of volume level is controllable independently of the clipping level. Also disclosed is a circuit allowing user control of both the clipping level and the volume level independently.

Abstract: A voice signal compression system wherein the compression threshold may be adjusted to a calibrated level. The system includes a variable gain amplifier for amplifying a voice input signal based on the application of a variable control voltage. A driver increases the power gain of the amplified input signal to provide a power-boosted output signal. In addition to applying the power-boosted output signal to an acoustic output transducer, the power-boosted output is also applied both to a peak detecting comparator and to a threshold reset timer. The comparator produces a digital output that triggers an attack/decay timing generator which produces the control voltage for the variable gain amplifier. The comparator initially is set to a high threshold state by the threshold reset timer. As the levels and peaks of the input signal increase, the comparator begins to trigger digital pulses to the attack/decay timer.

Abstract: In a hearing device, such as a circumaural earmuff cup or a circumaural earphone cup, either of which comprises an earpad assembly in contact with the external ear, through which sound is conducted to the external ear for the purpose of providing at the eardrum a sound pressure having a prescribed ratio with respect to the sound pressure at a source, the invention comprising a predetermined sound leakage path through said earpad assembly, to reduce the variable in said ratio, that is customarily encountered caused by the variations in the shape of the external ear from one user to another and by variations in position and force of contact of the earpad resting against the pinna.

Abstract: The invention relates to a method and to apparatus for attenuating externally originating noise reaching the eardrum while still enabling communication via an electro-acoustic path. Apparatus according to the invention comprises passive attenuation means disposed about each ear and delimiting a cavity (10). In addition it includes active attenuation means comprising a loudspeaker (6) placed inside the cavity (10) and a microphone (8) placed in the external ear duct or at the inlet thereto, said loudspeaker and microphone being interconnected by a constant gain amplifier (11) and an active analog filter (12) of the polynomial type, with the passive components thereof being designed to provide a given transfer function. One application lies in the construction of protective headsets fitted with incorporated loudspeakers enabling electro-acoustic communication.

Abstract: A combination ear protector and communications headset particularly adapted to the rugged, lightweight, convenience needs of aircraft ground crew members. The headset includes a noise cancelling microphone mounted directly on the headband where disposition either before the user's mouth or in an out-of-the-way on-top-of-the-head position is possible. In the ear protection only mode of use, the headset is disclosed to be optimally clean and unencumbered, but is quickly and easily convertable to communications usage.

Abstract: A signal compression system includes a plurality of channels. A plurality of these channels include a bandpass filter (for filtering out all but a portion of an input signal), an intensity detector (for deriving a spectrally weighted estimate of the intensity of a broader spectral portion of the input signal than the bandpass filtered spectral portion), and a divider (for compressing the bandpass filtered spectral portion using a variable gain having a preselected functional relationship to the spectrally weighted intensity estimate). The signal compression system preserves cross-channel information.

Abstract: A hearing protective device consisting of a headset having opposite earmuff and/or earplug assemblies resiliently connected by a headband assembly including a normally open power switch closed when the headband assembly is put on the user's head. The switch controls the energizing of the electrical circuitry of the device. Each earmuff and/or earplug assembly has an outwardly-facing microphone and an inwardly-facing sound reproducer, connected to circuitry defining respective stereo channels, each channel including preamplifier circuitry and a respective power amplifier drivingly connected to one of the sound reproducers. The circuitry also includes a hyper AGC circuit which receives and sums signals from the amplifier chain and derives attenuation signals therefrom which are fed back to the amplifier circuitry and which reduces the gain of this circuitry when the input sound exceeds a certain level.

Abstract: Apparatus for improving the audibility of incident sound (4) to a person (3) operating in an environment where there is a substantial background noise field (2) coming from a source (1) of repetitive noise, comprises an adaptable waveform generator (7), a first electro-acoustic transducer (10) receiving a synthesized cancelling waveform from the generator (7) and generating a cancelling noise to at least partly null the background noise, a second electro-acoustic transducer (11) to sense the partially nulled background noise, and adaptor (13) to modify the output of the generator (7) on the basis of the electrical output signal from the second transducer to minimize the nulled background noise, and sensor (5) to feed a triggering signal (6) derived from the source to the waveform generator. The electro-acoustic transducers (10, 11) can be mounted in headset (8) holding the transducers adjacent to an ear of said person without substantially impeding the arrival of said incident sound (4) to said ear.

Abstract: A protection circuit for limiting the sound pressure level provided by transducer loads, such as headphones, in which there is provided interconnections between the input to the transducer load and the transducer load such that when loudness exceeds a predetermined limit, the connection to the transducer load is opened and the circuit turns off the audio signal to the transducer load and optionally illuminates an LED. After a predetermined time interval, the circuit automatically resets; however, if the sound pressure level has not been reduced below the predetermined limit, the circuit again immediately turns off the audio signal to the transducer load and this is continued until such time as the sound pressure level is reduced below the predetermined limit.

Abstract: A sound detecting device for amplifying distant or weak sounds, including a novel loud sound suppressing circuit for temporarily shunting the amplifier input signal to ground whenever the amplifier output signal exceeds a predetermined amplitude. The microphone, amplifier, and sound suppressing circuit are mounted in a wand shaped much like a flashlight. The wand can be attached to headphones.