There is disclosed apparatus for providing improved hearing acuity in the presence of high intensity background noise, such as that which exists at an industrial site. The apparatus employs an input microphone which is adapted to receive audio information including noise from the environment. The output of the microphone is applied to an expander circuit, which functions to expand the high pass audio frequency band according to the nature and intensity of the noise. In a first mode expansion is provided at a variable ratio and threshold which are selected according to environmental noise. The expanded audio signal is applied to a compressor limiter module to reduce the level and limit the amplitude of the signal within predetermined and safe limits. The compressor limiter output signal is applied to an adjustable low pass filter, which serves further to accommodate the processed signal to a particular user and to limit the frequency range of the output signals. This low pass filter has an output applied to a linear attenuator which serves to reduce the amplitude of the processed signal depending upon the particular noise levels at the site. This output signal is applied to a speaker which is located in proximity with the ear of a user to allow him to communicate relatively normally in high noise environments. Additional modes are described which employ both expansion and compression prior to limiting.

An active in the ear hearing protector having an ear piece (13) and a casing (12) attachable to the ear piece, the ear piece being positionable in the ear canal of a user so as to peripherally acoustically seal the ear canal and such that the attached casing (12) is positioned externally of the ear canal. The casing (12) incorporates a microphone (14) for receiving external acoustic sound signal and a signal processing circuit (15) for receiving electrical signal from the microphone and correspondingly causing a loudspeaker (16) in the casing to generate sound signal for direction down a tube (34) extending through the ear piece to be transmitted to the ear canal. The electrical circuit (15) is arranged to limit the electrical signal delivered to drive the loudspeaker whereby to limit the sound pressure of sound signal delivered from the loudspeaker to the ear canal via the tube (34).

A hearing protector for providing protection from high volume sound waves. The protector is a headset including earmuffs, at least one of which contains a microphone for receiving sound waves and a speaker for transmitting sound waves to the ear of a person wearing the headset. The signal to the speaker is filtered to reduce the amplitude of any frequency components outside of a predetermined audio frequency range. A CMOS integrated circuit is connected as an active voltage sensitive variable resistance element of a control circuit for automatically limiting the volume of the sound waves provided by the speaker, in response to variations in the level of the sound received within the predetermined audio frequency range.

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. Connectors for connecting recorders and a boom microphone, and function selection switches are provided by the control means for connecting circuit components of the control unit selectively for performing the above functions. The input and output transducers have oppositely oriented diaphragms mounted in a common plane to provide an inverted acoustic wave in real time for combining with and substantially cancelling an incoming acoustic wave. In this embodiment, an isolation wall means may also be incorporated to prevent sound from the output transducer from propagating back into the input transducer. In a second embodiment, the input and output transducer are both oriented in the same direction toward the user's ear canal.

A sound attenuating earcup assembly having ambient communication capability without the necessity of removing the assembly in which a cup or shell adapted to fit over the wearer's ear is made of a relatively hard sound attenuating material and is formed with three wall openings each extending from the outer surface of the shell to the interior and each of which is provided with an external countersink. The first opening receives the battery casing having an externally removable cover which holds the casing onto the shell with its terminals located within the shell. The second opening receives the outside communication unit with the microphone facing outwardly and the major portion of the unit and its terminals retained inside the shell by a detachable fastener. The switch actuating element extends outwardly through the third opening from the body of the switch carrying the switch terminals. A protective sleeve screwed onto a portion of the switch post to hold the switch in position surrounds the actuator to reduce the possibility of accidental actuation. The earphone is disposed in a recess in a pad of sound absorbing material in the shell. Where the assemblies are used in pairs for a binaural effect only one assembly is provided with a switch. Means is provided for connecting the earcup carried elements to external electronics so as to charge said battery from a power source in said external electronics.