Abstract: A microphone assembly suitable for use with a face mask has a cylindrical housing with an inwardly extending recess at its front end covered by a first diaphragm. A microphone unit carried by the housing has a diaphragm communicating with the recess, and the recess and the two diaphragms define an airtight chamber containing a trapped quantity of air transmitting vibrations of the first diaphragm to the microphone diaphragm. A doubly adhesively sided pad comprising a layer of plastic closed cell foam material and two adhesive films provides an intimate vibration transmitting interface, free of air flow passages or pockets, between the diaphragm and a supporting surface.

Abstract: The presence of human voice signals in audio signals is detected by a method and apparatus based on the recognition that fundamental frequency components of human voice signals are separated from one another by a characteristic frequency difference ranging from about 120 hertz to about 180 hertz. A limited frequency band portion of the audio signals is mixed and filtered to produce a signal containing the difference frequencies of the frequency components included in the limited frequency band portion of the audio signals, and the latter signal is processed to determine whether it contains a component of significant magnitude representing the human voice characteristic difference frequency.

Abstract: A conventional hearing aid for a hard-of-hearing person has a microphone input for sensing sounds or voice communication. In a high noise environment, a somewhat remotely located speaker wishing to communicate with the person talks into a microphone input to a transmitter so that his spoken word is transmitted as a modulated carrier wave. The hard-of-hearing person is provided with a receiver which receives and detects the modulated carrier wave. The detected signal is applied to a transducer to reproduce the spoken word. A hollow elongated conduit comprising a flexible tube having a small bore extending therethrough, conducts the audible sound representing the spoken word from the transducer to the microphone input of the hearing aid, thus enabling the wearer of the hearing aid to hear the remotely spoken sounds of a lower level than the ambient noise while at the same time hearing the ambient noise. The conduit may contain a wire for acoustic loading and/or structural strength.