A holder is provided for securing a microphone or earpiece in position inside a helmet. The holder comprises a plurality of tubular rings of soft flexible material. One ring is adapted to be connected to a shell of the helmet, and the other rings are serially connected by resilient, short, thin, soft segments. The rings are dimensioned and arranged so that they can be nested within each other or pulled out to form an extending holder. A microphone or earpiece may be connected to one of the said rings.

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.

A baffle, which supports a driver for converting an input electrical signal into an acoustical output signal, is mounted to a headphone cup via a first cushion which sufficiently spaces the baffle from an outer ear to avoid contact. The baffle defines a front cavity and a rear cavity. A second cushion which forms an oval opening large enough to encompass the outer ear is mounted on the headphone cup for establishing an air seal between the front cavity and a region outside the headphone cup.

A sound actuated detector comprising a microphone, an elastic cylinder having a flexible bottom adapted to fit tightly around the microphone with the sensing surface of the microphone fitting tightly against the flexible bottom, a mounting base connected to the surface of the cylinder having the flexible bottom, an elastic isolating medium arranged between the base and the surrounding surface to which the detector is attached, and a weight connected to the microphone having a mass such as to eliminate movement of the microphone in response to frequencies above a selected frequency.

An inertial transducer is provided comprising a housing containing therein a magnetic circuit including components thereof separated by a spring diaphragm wherein the flexing of the diaphragm causes the components to move toward and away from each other to induce a current in a coil. The spring diaphragm served to separate the housing into two tuned cavities, the frequencies of which differ from each other and from that of the spring diaphragm. The transducer has frequency response peaks at the resonant frequencies of the cavities and spring diaphragm.