Active hearing protectors

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. This causes the inputs to the power amplifiers to fall when the input to the preamplifiers increases beyond a certain level. A balanced attenuation circuit arrangement is employed which reduces the size of too-large sound waves without altering their shape, whereby the volumes of the two stereo channels are maintained in the proper relation to each other to preserve binaural hearing.