headset 12 includes a voice microphone 64 which is supported in front of the wearer 39 s face by means of a boom 66 adjustably secured to left earcup assembly 28 by a clamp 70 the microphone 64 is electrically connected to the headset through a cable 68 microphone 64 is coupled to the microphone signal line 22 through a normally open 34 push to talk 34 switch 72 located in the right earcup 30 actuation of a lever 74 mounted outside the earcup 30 momentarily closes switch 72 to couple the microphone 64 through mixer 18 to the amplifier 20 which provides an amplified signal on the common audio signal line 26 suitable matching of the signal levels of the radio receiver 16 and the voice microphone 64 may be accomplished by adjusting the amplification of the respective inputs to mixer 18 while a boom mounted voice microphone is used in the embodiment shown it may be preferable in certain situations to use a contact microphone urged against a suitable portion of the wearer 39 s head such as the temple area such a microphone is described in detail in the copending application of applicant leonard p frieder jr and jackson a aileo ser no 641 450 filed dec 17 1975 which application is incorporated by reference it will be seen that we have accomplished the objects of our invention each earphone is responsive to a composite signal comprising a common audio signal and a second signal derived only from a local ambient sound microphone our system is electrically efficient since each voice coil is coupled directly to an approriate amplifier output without any isolating resistors the cost and bulkiness of our system is comparable to those using.