New Headset-Microphone for Military Use
Martin L. Touger · The Journal of the Acoustical Society of America · 1958
The H-157(XA)/AIC is a new headset-microphone developed for the Air Force under contract AF 33(600)33172. In comparison with the II-78B/AIC now in general use, the H-157 has the following improvements: (1) weight is reduced 39%; (2) comfortable wearing time is in excess of 8 hr, an improvement of over 100%; (3) the noise attenuation is increased 10 to 15 db; and (4) the noise-to-noise PB word articulation score in 120 db jet noise is 71%, an increase of 20 points. In addition the headset has a substantially flat real-ear response, resulting in greatly improved speech quality. The H-157 employs a circumaural hard-shelled ear cushion with a foam- or liquid-filled sealing pad. The earphone used is the H-143/AIC, which weighs 35 g, has a 1000-cps sensitivity of 105 db/mw on a 6-cc coupler, and a substantially uniform coupler response to 5000 cps. With one watt power available and 10 db peak clipping, the headset will give an estimated 66% word articulation with the talker in quiet and the listener in 140 db of jet noise. The signal level at the ear is 115 db. The microphone, M-87(XA)/AIC, is much smaller and lighter than its predecessor, the M-33, and is lower in sensitivity. The sensitivity is adequate for use with the AN/AIC-10 and related systems.