Acoustical performance of the Communications Ear Plug (CEP) in combination with the Gentex SPH-5 flight helmet


  1. Abel, S.M.
  2. Crabtree, R.B.
  3. Odell, P.
  4. Dunn, G.
Corporate Authors
Defence R&D Canada - Toronto, Toronto ONT (CAN)
An experiment was carried out to measure the real-ear attenuation at threshold provided by the Communications Ear Plugs (the CEP) and Gentex SPH-5 flight helmet with communications capability, worn alone or in combination. Word recognition in quiet and in Helicopter and Sea King noise was also assessed under the three ear conditions. Like the standard issue Aearo E-A-R® foam ear plugs, the CEP worn in combination with the helmet has the capability of increasing the sound attenuation achieved at low frequencies. The CEP has the added advantage of improving the speech-to-noise ratio of the communications channel. Ten subjects with normal hearing were tested. The results showed that the two devices worn in combination provided significantly greater attenuation than the helmet worn alone, by 6-16 dB over the frequency range tested. The best predictor of outcome at each frequency (0.25-8 kHz) was the addition of 5 dB to the higher of the attenuations realized for the devices worn alone. When the devices were worn in combination the level of speech required to achieve a 60% correct word recognition score decreased by about 18 dB due to a 13-dB increase in the absolute level of the speech reaching the ear in combination with a 5-dB increase in the attenuation of the external noise.

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Report Number
DRDC-TORONTO-TR-2003-077 — Technical Report
Date of publication
01 Jun 2003
Number of Pages
Electronic Document(PDF)

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