Speech understanding in noise with earplugs and muffs in combination

An experiment was conducted to determine the effect on speech understanding of an earplug and muff, worn in combination. Two groups of 12 normal-heari ng subjects were tested individually in a semi-reverberant chamber. The mea surements included free-field assessment of hearing thresholds from 0.25 to g kHz and consonant discrimination, with the ears unoccluded or fitted wit h E-A-R foam plugs, the Peltor Aviation communication headset, or the two d evices in combination. The headset had active noise reduction (ANR) capabil ity, and was tested without and with ANR operational. The speech was presen ted at a level of 85 dB SPL either in speech spectrum noise (Group 1) or ca ble swager noise (Group 2), presented with speech-to-noise ratios ranging f rom +5 to -10 dB. The two noise backgrounds differed in terms of both energ y spectrum and temporal characteristics. The results showed that below 2 kH z, the devices worn in combination provided as much as 30 dB more sound att enuation than either device alone. The effect of the combination on consona nt discrimination was a decrease of only 4%. The type of noise background a nd speech-to-noise ratio proved to be more important determinants of outcom e. (C) 1998 Elsevier Science Ltd. All rights reserved.