[Secondary auditory risks from listening to portable digital compact disc players]

The recent availability of portable high-performance digital disc-players in addition to cassette players, and with an increased dynamical range, has enhanced the risk to hearing for their users. The present study aimed at attempting to evaluate this hazard. After selection of a digital player, 12 normally-hearing voluntary subjects were exposed to listening to two records (classical music and hard-rock) at an acoustic level complying with safety regulations. Their temporary threshold shifts (TTS) were determined at 4 and 6 kHz just after exposure. The 0.5 kHz auditory thresholds were also measured as a control. At 4 and 6 kHz, the average value of TTS was 5 dB (standard deviation 3.1 to 5.9 dB). There was no statistically significant difference neither between the TTS at 4 and 6 kHz (p > > 0.05), not between TTS for the two types of music. A voluntary subject, suffering from a mild high-frequency hearing loss, was also tested. His TTSs were higher than average and may have corresponded to slower recovery (may be non monotonous). Therefore special caution should be recommended in such cases. The measurements have pointed out that very high acoustic levels could be reached (125 to 127 dBA) with a Leq (1 hour) od 110 dBAi.e. much higher than tolerable levels. Thus there is a serious risk to hearing, possibly increased by high level transients. Moreover, better headphones are likely to provoke TTS also above 8 kHz, which might be evaluated by high-frequency audiometry.(ABSTRACT TRUNCATED AT 250 WORDS)