Music and hearing aids

Hard-of-hearing musicians have long complained about the poor sound quality they experience while playing their instruments or when listening to music through hearing aids. Indeed, many non-musicians also complain of the reduced sound quality of music heard through their personal amplification. This article is a study of one electroacoustic parameter that, together with three other less important parameters, delineates the optimal amplification scheme for hard-ofhearing musicians and for others who simply like to listen to music. In addition to the experiment reported here, this study is based on clinical experience with more than 350 hard-of-hearing musicians who have been successfully fitted with hearing aids over the last 15 years at the Musicians’ Clinics of Canada (www.musiciansclinics.com). Traditional approaches by the hearing aid industry to optimize a hearing aid or a program within a hearing aid for music are varied. Some manufacturers have sought to reduce the low-frequency amplification and output; others have tried to increase this gain and output. Still other manufacturers have used a strategy of increasing mid-frequency gain and output to optimize the “long-term” spectrum of music. These approaches have met with only limited clinical success. One reason is that music spectra, unlike those of speech, are quite variable. Another reason is that the input to the hearing aid of speech differs from that of music. HOW SPEECH AND MUSIC DIFFER The most intense components of speech are the “low back” vowels. e.g., [a] as in “father.” At the level of the listener’s ear, these sounds, even if shouted, rarely exceed 85 dB SPL and are more typically 75-82 dB SPL. In contrast, the more intense elements of music measured at the same ear level location are on the order of 100-110 dB SPL, with occasional peaks about 118 dB SPL. This is true not only of rock, but of classical music as well. Since most engineers have had speech input in mind when designing hearing aids, it is understandable that the “peak input limiting level” of hearing aids has been set to about 85 dB SPL. Peak clipping or limiting may occur at various points in a hearing aid, but if it occurs before the gain-controlling elements, or the A/D converter, adjusting hearing aid settings will not prevent it. Hearing aids are normally designed so that this does not happen for the peak levels encountered in speech, but the peak levels encountered in music may well cause clipping in the early stages of the hearing aid amplifier. This parameter is not found on hearing aid specification sheets. The usual peak input limiting levels are very reasonable for speech since the most intense components are less than 85 dB SPL. Anything of greater intensity is presumed not to be speech and is therefore limited. The peak input limiting level is not reported on ANSI hearing aid specification sheets, so one needs to speak with someone in the