It seems reasonable to postulate that if a patient has a hearing impairment at particular frequencies, selective amplification at those frequencies would be an advantage. Attempts have been made in the laboratory to show that when this is done scores on various audiometric tasks will improve. Whether such laboratory benefit will be preferred by patients in their daily life is another matter. Despite a lack of knowledge on this subject, modifications are frequently made to a hearing aid system in the expectation that this will improve auditory performance and hence be preferred by the patient. The most common modifications made to an ear level aid in the British National Health Service are adjusting the tone control and venting the ear mould with the aim of emphasizing the higher frequencies.
A randomized crossover study was carried out in 83 first time hearing aid users with a mild to moderate hearing impairment to assess whether a hearing aid at the ‘H’ tone setting and with a 2 mm vented mould would be preferred by those with a more marked high frequency impairment. BE series aids were used so that any findings could be directly translated to NHS practice.
No consistent preference for the modified system was identified when patients were subgrouped according to the overall slope (0.5 to 4 kHz) of their audiogram. However, when the slope between 0.25 and 1 kHz, which corresponds to the real ear effect of these modifications, was analyzed patients with a slope at these frequencies preferred the high-tone emphasis system (p<0.005). A second but lesser predictor of preference was age, those under 66 years preferring a modified and those over 69 years preferring an unmodified system (p<0.05).
These findings need to be confirmed using different methods of altering the frequency response. What acoustical effect these achieve in a specific patient need to be confirmed using ‘in the ear’ measures before any preference they might have can be related to the configuration of their audiogram.