The use of high stimulus rate auditory brainstem responses in the estimation of hearing threshold.

This normative study investigates the efficiency of using the maximum length sequence (MLS) technique applied to auditory brainstem evoked response (ABR) testing to estimate hearing thresholds. Using a commercially available system, ABRs were recorded in sixteen subjects at two conventional rates--9.1 and 33.3 clicks/s--and six MLS rates between 88.8 and 1000 clicks/s. Each subject was tested at five stimulus levels from 60 down to 10 dBnHL. The wave JV amplitude input-output (I/O) functions, relative signal to noise ratio (SNR) and speed of test were calculated for all conditions. The JV amplitude and detectability decrease as the stimulus rate increases and level decreases. The latency of JV increases as the stimulus rate increases and the intensity decreases. While the slope of the amplitude I/O function was maximal at 200 clicks/s, at 300 clicks/s it was comparable with that obtained at conventional rates. At higher rates, the slope of the I/O function decreases. When compared with the conventional recording rate of 33.3 clicks/s there is a small improvement in SNR for MLS rates between 200 and 600 clicks/s at levels above 30 dBnHL. The calculated speed improvement at 300 clicks/s is a factor between 1.4 to 1.6 at a screening level of 30-40 dBnHL. It is felt therefore that there may be a small advantage to using MLS in screening and that the optimal rate for this lies at around 200 to 300 clicks/s. However even at these rates, as a consequence of the adaptation of the response with both rate and level, the improvement in SNR or speed of test would be modest when estimating threshold.

An evaluation of a group follow-up scheme for new NHS hearing aid users.

Group follow-up of hearing aid patients has been implemented in a number of Audiology departments in the UK. This paper describes a retrospective analysis to investigate the efficiency and effectiveness of group follow-up sessions compared with individual follow-up sessions for new NHS hearing aid users in one such department. Questionnaires were sent to 98 patients; half had attended group follow-up (GF) and half had attended individual follow-up (IF) sessions. The questionnaire assessed their use of, self-rated performance and satisfaction with the hearing aid. The two follow-up systems were also analysed with respect to staff time, costs and attendance rates. Results showed a significant difference between groups for self-rated performance (GF better than IF) but none for hours of use or satisfaction. GF attendees were generally more positive about their hearing aid, required fewer additional follow-up appointments and reported more benefit in various listening situations. Although GF sessions cost less to run, there is a minor capital cost in setting them up. Attendance rates were significantly poorer for GF sessions but this study did not address the reasons for this finding. Overall, results suggest that GF is a cost effective method of following up typical new hearing aid users and may convey distinct advantages to patients that attend. However, a group follow-up session may be a less attractive option than individual follow-up for some new hearing aid users.