In-situ Audiometry Compared to Conventional Audiometry for Hearing Aid Fitting

Abstract

The use of in-situ audiometry for hearing aid fitting is appealing due to its reduced resource and equipment requirements compared to standard approaches employing conventional audiometry alongside real-ear measures. However, its validity has been a subject of debate, as previous studies noted differences between hearing thresholds measured using conventional and in-situ audiometry. The differences were particularly notable for open-fit hearing aids, attributed to low-frequency leakage caused by the vent. Here, in-situ audiometry was investigated for six receiver-in-canal hearing aids from different manufacturers through three experiments. In Experiment I, the hearing aid gain was measured to investigate whether corrections were implemented to the prescribed target gain. In Experiment II, the in-situ stimuli were recorded to investigate if corrections were directly incorporated to the delivered in-situ stimulus. Finally, in Experiment III, hearing thresholds using in-situ and conventional audiometry were measured with real patients wearing open-fit hearing aids. Results indicated that (1) the hearing aid gain remained unaffected when measured with in-situ or conventional audiometry for all open-fit measurements, (2) the in-situ stimuli were adjusted for up to 30 dB at frequencies below 1000 Hz for all open-fit hearing aids except one, which also recommends the use of closed domes for all in-situ measurements, and (3) the mean interparticipant threshold difference fell within 5 dB for frequencies between 250 and 6000 Hz. The results clearly indicated that modern measured in-situ thresholds align (within 5 dB) with conventional thresholds measured, indicating the potential of in-situ audiometry for remote hearing care.

Keywords: auditory rehabilitation; connected hearing care; in-situ audiometry‌; remote hearing aid fitting; tele audiology.

Figure 1.

Example of an open-fit hearing aid (Oticon) programmed for two standard audiograms (N2 and N3). For each standard audiogram, the hearing aid is configured either using in-situ or using the conventional audiogram. The left panel shows the measured real ear aided response (REAR), while the right panel shows the differences between these REAR curves for each degree of hearing loss (i.e., for each standard audiogram). Each curve represents the mean of ten measurements. Shaded areas, omitted for clarity in the left panel, indicate  ± one standard deviation.

Figure 2.

The difference in SPL between open/closed and open conditions for each hearing aid model. Error bars represent  ± one standard deviation.

Figure 3.

The difference in SPL between open/closed and closed conditions for each hearing aid model. Error bars indicate  ± one standard deviation.

Figure 4.

Participants’ in-situ audiometry thresholds measured with four different hearing aid models relative to the participants’ thresholds measured with conventional audiometry. Note that only two data points were collected at 125 Hz. Error bars are shifted for better visibility.