In-situ audiometry: How close is it to conventional audiometry?

Technology in the hearing aid industry is ever changing. One of the many features that may improve accuracy of hearing aid fi ttings and patients ’ satisfaction is the inception of in-situ audiometry, which allows the clinician to measure hearing thresholds with a hearing aid in the patient ’ s ear. Objective : The present study aimed to investigate the validity of in-situ audiometry measured with a behind-the-ear hearing aid coupled to a customized earmould relative to conventional thresholds measured using supra-aural head phones . Study design : A total of 24 ears from 15 participants with varying degrees of sensorineural hearing loss ranging from moderate to severe, were selected for the study. Pure tone hearing thresholds and real-ear-to-dial-differences were measured for both conventional and in-situ thresholds across 250 Hz to 6 kHz. Results : Slight but signifi cant mean differences ( p 0.05, paired t -test) of 3.2 and 3.4dB between conventional and in-situ thresholds at 2000 and 6000 Hz were found before adding REDD corrections with in-situ thresholds yielding better (lower) thresholds. Except at 250 Hz in dB HL, individual threshold variability between conventional and in-situ threshold measurements was within or equal to 10dB for  95% of ears before and after adding REDD corrections. Large interparticipant variation in measured ear canal SPL was noticed at 250, 500, 4000 and 6000 Hz when measured in-situ compared to headphones, which was attributed to differences in earmould vent sizes provided for different degrees of hearing loss at the low frequencies and probe placement in the high frequencies. Conclusion: Overall in-situ audiometry proved to be valid especially in individuals with symmetrical sensorineural hearing loss. Although there are statistically signifi cant differences, they are within clinically accepted standards. Furthermore, thresholds measured in ear canal SPL will be more comparable as any changes in hearing threshold levels in either of the measurements will be refl ected by an inverse change in measured ear canal SPL during REDD measurements.