Estimating audiometric thresholds using simultaneous acquisition of ASSR and ABR from QASSR in patients with sensorineural hearing loss

Objectives: To evaluate the accuracy with which the innovative QASSR method predicts behavioral thresholds in adult patients with sensorineural hearing loss. Design: Subjects were tested at four carrier frequencies (500, 1000, 2000, and 4000 Hz).The resulting QASSR recordings were analyzed for thresholds and magnitude/phase characteristics. Tone-burst ABR was recovered from QASSR signal using CLAD method and analyzed in the time domain. The electrophysiological estimates were compared to hearing thresholds determined behaviorally. Study sample: Sixteen ears of nine volunteer subjects recruited from a clinical population. Results: All mean threshold estimates differed less than 3 dB for QASSR and less than 5 dB for ABR at 1000, 2000 and 4000Hz (carrier or pure-tone test frequencies). The largest differences were observed for both at 500 Hz (5.63 and 11.56 dB respectively).The audiometric configurations of QASSR and ABR estimates followed those of the respective behaviorally determined configurations across ears tested. Conclusions: QASSR method merges two dissimilar stimulation techniques, transient and steady-state, to create a hybrid stimulation-and-analysis paradigm that seems to improve the overall performance of the electrophysiological threshold estimation. The unique feature of the QASSR technique is the additional information afforded by the transient ABR, recovered from the same recording. The QASSR thus holds promise to be a very useful tool for practical clinical applications

Reference hearing threshold levels for chirp signals delivered by an ER-3A insert earphone

Objective: To establish reference hearing threshold levels for chirps and frequency-specific chirps. Design: Hearing thresholds were determined monaurally for broad-band chirps and octave-band chirps using the Etymotic Research, ER-3A insert earphone. The chirps were presented using two repetition rates, 20 and 90 stimuli/s, and with alternating polarity in blocks of one second duration. The test procedure and test conditions were in accordance with the recommendations given in ISO 389-9 (2009). The ascending method (ISO 8253-1, 2010) was applied using a step size of 5 dB. The chirps were played back from a Tucker Davies Technologies System II, and a Matlab program controlled the test setup. The results are specified in dB peak-to-peak equivalent threshold sound pressure levels (dB peETSPL). Study sample: The test group consisted of 25 otologically-normal young adults (age 18–25 years). Results: The results are in good agreement with the results from another investigation of hearing thresholds using the same chirp stimuli, and the values for the octave-band chirps are in line with the standardized reference values for corresponding tone bursts (ISO 389-6, 2007). Conclusions: The results of the present investigation are relevant for the international standard on short duration signals, ISO 389-6 (2007)