Objective Quantification of the Acoustic Parameters of Hearing Aid-processed Speech Stimuli

Background and Aim: The goal of the present study was to objectively quantify the changes in acoustic parameters of the speech signal by comparing the unprocessed and hearing aid-processed speech stimuli. Materials and Methods: Eight hearing aids from two manufacturing companies were programmed for four different conditions: (a) noise reduction “OFF” and directionality “OFF;” (b) noise reduction “ON” and directionality “OFF;” (c) noise reduction “OFF” and directionality “ON;” and (d) noise reduction “ON” and directionality “ON.” One consonant-vowel-consonant-vowel word from the low-frequency, midfrequency, and high-frequency range each was used as stimuli. A sound level meter was used to record the speech stimuli output from the Knowles Electronics Manikin for Acoustic Research routed through the hearing aid (processed) and without the hearing aid (unprocessed). The recorded stimuli were further acoustically analyzed using PRAAT software. Results: The mean pitch, jitter, shimmer, and noise-to-harmonic ratio values differed between the unprocessed and hearing aid-processed speech stimuli, especially for the low-frequency and midfrequency stimuli. Whereas, for the high-frequency stimulus, PRAAT software failed to provide any value for the above-mentioned acoustic features for hearing aid-processed stimulus. Discussions: The processed speech had perturbations and more noise irrespective of the frequency of the speech stimulus. Hence, the outcome of the current study highlights the necessity to assess hearing aid-processed acoustic stimuli to check for the hearing aid’s performance.