Validating a phase-inversion procedure to assess the signal-to-noise ratios at the output of hearing aids with wide-dynamic-range compression

Abstract

Even for the same signal-to-noise ratio (SNR) at the input of a hearing aid, the output SNR may vary due to nonlinear compression algorithms. To quantify the output SNR of hearing aids, a phase-inversion technique is commonly used. The current study was designed to determine whether the phase-inversion technique accurately estimates the SNR for a simulated hearing aid. A simulated hearing aid was used to allow the explicit control of the compression algorithm and the calculation of the actual SNR at its output. The actual output SNRs were then used as the ground truth to evaluate the estimated output SNRs using the phase-inversion technique. Connected speech added to background noise (two- or twenty-talker babble), presented at SNRs of –10 to +10 dB, was used as test stimuli at the input of the simulated hearing aid. Four representative audiograms were used to set the gain and compression ratio for the simulated hearing aid according to a standard prescription method. In separate conditions, the hearing-aid compression was either fast- or slow-acting. Results showed that the estimated and actual output SNRs were not significantly different and their differences were within ±0.12 dB across all test conditions, indicating satisfactory agreement.