The goal of this study was to evaluate how digital noise reduction (DNR) impacts listening effort and judgment of sound clarity in children with normal hearing. It was hypothesized that when two DNR algorithms differing in signal-to-noise ratio (SNR) output are compared, the algorithm that provides the greatest improvement in overall output SNR will reduce listening effort and receive a better clarity rating from child listeners. A secondary goal was to evaluate the relation between the inversion method measurements and listening effort with DNR processing.
Twenty-four children with normal hearing (ages 7 to 12 years) participated in a speech recognition task in which consonant-vowel-consonant nonwords were presented in broadband background noise. Test stimuli were recorded through two hearing aids with DNR off and DNR on at 0 dB and +5 dB input SNR. Stimuli were presented to listeners and verbal response time (VRT) and phoneme recognition scores were measured. The underlying assumption was that an increase in VRT reflects an increase in listening effort. Children rated the sound clarity for each condition. The two commercially available HAs were chosen based on: (1) an inversion technique, which was used to quantify the magnitude of change in SNR with the activation of DNR, and (2) a measure of magnitude-squared coherence, which was used to ensure that DNR in both devices preserved the spectrum.
One device provided a greater improvement in overall output SNR than the other. Both DNR algorithms resulted in minimal spectral distortion as measured using coherence. For both devices, VRT decreased for the DNR-on condition, suggesting that listening effort decreased with DNR in both devices. Clarity ratings were also better in the DNR-on condition for both devices. The device showing the greatest improvement in output SNR with DNR engaged improved phoneme recognition scores. The magnitude of this improved phoneme recognition was not accurately predicted with measurements of output SNR. Measured output SNR varied in the ability to predict other outcomes.
Overall, results suggest that DNR effectively reduces listening effort and improves subjective clarity ratings in children with normal hearing but that these improvements are not necessarily related to the output SNR improvements or preserved speech spectra provided by the DNR.
This study evaluates how digital noise reduction (DNR) impacts listening effort and judgment of sound clarity, and evaluates the relation between the inversion method measurements and listening effort with DNR processing. Twenty-four normal-hearing children participated in a speech recognition task in which consonant-vowel-consonant nonwords were presented in background noise and processed through two hearing aids with DNR-off and DNR-on. Results revealed a significant improvement in phoneme recognition for one device with DNR-on and suggest that DNR reduces listening effort and improves subjective clarity ratings in children. These improvements are not related to inversion method measurements.
1Arizona State University, Phoenix, Arizona, USA; 2Boys Town National Research Hospital, Boys Town, Omaha, Nebraska, USA; 3Department of Hearing and Speech Sciences, Vanderbilt University, Nashville, Tennessee, USA.
This research was supported by National Institutes of Health grants RO1 DC4300 10, R03 DC009334, T35 DC8757, F31 DC010505, and P30 DC4662.
The authors declare no conflict of interest.
Address for correspondence: Samantha Gustafson, Department of Hearing and Speech Sciences, Vanderbilt Bill Wilkerson Center, 1215 21st Avenue South, Medical Center East, South Tower, Nashville, TN 37232, USA. E-mail: Samantha.Gustafson@Vanderbilt.edu