Comparing speech recognition for listeners with normal and impaired hearing: Simulations for controlling differences in speech levels and spectral shape

Purpose: This study investigated methods used to simulate factors associated with reduced audibility, increased speech levels, and spectral shaping for aided older adults with hearing loss. Simulations provided to younger normal-hearing adults were used to investigate the effect of sensation level, speech presentation level, and spectral shape in comparison to older adults with hearing loss. Method: Measures were assessed in quiet, steady-state noise, and speech-modulated noise. Older adults with hearing loss listened to speech that was spectrally shaped according to their hearing thresholds. Younger adults with normal hearing listened to speech that simulated the hearing-impaired group’s (a) reduced audibility, (b) increased speech levels, and (c) spectral shaping. Group comparisons were made based on speech recognition performance and masking release. Additionally, younger adults completed measures of listening effort and perceived speech quality to assess if differences across simulations in these outcome measures were similar to those for speech recognition. Results: Across the various simulations employed, testing in the presence of a threshold matching noise best matched differences in speech recognition and masking release between younger and older adults. This result remained consistent across the other two outcome measures. Conclusions: A combination of audibility, speech level, and spectral shape factors is required to simulate differences between listeners with normal and impaired hearing in recognition, listening effort, and perceived speech quality. The use of spectrally shaped and amplified speech in the presence of threshold matching noise best provided this simulated control.