Contribution of high frequencies to speech recognition in quiet and noise in listeners with varying degrees of high-frequency sensorineural hearing loss

Purpose: The contribution of audible high-frequency information to speech-understanding performance in listeners with varying degrees of high-frequency sensorineural hearing loss was examined. Method: Thirty-six elderly hearing-impaired (EHI) and 24 young normal-kearing (YNH) listeners were tested in quiet (+20 dB speech-to-noise ratio [SNR]) and noise (+5 dB SNR) and under different bandpass conditions (narrow, 200-1600 Hz; midband, 200-3200 Hz; broadband, 200-6400 Hz), both without and with spectral shaping of the stimuli. Monosyllabic word-recognition performance was examined through use of both whole-word scoring and phoneme scoring. The 36 EHI listeners were divided into 3 groups of 12 listeners each, with the groups differing in the amount of high-frequency hearing loss. The 24 YNH participants were separated into 2 groups, each serving as a reference group for either the unshaped or spectrally shaped speech listening conditions. Results: Results for spectrally shaped speech, in both quiet and noise, revealed that the 3 EHI groups performed equivalently in the different bandwidth conditions and demonstrated no change (increase or decrease) in word-recognition performance between the midband and broadband conditions. The YNH groups, however, demonstrated improved speech understanding attributable to the higher frequencies for the broadband condition in both the unshaped and shaped conditions. Conclusions: Data from the EHI listeners revealed that performance for unshaped speech was correlated moderately and negatively with degree of high-frequency hearing loss. Alternatively, recognition performance for shaped speech was related to neither the performance for unshaped speech nor the amount of high-frequency hearing loss.