Abnormal speech processing in frequency regions where absolute thresholds are normal for listeners with high-frequency hearing loss

Abnormal intelligibility of speech in competing speech and in noise in a frequency region where audiometric thresholds are near-normal for hearing-impaired listeners

“…In the latter condition, SRTs were poorer for the HI listeners than for the NH listeners by about 3 dB. Léger et al (2012b) measured consonant identification in quiet and in the presence of unmodulated, amplitude-modulated, and spectrally modulated speech-shaped noise at several signal-to-noise ratios for stimuli restricted to a low-frequency region (<1.5 kHz) for NH listeners and HI listeners with near-normal hearing (≤ 25 dB HL) in the tested low-frequency region. Consonant identification was poorer for the HI listeners than for the NH listeners in all conditions.…”

“…Over the last decade, a wealth of psychophysical and modeling studies have attempted to tease apart the contribution of reduced audibility and supra-threshold auditory deficits to the intelligibility speech in complex backgrounds for HI listeners (e.g., Bernstein and Grant, 2009; Christiansen and Dau, 2012; Léger et al, 2012b, 2012c; Rhebergen et al, 2006, 2010b; Strelcyk and Dau, 2009). In most studies, reduced audibility, as measured by audiometric hearing loss, was not sufficient to explain the poorer intelligibility of speech, especially in the presence of fluctuating noise or interfering speech (e.g., Bernstein and Grant, 2009; Hopkins and Moore, 2011; Lorenzi et al, 2006; Neher et al, 2012; Sheft et al, 2012; Summers and Molis, 2004; Summers et al, 2013).…”

“…Several studies (e.g., Horwitz et al, 2002; Léger et al, 2012b, 2012c; Lorenzi et al, 2009; Papakonstantinou et al, 2011; Strelcyk and Dau, 2009) have shown mild-to-severe speech identification deficits for HI listeners using stimuli filtered into a low-frequency region (lower than 1-3 kHz) where audiometric thresholds were classified as normal (lower than 20 dB HL) or near-normal (lower than 25-30 dB HL) according to audiological conventions (i.e., ANSI, 1996). …”

Effects of steep high-frequency hearing loss on speech recognition using temporal fine structure in low-frequency region

“…Decreased audibility provides at least part of the explanation. However, there is increasing evidence that suprathreshold processing deficits may also contribute to the speech perception problem (Feng et al, 2010;Horwitz et al, 2002;Leger et al, 2012;Lorenzi et al, 2009;Yin et al, 2008). This is supported by the fact that individuals whose auditory sensitivity is restored via hearing-aid amplification still show speech perception problems (Kerber and Seeber, 2012;Stephens et al, 1996).…”

“…Thus, recognition performance may reflect solely the contribution of supra-threshold auditory processing skills. Results from previous studies demonstrate that there are indeed supra-threshold processing deficits in the frequency region where the absolute thresholds were within normal, as shown by poorer-than-normal temporal, frequency, and intensity discrimination thresholds (Florentine et al, 1993;Leger et al, 2012;Lorenzi et al, 2009;Nelson and Freyman, 1986;Schroder et al, 1994;Simon and Yund, 1993). However, most of these studies used signals synthesized from non-linguistic sounds, such as tone or noise, and the relationship between these psychoacoustic measurements and speech perception remains unclear.…”