Temporal Effects on Monaural Amplitude-Modulation Sensitivity in Ipsilateral, Contralateral and Bilateral Noise

Abstract

The amplitude modulations (AMs) in speech signals are useful cues for speech recognition. Several adaptation mechanisms may make the detection of AM in noisy backgrounds easier when the AM carrier is presented later rather than earlier in the noise. The aim of the present study was to characterize temporal adaptation to noise in AM detection. AM detection thresholds were measured for monaural (50 ms, 1.5 kHz) pure-tone carriers presented at the onset ('early' condition) and 300 ms after the onset ('late' condition) of ipsilateral, contralateral, and bilateral (diotic) broadband noise, as well as in quiet. Thresholds were 2-4 dB better in the late than in the early condition for the three noise lateralities. The temporal effect held for carriers at equal sensation levels, confirming that it was not due to overshoot on carrier audibility. The temporal effect was larger for broadband than for low-band contralateral noises. Many aspects in the results were consistent with the noise activating the medial olivocochlear reflex (MOCR) and enhancing AM depth in the peripheral auditory response. Other aspects, however, indicate that central masking and adaptation unrelated to the MOCR also affect both carrier-tone and AM detection and are involved in the temporal effects.

Correlation and Reliability of Behavioral and Otoacoustic-Emission Estimates of Contralateral Medial Olivocochlear Reflex Strength in Humans

“… Smith et al (2000) demonstrated that, in macaques, the tone threshold increment with CAS remained to some extent when MOC efferents were sectioned. Marrufo-Pérez et al (2018) showed that detection thresholds for short (50 ms) tones increased more when the tone and CAS onset coincided (early condition) than when the tone onset was delayed 300 ms from the CAS onset (late condition). Because the time course of MOCR activation is around 300 ms ( Backus and Guinan, 2006 ), one would expect greater threshold increments in the ‘late’ than in the ‘early’ condition if the MOCR were the only responsible for the increments, but this was not the case.…”

Optimizing Speech Recognition Using a Computational Model of Human Hearing: Effect of Noise Type and Efferent Time Constants

“…It has been suggested that different efferent time constants may be required in different listening situations [27]. A number of studies suggest that efferent activation may play a role in the perception of amplitude modulation in general [47] and in human speech perception [48], [49], although the effect of different background noise-type and time constants has not been explicitly assessed. Recent studies with a binaural cochlear implant sound coding strategy with efferent-inspired feedback also demonstrate improved speech intelligibility in noise with very short efferent time constants [50].…”

Olivocochlear efferent contributions to speech-in-noise recognition across signal-to-noise ratios

“…Marrufo-P erez et al (2018a) discussed that such an effect could allow the basilar membrane to follow the dips and peaks in amplitude-modulated waveforms and improve encoding of such signals (see Fig. 1A in Marrufo-P erez et al, 2018a). Modulations in the waveform of speech carry important information on place, manner, and voicing (Rosen, 1992).…”

“…The human auditory system contains a rich efferent network wherein the cortex modulates brainstem activity, and the brainstem influences cochlear activity. The auditory efferent system improves detection of sounds in background noise, reduces auditory damage due to high-intensity sound exposure, and may be involved in selective attention (for recent reviews, see Guinan, 2018;Lopez-Poveda, 2018). The medial olivocochlear (MOC) branch of the auditory efferent system innervates the outer hair cells (OHCs), which are responsible for cochlear amplification (for a review of cochlear amplification, see Ashmore, 2008).…”

“…For example, intensity discrimination is involved in the perception of stop consonants and vowel formants (Sinnott et al, 1985). Additionally, the MOCR may aid in encoding amplitude modulation at the level of the basilar membrane (Marrufo-P erez et al, 2018a), which can benefit perception of the different temporal components of the speech waveform (Rosen, 1992).…”