Independent impacts of age and hearing loss on spatial release in a complex auditory environment

Abstract

Listeners in complex auditory environments can benefit from the ability to use a variety of spatial and spectrotemporal cues for sound source segregation. Probing these abilities is an essential part of gaining a more complete understanding of why listeners differ in navigating the auditory environment. Two fundamental processes that can impact the auditory systems of individual listeners are aging and hearing loss. One difficulty with uncovering the independent effects of age and hearing loss on spatial release is the commonly observed phenomenon of age-related hearing loss. In order to reveal the effects of aging on spatial hearing, it is essential to develop testing methods that reduce the influence of hearing loss on the outcomes. The statistical power needed for such testing generally requires a larger number of participants than can easily be tested using traditional behavioral methods. This work describes the development and validation of a rapid method by which listeners can be categorized in terms of their ability to use spatial and spectrotemporal cues to separate competing speech streams. Results show that when age and audibility are not covarying, age alone can be shown to substantially reduce spatial release from masking. These data support the hypothesis that aging, independent of an individual's hearing threshold, can result in changes in the cortical and/or subcortical structures essential for spatial hearing.

Release from masking for small spatial separations: Effects of age and hearing loss

“…However, the researchers did not examine release at smaller separations than 15 , or with older or HI listeners. One reason to examine the effects of small separations in older listeners in particular, is that Gallun et al (2013) showed that older individuals often achieve less SRM than younger individuals, regardless of hearing status. F€ ullgrabe et al (2015) concluded that reductions in SRM could be attributed to cognitive changes related to aging rather than age-related loss of binaural senstivity per se.…”

Physiology, Psychoacoustics and Cognition in Normal and Impaired Hearing

“…The level of each component was adjusted based on the difference between the audiogram of the listener being tested and the audiogram of a comparison listener with 0 dB HL thresholds at each of the six octave frequencies, and then the six waveforms were summed. To estimate thresholds, the levels of the two masking sentences were adjusted relative to the level of the target sentence according to a progressive tracking algorithm which has been shown to be comparable to and more efficient than adaptive tracking (Gallun et al 2013).…”

“…Head-related transfer functions (HRTFs) were used to position the target sentences at 0° azimuth and the maskers either colocated with the target or at ± 45° (Gallun et al 2013;Xie 2013). In the first experiment the target sentences were fixed at either 19.5 dB SL (low SL condition) or 39.5 dB SL (high SL condition) above each participant's speech reception threshold (SRT) in quiet.…”

“…This paper describes related studies from three different laboratories that used the "symmetric masker" configuration to explore the interaction between target audibility and performance under these conditions. Gallun et al (2013) found that the effect of hearing loss on separated thresholds was stronger when one target level was used for all listeners (50 dB SPL) compared to when a sensation level (SL) of 40 dB was used (equivalent to a range of 47-72 dB SPL). They speculated that a broadband increase in gain was not sufficient to combat the non-flat hearing losses of their subjects.…”

Probing auditory scene analysis

“…Gallun et al (2013) demonstrated that listeners could be categorized in terms of their ability to use spatial and spectrotemporal cues to separate competing speech streams. They showed that the factor of age substantially reduced spatial release from masking, supporting the hypothesis that aging, independent of an individual's hearing threshold, can result in changes in the cortical and/or subcortical structures essential for spatial hearing.…”