Effects of sound-induced hearing loss and hearing AIDS on the perception of music

This is the final version of the article. It first appeared from the Audio Engineering Society via https://doi.org/10.17743/jaes.2015.0081Exposure to high-level music produces several physiological changes in the auditory system that lead to a variety of perceptual effects. Damage to the outer hair cells within the cochlea leads to a loss of sensitivity to weak sounds, loudness recruitment (a more rapid than normal growth of loudness with increasing sound level) and reduced frequency selectivity. Damage to inner hair cells and/or synapses leads to degeneration of neurons in the auditory nerve and to a reduced flow of information to the brain. This leads to poorer auditory discrimination and may contribute to reduced sensitivity to the temporal fine structure of sounds and to poor pitch perception. Hearing aids compensate for the effects of threshold elevation and loudness recruitment via multi-channel amplitude compression, but they do not compensate for reduced frequency selectivity or loss of inner hair cells/synapses/neurons. Multi-channel compression can impair some aspects of the perception of music, such as the ability to hear out one instrument or voice from a mixture. The limited frequency range and irregular frequency response of most hearing aids is associated with poor sound quality for music. Finally, systems for reducing acoustic feedback can have undesirable side effects when listening to music.This work was supported by the Medical Research Council (UK, grant number G0701870), Action on Hearing Loss, Phonak, and Starkey

Missing a Trick: Auditory Load Modulates Conscious Awareness in Audition

In the visual domain there is considerable evidence supporting the Load Theory of Attention and Cognitive Control, which holds that conscious perception of background stimuli depends on the level of perceptual load involved in a primary task. However, literature on the applicability of this theory to the auditory domain is limited and, in many cases, inconsistent. Here we present a novel “auditory search task” that allows systematic investigation of the impact of auditory load on auditory conscious perception. An array of simultaneous, spatially separated sounds was presented to participants. On half the trials, a critical stimulus was presented concurrently with the array. Participants were asked to detect which of 2 possible targets was present in the array (primary task), and whether the critical stimulus was present or absent (secondary task). Increasing the auditory load of the primary task (raising the number of sounds in the array) consistently reduced the ability to detect the critical stimulus. This indicates that, at least in certain situations, load theory applies in the auditory domain. The implications of this finding are discussed both with respect to our understanding of typical audition and for populations with altered auditory processing. (PsycINFO Database Record (c) 2016 APA, all rights reserved

Loudness of ramped and damped sounds that are temporally shifted across ears

© 2019 Proceedings of the International Congress on Acoustics. All rights reserved. In a previous study we have shown that amplitude-modulated sounds are louder when their modulation is out of phase across the two ears than when it is in phase. The level difference required for equal loudness (LDEL) of sounds with diotic presentation and an interaural modulation phase difference of 180° was about 2 dB. This could be explained by a loudness model where binaural summation lags behind binaural inhibition. The present study investigated the binaural loudness of ramped and damped sounds in a similar manner. Stimuli consisted of trains of 1000-Hz tone pulses with linear rise and fall times with ratios of 1:10 (damped sounds) or 10:1 (ramped sounds). Stimuli contained 28 55-ms pulses, 14 110-ms pulses or 7 220-ms pulses, resulting in a stimulus duration of 1540 ms plus half the pulse duration for the interaurally shifted stimuli. The LDEL between diotic and interaurally shifted stimuli was close to 0 dB for all of these conditions. For a single 220-ms pulse, the LDEL was 1.4 dB for damped sounds, and 3.0 dB for ramped sounds, the diotic sounds being louder. The difference between a single pulse and a pulse train suggests differences between short-term and long-term loudness judgments.EPSR

Estimation of auditory filter shapes across frequencies using machine learning

When fitting a hearing aid, the level-dependent gain prescribed at each frequency is usually based on the hearing loss at that frequency. This often results in reasonable fittings for a typical cochlear hearing loss, but may fail when the individual frequency selectivity and/or loudness growth are different from what would be typical for that hearing loss. Individualised fitting based on measures of frequency selectivity might be useful in improving a fitting, for example by reducing across-channel masking. A popular measure of frequency selectivity is the notched-noise method, but this test is time-consuming. To reduce testing time, Shen and Richards (2013) proposed an efficient machine-learning test that determines the slope of the skirts of the auditory filter (p), its minimum response for wide notches (r), and detection efficiency (K). However, their test did not determine asymmetries in the auditory filter, which are important to consider during fitting to reduce across-channel masking. The test proposed here provides a time-efficient way of estimating the auditory filter shape and asymmetry as a function of center frequency. The noise level required for threshold is estimated for a tone with frequency fs presented at 15 dB SL in nine symmetric or asymmetric notched noises with notch edge frequencies between 0.6 and 1.4 fs. Using only narrow to medium notch widths provides good information about the tip of the auditory filter, which is of most importance in determining across-channel masking for speech-like signals (but the tail is not well defined). The nine thresholds for a given fs can be used to fit an auditory filter model with three parameters: the slopes of the lower and upper sides (pl, pu) and K. In practice, these model parameters are estimated as a continuous function of fs, and fs is varied across trials over the range 0.5-4 kHz. The stimulus parameters on a given trial (fs, notch condition, noise level) are chosen to maximally reduce the uncertainty in the model parameters, exploiting the covariance between thresholds for adjacent values of fs. Six subjects have been tested so far. The whole procedure took about 45 minutes per ear. The lower slopes typically corresponded with values expected from the audiogram and a cochlear hearing loss. The upper slopes were steeper in some cases, although not necessarily across the whole frequency range. Reference Shen, Y., and Richards, V. M. (2013). "Bayesian adaptive estimation of the auditory filter," J. Acoust. Soc. Am. 134, 1134-1145.EPSR

The lower limit of pitch perception for pure tones and low-frequency complex sounds

The lower limit of pitch (LLP) perception was explored for pure tones, sinusoidally amplitude-modulated (SAM) tones with a carrier frequency of 125 Hz, and trains of 125-Hz tone pips, using an adaptive procedure to estimate the lowest repetition rate for which a tonal/humming quality was heard. The LLP was similar for the three stimulus types, averaging 19 Hz. There were marked individual differences, which were correlated to some extent across stimulus types. The pure-tone stimuli contained a single resolved harmonic, whereas the SAM tones and tone-pip trains contained only unresolved components, whose frequencies did not necessarily form a harmonic series. The similarity of the LLP across stimulus types suggests that the LLP is determined by the repetition period of the sound for pure tones, and the envelope repetition period for complex stimuli. The results are consistent with the idea that the LLP is determined by a periodicity analysis in the auditory system, and that the longest time interval between waveform or envelope peaks for which this analysis can be performed is approximately 53 ms

Auditory spatial representations of the world are compressed in blind humans

Compared to sighted listeners, blind listeners often display enhanced auditory spatial abilities such as localization in azimuth. However, less is known about whether blind humans can accurately judge distance in extrapersonal space using auditory cues alone. Using virtualization techniques, we show that auditory spatial representations of the world beyond the peripersonal space of blind listeners are compressed compared to those for normally sighted controls. Blind participants overestimated the distance to nearby sources and underestimated the distance to remote sound sources, in both reverberant and anechoic environments, and for speech, music, and noise signals. Functions relating judged and actual virtual distance were well fitted by compressive power functions, indicating that the absence of visual information regarding the distance of sound sources may prevent accurate calibration of the distance information provided by auditory signals.This research was supported by MRC Grant G0701870 and the Vision and Eye Research Unit (VERU), Postgraduate Medical Institute at Anglia Ruskin University

Discrimination of amplitude-modulation depth by subjects with normal and impaired hearing

The loudness recruitment associated with cochlear hearing loss increases the perceived amount of amplitude modulation (AM), called "fluctuation strength." For normal-hearing (NH) subjects, fluctuation strength "saturates" when the AM depth is high. If such saturation occurs for hearing-impaired (HI) subjects, they may show poorer AM depth discrimination than NH subjects when the reference AM depth is high. To test this hypothesis, AM depth discrimination of a 4-kHz sinusoidal carrier, modulated at a rate of 4 or 16 Hz, was measured in a two-alternative forced-choice task for reference modulation depths, $\textit{m}$$_{ref}$, of 0.5, 0.6, and 0.7. AM detection was assessed using $\textit{m}$$_{ref}$= 0. Ten older HI subjects, and five young and five older NH subjects were tested. Psychometric functions were measured using five target modulation depths for each $\textit{m}$$_{ref}$. For AM depth discrimination, the HI subjects performed more poorly than the NH subjects, both at 30 dB sensation level (SL) and 75 dB sound pressure level (SPL). However, for AM detection, the HI subjects performed better than the NH subjects at 30 dB SL; there was no significant difference between the HI and NH groups at 75 dB SPL. The results for the NH subjects were not affected by age.This work was supported by the Engineering and Physical Sciences Research Council (UK, Grant No. RG78536)

Envelope regularity discrimination

© 2019 Acoustical Society of America. The ability to discriminate irregular from regular amplitude modulation was assessed using the "envelope regularity discrimination" test. The amount of irregularity was parametrically varied and quantified by an "irregularity index." Normative data were gathered for young subjects with normal audiometric thresholds. Parameters varied were the carrier and modulation frequencies, f c and f m , and the baseline modulation index, m. All tests were performed using a background threshold-equalizing noise. The main findings were (1) using f c = 4000 Hz, f m = 8 Hz, and m = 0.3, performance improved over the first two threshold runs and then remained roughly stable, and there was a high correlation between thresholds obtained at 80 dB sound pressure level (SPL) and at 20 dB sensation level; (2) using f m = 8 Hz and m = 0.3 with a level of 80 dB SPL, thresholds did not vary significantly across f c = 1000, 2000, and 4000 Hz; (3) using f m = 8 Hz and f c = 4000 Hz with a level of 80 dB SPL, thresholds did not vary significantly for m from 0.2 to 0.5; and (4) using m = 0.3 and f c = 4000 Hz with a level of 80 dB SPL, thresholds improved with increasing f m from 2 to 16 Hz. For all conditions, there was substantial individual variability, probably resulting from differences in "processing efficiency.