Foundations of modern auditory theory

https://cyberleninka.org/article/n/1334253.pdf

Communication masking in marine mammals: A review and research strategy.

Objectives A common complaint of many older adults is difficulty communicating in situations where they must focus on one talker in the presence of other people speaking. In listening environments containing multiple talkers, age-related changes may be caused by increased sensitivity to energetic masking, increased susceptibility to informational masking (e.g., confusion between the target voice and masking voices), and/or cognitive deficits. The purpose of the present study was to tease out these contributions to the difficulties that older adults experience in speech-on-speech masking situations. Design Groups of younger, normal-hearing individuals and older adults with varying degrees of hearing sensitivity (n = 12 per group) participated in a study of sentence recognition in the presence of four types of maskers: a two-talker masker consisting of voices of the same sex as the target voice, a two-talker masker of voices of the opposite sex as the target, a signal-envelope-modulated noise derived from the two-talker complex, and a speech-shaped steady noise. Subjects also completed a voice discrimination task to determine the extent to which they were able to incidentally learn to tell apart the target voice from the same-sex masking voices and to examine whether this ability influenced speech-on-speech masking. Results Results showed that older adults had significantly poorer performance in the presence of all four types of maskers, with the largest absolute difference for the same-sex masking condition. When the data were analyzed in terms of relative group differences (i.e., adjusting for absolute performance) the greatest effect was found for the opposite-sex masker. Degree of hearing loss was significantly related to performance in several listening conditions. Some older subjects demonstrated a reduced ability to discriminate between the masking and target voices; performance on this task was not related to speech recognition ability. Conclusions The overall pattern of results suggests that although amount of informational masking does not seem to differ between older and younger listeners, older adults (particularly those with hearing loss) evidence a deficit in the ability to selectively attend to a target voice, even when the masking voices are from talkers of the opposite sex. Possible explanations for these findings include problems understanding speech in the presence of a masker with temporal and spectral fluctuations and/or age-related changes in cognitive function.

/pdf/aging-and-speech-on-speech-masking-39vjva69we.pdf

Aging and speech-on-speech masking.

Previous studies have demonstrated that lung volume during wakefulness influences upper airway size and resistance, particularly in patients with sleep apnea. We sought to determine the influence of lung volume on the level of continuous positive airway pressure (CPAP) required to prevent flow limitation during non-REM sleep in subjects with sleep apnea. Seventeen subjects (apnea–hypopnea index, 42.6 ± 6.2 [SEM]) were studied during stable non-REM sleep in a rigid head-out shell equipped with a positive/negative pressure attachment for manipulation of extrathoracic pressure. An epiglottic pressure catheter plus a mask/pneumotachometer were used to assess flow limitation. When lung volume was increased by 1,035 ± 22 ml, the CPAP level could be decreased from 11.9 ± 0.7 to 4.8 ± 0.7 cm H2O (p < 0.001) without flow limitation. The decreased CPAP at the same negative extrathoracic pressure yielded a final lung volume increase of 421 ± 36 ml above the initial value. Conversely, when lung volume was reduced by ...

Lung volume and continuous positive airway pressure requirements in obstructive sleep apnea

Binaural room impulse responses (BRIRs) were measured in a classroom for sources at different azimuths and distances (up to 1 m) relative to a manikin located in four positions in a classroom. When the listener is far from all walls, reverberant energy distorts signal magnitude and phase independently at each frequency, altering monaural spectral cues, interaural phase differences, and interaural level differences. For the tested conditions, systematic distortion (comb-filtering) from an early intense reflection is only evident when a listener is very close to a wall, and then only in the ear facing the wall. Especially for a nearby source, interaural cues grow less reliable with increasing source laterality and monaural spectral cues are less reliable in the ear farther from the sound source. Reverberation reduces the magnitude of interaural level differences at all frequencies; however, the direct-sound interaural time difference can still be recovered from the BRIRs measured in these experiments. Results suggest that bias and variability in sound localization behavior may vary systematically with listener location in a room as well as source location relative to the listener, even for nearby sources where there is relatively little reverberant energy.

Localizing nearby sound sources in a classroom: binaural room impulse responses.

The smallest detectable interaural time difference (ITD) for sine tones was measured for four human listeners to determine the dependence on tone frequency. At low frequencies, 250–700 Hz, threshold ITDs were approximately inversely proportional to tone frequency. At mid-frequencies, 700–1000 Hz, threshold ITDs were smallest. At high frequencies, above 1000 Hz, thresholds increased faster than exponentially with increasing frequency becoming unmeasurably high just above 1400 Hz. A model for ITD detection began with a biophysically based computational model for a medial superior olive (MSO) neuron that produced robust ITD responses up to 1000 Hz, and demonstrated a dramatic reduction in ITD-dependence from 1000 to 1500 Hz. Rate-ITD functions from the MSO model became inputs to binaural display models—both place based and rate-difference based. A place-based, centroid model with a rigid internal threshold reproduced almost all features of the human data. A signal-detection version of this model reproduced the high-frequency divergence but badly underestimated low-frequency thresholds. A rate-difference model incorporating fast contralateral inhibition reproduced the major features of the human threshold data except for the divergence. A combined, hybrid model could reproduce all the threshold data.

/pdf/human-interaural-time-difference-thresholds-for-sine-tones-4fsy22u1zy.pdf

Human interaural time difference thresholds for sine tones: the high-frequency limit

We present a simple and reliable method to calibrate respiratory magnetometers and Respitrace to infer respiratory volume changes. As in earlier methods, we assume two degrees of freedom in the che...

A simple and reliable method to calibrate respiratory magnetometers and Respitrace

Summary Arbogast et al. [1] found a large release from masking obtained by the spatial separation of a target talker and a competing speech masker. Both signal and masker were sentences from the Coordinate Response Measure corpus processed by extracting the envelopes of 15 narrow frequency bands and using the envelopes to modulate carrier tones at the center of each band. By playing nonoverlapping subsets (6–8) of bands from the signal and masker, the energetic component of masking was minimized while the informational component was maximized. The current study extended that work to determine the interaction between reverberation, masker type and spatial release from masking. The stimuli were processed in the same way and were presented in the same spatial configuration as the earlier study. The target sentence was presented at 0-deg azimuth while the masker sentence was played at either 0- or 90-deg azimuth. Noise-masker controls, comprised of overlapping or nonoverlapping frequency bands, were also tested. The listening environment was an IAC booth having interior dimensions of 12’4” 13’ 7’6”. Acoustic extremes were achieved by covering all surfaces with materials that were either highly reflective (Plexiglas panels) or highly absorbent of sound (Silent Source foam wedges). The results indicated that the amount of masking and the spatial release from masking depended both on the characteristics of the room and the masker type. When the masker was primarily energetic, spatial release from masking decreased from a maximum of about 8dB in the least reverberant room to about 2dB in the most reverberant room. For the informational masker, a larger advantage of 15–17dB was found that was not affected by reverberation. Our interpretation of these findings was that spatial separation of sources could improve speech identification through acoustic filtering by the head, binaural interaction, and the strengthening of perceptual segregation of sound images. However, only the latter effect appears to be relatively insensitive to reverberation.

/pdf/the-role-of-reverberation-in-release-from-masking-due-to-4ftuxcpw9c.pdf

The role of reverberation in release from masking due to spatial separation of sources for speech identification

A simple, biophysically specified cell model is used to predict responses of binaurally sensitive neurons to patterns of input spikes that represent stimulation by acoustic and electric waveforms. Specifically, the effects of changes in parameters of input spike trains on model responses to interaural time difference (ITD) were studied for low-frequency periodic stimuli, with or without amplitude modulation. Simulations were limited to purely excitatory, bilaterally driven cell models with basic ionic currents and multiple input fibers. Parameters explored include average firing rate, synchrony index, modulation frequency, and latency dispersion of the input trains as well as the excitatory conductance and time constant of individual synapses in the cell model. Results are compared to physiological recordings from the inferior colliculus (IC) and discussed in terms of ITD-discrimination abilities of listeners with cochlear implants. Several empirically observed aspects of ITD sensitivity were simulated without evoking complex neural processing. Specifically, our results show saturation effects in rate–ITD curves, the absence of sustained responses to high-rate unmodulated pulse trains, the renewal of sensitivity to ITD in high-rate trains when inputs are amplitude-modulated, and interactions between envelope and fine-structure delays for some modulation frequencies.

/pdf/models-of-brainstem-responses-to-bilateral-electrical-2df7q1t79g.pdf

Models of Brainstem Responses to Bilateral Electrical Stimulation

Many past studies of sound localization explored the precedence effect (PE), in which a pair of brief, temporally close sounds from different directions is perceived as coming from a location near that of the first-arriving sound. Here, a computational model of low-frequency inferior colliculus (IC) neurons accounts for both physiological and psychophysical responses to PE click stimuli. In the model, IC neurons have physiologically plausible inputs, receiving excitation from the ipsilateral medial superior olive (MSO) and long-lasting inhibition from both ipsilateral and contralateral MSOs, relayed through the dorsal nucleus of the lateral lemniscus. In this model, physiological suppression of the lagging response depends on the inter-stimulus delay (ISD) between the lead and lag as well as their relative locations. Psychophysical predictions are generated from a population of model neurons. At all ISDs, predicted lead localization is good. At short ISDs, the estimated location of the lag is near that of the lead, consistent with subjects perceiving both lead and lag from the lead location. As ISD increases, the estimated lag location moves closer to the true lag location, consistent with listeners’ perception of two sounds from separate locations. Together, these simulations suggest that location-dependent suppression in IC neurons can explain the behavioral phenomenon known as the precedence effect.

/pdf/physiological-and-psychophysical-modeling-of-the-precedence-3g1zkybl6q.pdf

Andrew Brughera

Papers

Human interaural time difference thresholds for sine tones: the high-frequency limit

A simple and reliable method to calibrate respiratory magnetometers and Respitrace

The role of reverberation in release from masking due to spatial separation of sources for speech identification

Models of Brainstem Responses to Bilateral Electrical Stimulation

Physiological and psychophysical modeling of the precedence effect.