Detection Of Gaps In Noise Research Articles

Estimated Prevalence of Functional Hearing Difficulties in Blast-Exposed Service Members With Normal to Near-Normal-Hearing Thresholds.

Over the past decade, U.S. Department of Defense and Veterans Affairs audiologists have reported large numbers of relatively young adult patients who have normal to near-normal audiometric thresholds but who report difficulty understanding speech in noisy environments. Many of these service members also reported having experienced exposure to explosive blasts as part of their military service. Recent studies suggest that some blast-exposed patients with normal to near-normal-hearing thresholds not only have an awareness of increased hearing difficulties, but also poor performance on various auditory tasks (sound source localization, speech recognition in noise, binaural integration, gap detection in noise, etc.). The purpose of this study was to determine the prevalence of functional hearing and communication deficits (FHCD) among healthy Active-Duty service men and women with normal to near-normal audiometric thresholds. To estimate the prevalence of such FHCD in the overall military population, performance of roughly 3400 Active-Duty service members with hearing thresholds mostly within the normal range were measured on 4 hearing tests and a brief 6-question survey to assess FHCD. Subjects were subdivided into 6 groups depending on the severity of the blast exposure (3 levels: none, far away, or close enough to feel heat or pressure) and hearing thresholds (2 levels: audiometric thresholds of 20 dB HL or better, slight elevation in 1 or more thresholds between 500 and 4000 Hz in either ear). While the probability of having hearing difficulty was low (≈4.2%) for the overall population tested, that probability increased by 2 to 3 times if the service member was blast-exposed from a close distance or had slightly elevated hearing thresholds (>20 dB HL). Service members having both blast exposure and mildly elevated hearing thresholds exhibited up to 4 times higher risk for performing abnormally on auditory tasks and more than 5 times higher risk for reporting abnormally low ratings on the subjective questionnaire, compared with service members with no history of blast exposure and audiometric thresholds ≤20 dB HL. Blast-exposed listeners were roughly 2.5 times more likely to experience subjective or objective hearing deficits than those with no-blast history. These elevated rates of abnormal performance suggest that roughly 33.6% of Active-Duty service members (or approximately 423,000) with normal to near-normal-hearing thresholds (i.e., H1 profile) are at some risk for FHCD, and about 5.7% (approximately 72,000) are at high risk, but are currently untested and undetected within the current fitness-for-duty standards. Service members identified as "at risk" for FHCD according to the metrics used in the present study, in spite of their excellent hearing thresholds, require further testing to determine whether they have sustained damage to peripheral and early-stage auditory processing (bottom-up processing), damage to cognitive processes for speech (top-down processing), or both. Understanding the extent of damage due to noise and blast exposures and the balance between bottom-up processing deficits and top-down deficits will likely lead to better therapeutic strategies.

Psychoacoustic and Demographic Factors for Speech Recognition of Older Adult Cochlear Implant Users.

Purpose This study aimed to evaluate the effects of aging and cochlear implant (CI) on psychoacoustic and speech recognition abilities and to assess the relative contributions of psychoacoustic and demographic factors to speech recognition of older CI (OCI) users. Method Twelve OCI users, 12 older acoustic-hearing (OAH) listeners age-matched to OCI users, and 12 younger normal-hearing (YNH) listeners underwent tests of temporal amplitude modulation detection, temporal gap detection in noise, and spectral-temporal modulated ripple discrimination. Speech reception thresholds were measured for sentence recognition in multitalker, speech-babble noise. Results Statistical analyses showed that, for the small sample of OAH listeners, the degree of hearing loss did not significantly affect any outcome measure. Temporal resolution, spectral resolution, and speech recognition all significantly degraded with both age and the use of a CI (i.e., YNH better than OAH and OAH better than OCI performance). Although both were significantly correlated with OCI users' speech recognition, the duration of CI use no longer had a significant effect on speech recognition once the effect of spectral-temporal ripple discrimination performance was taken into account. For OAH listeners, the only significant predictor of speech recognition was temporal gap detection performance. Conclusion The preliminary results suggest that speech recognition of OCI users may improve with longer duration of CI use, mainly due to higher perceptual acuity to spectral-temporal modulated ripples in acoustic stimuli.

Speech Perception and Gap Detection Performance of Single-Sided Deafness under Noisy Conditions

Background and ObjectivesMany studies have reported no benefit of sound localization, but improved speech understanding in noise after treating patients with single-sided deafness (SSD). Furthermore, their performances provided a large individual difference. The present study aimed to measure the ability of speech perception and gap detection in noise for the SSD patients to better understand their hearing nature.Subjects and MethodsNine SSD patients with different onset and period of hearing deprivation and 20 young adults with normal hearing and simulated conductive hearing loss as the control groups conducted speech perception in noise (SPIN) and Gap-In-Noise (GIN) tests. The SPIN test asked how many presented sentences were understood at the +5 and -5 dB signal-to-noise ratio. The GIN test was asked to find the shortest gap in white noise with different lengths in the gap.ResultsCompared to the groups with normal hearing and simulated instant hearing loss, the SSD group showed much poor performance in both SPIN and GIN tests while supporting central auditory plasticity of the SSD patients. Rather than a longer period of deafness, the large individual variance indicated that the congenital SSD patients showed better performance than the acquired SSD patients in two measurements.ConclusionsThe results suggested that comprehensive assessments should be implemented before any treatment of the SSD patient considering their onset time and etiology, although these findings need to be generalized with a large sample size.

Attention, memory, and auditory processing in 10- to 15-year-old children with listening difficulties.

The aim of this study was to examine attention, memory, and auditory processing in children with reported listening difficulty in noise (LDN) despite having clinically normal hearing. Twenty-one children with LDN and 15 children with no listening concerns (controls) participated. The clinically normed auditory processing tests included the Frequency/Pitch Pattern Test (FPT; Musiek, 2002), the Dichotic Digits Test (Musiek, 1983), the Listening in Spatialized Noise-Sentences (LiSN-S) test (Dillon, Cameron, Glyde, Wilson, & Tomlin, 2012), gap detection in noise (Baker, Jayewardene, Sayle, & Saeed, 2008), and masking level difference (MLD; Wilson, Moncrieff, Townsend, & Pillion, 2003). Also included were research-based psychoacoustic tasks, such as auditory stream segregation, localization, sinusoidal amplitude modulation (SAM), and fine structure perception. All were also evaluated on attention and memory test batteries. The LDN group was significantly slower switching their auditory attention and had poorer inhibitory control. Additionally, the group mean results showed significantly poorer performance on FPT, MLD, 4-Hz SAM, and memory tests. Close inspection of the individual data revealed that only 5 participants (out of 21) in the LDN group showed significantly poor performance on FPT compared with clinical norms. Further testing revealed the frequency discrimination of these 5 children to be significantly impaired. Thus, the LDN group showed deficits in attention switching and inhibitory control, whereas only a subset of these participants demonstrated an additional frequency resolution deficit.

Effects of Meditation on Temporal Processing and Speech Perceptual Skills in Younger and Older Adults

The purpose of this study was to assess the temporal processing and speech perception abilities in older adults who were practicing meditation for more than five years. Participants were comprised of three groups, 30 young adults (“YA”) in the age range of 20–30 years, 30 older adults in the age range of 50–65 years who practiced meditation for a period of five years or more (effective meditators “EM”), and 51 age matched older adults who did not have any experience of meditation (non-meditators “NM”). Temporal processing was evaluated using gap detection in noise, duration discrimination, modulation detection, and backward masking and duration pattern tests. Speech perception was measured in presence of a four-talker babble at −5 dB signal to noise ratio and with the vocoded stimuli. Results revealed that EM group performed significantly better than NM group in all psychophysical and speech perception tasks except in gap detection task. In the gap detection task, two groups did not differ significantly. Furthermore, EM group showed significantly better modulation detection thresholds compared to YA. Results of the study demonstrate that the practice of meditation not only offsets the decline in temporal and speech processing abilities due to aging process but also improves the ability to perceive the modulations compared to young adults.

Psychometric functions for gap detection in noise measured from young and aged subjects.

Psychometric functions for gap detection of temporal gaps in wideband noise were measured in a "yes/no" paradigm from normal-hearing young and aged subjects with closely matched audiograms. The effects of noise-burst duration, gap location, and uncertainty of gap location were tested. A typical psychometric function obtained in this study featured a steep slope, which was independent of most experimental conditions as well as age. However, gap thresholds were generally improved with increasing duration of the noise burst for both young and aged subjects. Gap location and uncertainty had no significant effects on the thresholds for the young subjects. For the aged subjects, whenever the gap was sufficiently away from the onset or offset of the noise burst, detectability was robust despite uncertainty about the gap location. Significant differences between young and aged subjects could be observed only when the gap was very close to the signal onset and offset.

The effects of sinusoidal amplitude modulation on gap detection in noise

The purpose of this study was to investigate the effects of envelope fluctuation on temporal gap detection. Temporal gap detection thresholds were measured in wideband noisebursts that had been amplitude modulated by a very low-frequency sinusoid. Detection was studied at six modulation depths and in four phase conditions which placed the onset of the silent gap at different amplitudes on the temporal envelope of the waveform. Gap thresholds were obtained in a 3IFC paradigm in four young, normal-hearing subjects. The smallest mean gap threshold, 3.5 ms, was obtained for unmodulated noisebursts. The largest mean gap threshold, 25.7 ms, was obtained at a modulation depth of 100%. Phase did not significantly affect gap detection until modulation depth was increased to 40%. At deeper depths of modulation, gap thresholds were smallest, but also most variable, when the gap onset was placed at a peak in the waveform envelope and largest when the gaps were centered on an envelope minimum or randomly placed. Results of this study are consistent with previous findings and the hypothesis that gap detection is dependent on the similarity of the gap itself to inherent fluctuations in the stimulus envelope, reflecting coherence in terms of phase and depth of envelope fluctuation.

The effects of signal frequency and absolute bandwidth on gap detection in noise.

Whether temporal resolution in noisebursts is primarily determined by the highest frequency component in the signal or its absolute bandwidth remains unclear. In this study, the absolute bandwidths and upper cutoff frequencies of signal noisebursts were varied across broad frequency ranges, several times greater than previously jointly studied. The purpose was to determine how each independently affects detection, taking into consideration that bandwidth effects at one signal frequency might be very different from bandwidth effects at another. Gap detection thresholds were obtained for five subjects with normal hearing in a 2 IFC paradigm. Signals were noisebursts whose bandwidths and upper cutoff frequencies varied among 1, 2, 4, 8, and 12 kHz. Their duration was 150 ms and they were presented at an overall level of 75 dB SPL above a 45 dB SPL white noise floor. The largest mean gap detection threshold, 6.98 ms, was obtained for a noiseburst with a bandwidth of 1 kHz and upper cutoff frequency of 12 kHz. The smallest mean gap detection threshold, 2.22 ms, was found with a bandwidth and upper cutoff frequency of 12 kHz. Significant interactions were found to exist between absolute bandwidth and upper cutoff frequency. Although gap detection thresholds generally decreased with increasing signal frequency and bandwidth, the pattern was complex. When the absolute bandwidth was at least one-half the upper cutoff frequency then upper cutoff frequency and not bandwidth determined gap sensitivity; but when the absolute bandwidth was less than one-half of the upper frequency, then both determined gap thresholds.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of gaps in noise by budgerigars ( Melopsittacus undulatus) and zebra finches ( Poephila guttata)

Temporal gap detection thresholds were obtained for two species of birds, budgerigars and zebra finches, which are known to have different auditory filter bandwidths. Both species showed gap detection thresholds of about 2.5 msec for broadband noise stimuli. Comparing octave bands of noise centered at 1, 3 and 5 kHz, zebra finches showed the smallest gap thresholds for the noise band centered at 5 kHz whereas budgerigars showed the smallest gap detection thresholds for the noise band centered at 3 kHz. The results from zebra finches are generally consistent with filter theories of auditory spectro-temporal perception whereas the result from budgerigars are not. In aggregate, these comparative data suggest the relation between spectral and temporal resolving power in these two species may involve different mechanisms.

Temporal aspects of the auditory system: Gap detection and the modulation transfer function

A three-stage model consisting of a bandpass filter followed by a nonlinear element and a low-pass filter is often used to model temporal processing in the auditory system [e.g., N. F. Viemeister, J. Acoust. Soc. Am. 66, 1364–1380 (1979)]. Two experimental paradigms, the detection of gaps in noise and of sinusoidal modulation of noise, have been used to estimate the parameters of this model. A simulation of this model was used to “listen” to waveforms in gap detection and modulation detection experiments. Responses of the simulator were based on statistical calculations at the output of the low-pass filter stage of the model. Our decision statistic was the maximum-to-minimum ratio of the waveform from the low-pass filter. Good agreement between the data produced by normal-hearing human observers and the simulator occurred when the bandwidth of the initial filter was 4000 Hz and the time constant of the low-pass stage was 3 ms. [Research supported by NSF.]

Temporal gap detection in noise as a function of frequency, bandwidth, and level.

Temporal gap resolution is measured with Békésy tracking procedure and filtered noise stimuli in the frequency range below 6000 Hz. Stimulus parameters include high-pass and low-pass cutoff frequency, band center frequency, bandwidth in a 2-oct range, and signal level in the low-to-moderate intensity range. The pattern of results indicates that gap resolution improves with an increase in stimulus frequency in a manner that can be described by a linear function with a slope of about 2 ms/oct. This relationship applies to signal levels greater than 25--30 dB SL. A linear trend also describes gap threshold as a function of the empirical critical bandwidth within the same frequency range. Implications of the results for simple functional models of temporal processing are examined.

Perception of auditory temporality in several species of birds

Thresholds for the detection of gaps in noise, temporal integration, and difference limens for duration were measured in several species of birds using avoidance conditioning and the method of limits procedures previously described for the parakeet. The threshold for the detection of gaps in white noise bursts is about 3–5 msec for the house finch. Temporal integration functions showing absolute threshold as a function of tone duration for field sparrows and parakeets reveal a “time constant” of 200–300 msec. Difference limens for duration obtained at six durations of a 2.86-kHz tone for the parakeet show Weber fractions, ΔD/D, in the range of 0.10–0.20. These data are compared to similar data available for the human and the results of these experiments are discussed in relation to the characteristics of avain vocalizations and the role of hearing in song learning and song production. [Work supported by NSF grant BNS75-19431.]