Non-simultaneous Masking of Speech in Noise: Normal-hearing Children and Adults
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Subjects suffering from noise-induced hearing loss (NIHL) with or without hearing loss at 2 kHz were examined by speech audiometry with a three-digit test, bisyllabic and monosyllabic PB word lists in silence, and in USASI noise with a masking effect of 44 dB and 68 dB at 1 kHz. Subjects with up to 20 dB hearing loss at 2 kHz had almost the same speech comprehension in noise as normal hearing subjects. Subjects with hearing loss greater than 20 dB at 2 kHz had increasing discrimination loss at increasing noise levels. They also needed a signal-to-noise ratio better than normal-hearing persons would yield at the noise levels used. The evaluation of hearing disablement in occupational noise-included hearing loss should therefore be based for one-half on the results of speech audiometry in silence, and for the other half, in noise.
Noise-induced hearing loss
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The effect of amplitude-modulated (AM) noise on speech recognition in listeners with normal and impaired hearing was investigated in two experiments. In the first experiment nonsense syllables were presented in high-pass steady-state or AM noise to determine whether the release from masking in AM noise relative to steady-state noise was significantly different between normal-hearing and hearing-impaired subjects when the two groups listened under equivalent masker conditions. The normal-hearing subjects were tested in the experimental noise under two conditions: (a) in a spectrally shaped broadband noise that produced pure tone thresholds equivalent to those of the hearing-impaired subjects, and (b) without the spectrally shaped broadband noise. The release from masking in AM noise was significantly greater for the normal-hearing group than for either the hearing-impaired or masked normal-hearing groups. In the second experiment, normal-hearing and hearing-impaired subjects identified nonsense syllables in isolation and target words in sentences in steady-state or AM noise adjusted to approximate the spectral shape and gain of a hearing aid prescription. The release from masking was significantly less for the subjects with impaired hearing. These data suggest that hearing-impaired listeners obtain less release from masking in AM noise than do normal-hearing listeners even when both the speech and noise are presented at levels that are above threshold over much of the speech frequency range.
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threshold" complaints are voiced by an additional 26 million people who have hearing thresholds within normal limits (WNL), when tested with a standard audiologic test battery in quiet.People who consult physicians and audiologists complaining of HD or SIN problems in the presence of thresholds WNL often present a dilemma for hearing professionals.Specifically, they have normal hearing on standard tests, but still complain of SIN and HD problems.Of course, the given scenario begs the question, "What is the appropriate resolution for these problems?"Persons with supra-threshold complaints and normal thresholds are often counseled about taking advantage of "happy talk" strategies.That is, they are generally told something along the lines of "The good news is you have normal hearing…" and they are instructed to use better lighting, and perhaps to focus on visual cues and/or visual redundancy, and to reduce the distance between the talker and the listener and more.However, although these strategies may offer some benefit, they may also frustrate patients further and may not be accepted as being particularly helpful or realistic solutions to their problems.Of note, when adults report they only have difficulty in challenging acoustic situations or difficulty understanding SIN, they are usually reporting accurate and sophisticated observations.Further, because they are adults, it is likely they have already tried many of these same apparent and obvious solutions without substantial success and have only come to see hearing care professionals after having exhausted these same solutions.Unfortunately, many supra-threshold complaints are overlooked, or are not treated seriously, and may be explained as due to "normal aging" or ignored.Thus, many of these individuals "slip through the cracks" or fail to receive early intervention for their HDs and/or SIN problems.Delays in diagnosis and treatment often perpetuate these patients' problems and can affect the overall quality of life (QoL) for them and their families.Physicians and audiologists can and should do more for people with supra-threshold auditory complaints. Best practicesMany physicians and audiologists practice with an eye toward detecting otologic diseases which may require medical or surgical interventions, and as anticipated, the vast majority of these same problems (i.e., those in need of medical or surgical attention) are identified by the standard audiologic battery (i.e., air-and boneconduction pure tones and speech audiometry in quiet).Unfortunately, this same battery often fails to detect listening difficulties and may not accurately reflect how patients function in their daily lives.Therefore, many patients are likely not identified or informed about available tools designed to improve signal-to-noise ratios (SNRs) which could alleviate or reduce their HD or SIN problems.Indeed, hearing loss is not the primary concern for people with normal thresholds who complain of hearing difficulty or SIN problems, the primary issue is measuring, documenting and improving the signal-to-noise ratio (SNR) required to understand SIN.Importantly, improving the SNR is "always helpful to a listener." 1 Had these same individuals been tested and managed according to the American Academy of Audiology (AAA) or the American Speech Language Hearing Association (ASHA) Best Practice (BP) guidelines, 2 it is likely their HD and/or SIN problems would be discovered, documented, and scheduled for appropriate treatments in a timely manner.
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Pure-tone threshold audiometry is currently the standard test of hearing. However, in everyday life, we are more concerned with listening to speech of moderate loudness and, specifically, listening to a particular talker against a background of other talkers. FreeHear delivers strings of three spoken digits (0–9, not 7) against a background babble via three loudspeakers placed in front and to either side of a listener. FreeHear is designed as a rapid, quantitative initial assessment of hearing using an adaptive algorithm. It is designed especially for children and for testing listeners who are using hearing devices. In this first report on FreeHear, we present developmental considerations and protocols and results of testing 100 children (4–13 years old) and 23 adults (18–30 years old). Two of the six 4 year olds and 91% of all older children completed full testing. Speech reception threshold (SRT) for digits and noise colocated at 0° or separated by 90° both improved linearly across 4 to 12 years old by 6 to 7 dB, with a further 2 dB improvement for the adults. These data suggested full maturation at approximately 15 years old SRTs at 90° digits/noise separation were better by approximately 6 dB than SRTs colocated at 0°. This spatial release from masking did not change significantly across age. Test–retest reliability was similar for children and adults (standard deviation of 2.05–2.91 dB SRT), with a mean practice improvement of 0.04–0.98 dB. FreeHear shows promise as a clinical test for both children and adults. Further trials in people with hearing impairment are ongoing.
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This study evaluated the influence of hearing loss on children's speech-perception abilities in a speech-shaped noise or a two-talker masker. For both masker conditions, it was predicted that children with hearing loss would require a more advantageous signal to noise ratio (SNR) than children with normal hearing to achieve the same criterion level of performance. However, it was hypothesized that the performance gap between children with hearing loss and children with normal hearing would be larger in the two-talker than in the speech-shaped noise masker.A repeated-measures design compared the spondee identification performance of two age groups of children with hearing loss (9-11 and 13-17 years of age) and a group of children with normal hearing (9-11 years of age) in continuous speech-shaped noise or a two-talker masker. Estimates of the SNR required for 70.7% correct spondee identification were obtained using an adaptive, four-alternative, forced-choice procedure. Children were tested in the sound field. Children with hearing loss wore their personal hearing aids at their regular settings during testing.Both groups of children with hearing loss performed more poorly than children with normal hearing in the speech-shaped noise masker. Younger children required an additional 2.7 dB SNR and older children required an additional 4.7 dB SNR to achieve the same level of performance as children with normal hearing. This disadvantage decreased to 8.1 dB for both age groups of children with hearing loss in the two-talker masker. For children with hearing loss, degree of hearing loss was significantly correlated with performance in the speech-shaped noise masker, but not in the two-talker masker.A larger performance gap was observed between children with hearing loss and children with normal hearing in competing speech than in steady state noise. These results are consistent with the hypothesis that hearing loss influenced children's perceptual processing abilities.
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Psychoacoustics
Auditory masking
Intelligibility (philosophy)
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We studied the effect of speech time compression (TC), alone and in the presence of competing babble, in 24 adults and 24 children. Both adults and children showed significant decreases in speech recognition when speech was compressed at a rate of 60 percent, as compared with recognition of normal-rate speech. Listening to time-compressed speech in a binaural homophasic mode resulted in better speech recognition than in a monaural mode for both adults and children. When speech was antiphasic, both adults and children demonstrated a release from masking for normal-rate (0% compression) and 60 percent time-compressed speech. When both groups listened to speech that had been compressed and presented in a babble, their performance supported a multiplicative distortion theory. The results support the importance of binaural hearing for optimizing auditory performance in difficult listening situations.
Monaural
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Despite considerable effort, monaural (single-microphone) algorithms capable of increasing the intelligibility of speech in noise have remained elusive. Successful development of such an algorithm is especially important for hearing-impaired (HI) listeners, given their particular difficulty in noisy backgrounds. In the current study, an algorithm based on binary masking was developed to separate speech from noise. Unlike the ideal binary mask, which requires prior knowledge of the premixed signals, the masks used to segregate speech from noise in the current study were estimated by training the algorithm on speech not used during testing. Sentences were mixed with speech-shaped noise and with babble at various signal-to-noise ratios (SNRs). Testing using normal-hearing and HI listeners indicated that intelligibility increased following processing in all conditions. These increases were larger for HI listeners, for the modulated background, and for the least-favorable SNRs. They were also often substantial, allowing several HI listeners to improve intelligibility from scores near zero to values above 70%.
Intelligibility (philosophy)
Monaural
Hearing impaired
Hearing aid
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The author investigated the masking of hearing for spoken voice by which noise in the persons with deafness, and the following subjects were studied:(1) Relation between the white noise level and speech reception threshold shift.(2) Studies on the effects of white noise on discrimination ability.(3) The meaning of speech noise audiometry differential diagnosis of different kinds ofdeafness.
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Objective: This study examined speech recognition in noise for children with hearing loss, compared it to recognition for children with normal hearing, and examined mechanisms that might explain variance in children's abilities to recognize speech in noise. Design: Word recognition was measured in two levels of noise, both when the speech and noise were co-located in front and when the noise came separately from one side. Four mechanisms were examined as factors possibly explaining variance: vocabulary knowledge, sensitivity to phonological structure, binaural summation, and head shadow. Study sample: Participants were 113 eight-year-old children. Forty-eight had normal hearing (NH) and 65 had hearing loss: 18 with hearing aids (HAs), 19 with one cochlear implant (CI), and 28 with two CIs. Results: Phonological sensitivity explained a significant amount of between-groups variance in speech-in-noise recognition. Little evidence of binaural summation was found. Head shadow was similar in magnitude for children with NH and with CIs, regardless of whether they wore one or two CIs. Children with HAs showed reduced head shadow effects. Conclusion: These outcomes suggest that in order to improve speech-in-noise recognition for children with hearing loss, intervention needs to be comprehensive, focusing on both language abilities and auditory mechanisms.
Unilateral hearing loss
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