The effect of speech presentation level on acceptance of background noise in listeners with normal hearing

A method has been established to measure the maximum acceptable background noise level (BNL) for a listener, while listening to speech at the most comfortable listening level (MCL). The acceptable noise level (ANL) is the difference between BNL and MCL. In the present study, the ANL procedure was used to measure acceptance of noise, first, in the presence of speech at MCL and, then, for speech presented at much lower and higher levels in listeners with normal hearing. This study used the term ANL to describe the results obtained at MCL and also at other speech presentation levels. The mean ANL at MCL was 15.5 dB, which is comparable to results obtained by previous investigators. ANL increases systematically with speech presentation level. Mean ANLs ranged from 10.6 dB when speech was presented at 20 dB HL to 24.6 dB when speech was presented at 76 dB HL. The results indicated that the acceptance of noise depends significantly on speech presentation level.     

Effects of speech signal content and speaker gender on acceptance of noise in listeners with normal hearing

Abstract

Objective: The purpose of this research was to determine if the content and/or speaker gender of a running speech sample affected the acceptance of background noise within a participant. Design: A male and a female recording of the Arizona Travelogue (Cosmos Inc.) and the ipsilateral competing message (ICM) from the synthetic sentence identification with ICM were created and used as the experimental speech signals. Two acceptable noise level measurements were obtained and averaged for each condition. Twenty-one participants rated interest level in the speech sample for each condition. Study Sample: Forty-three listeners with normal hearing participated. Results: Interest level was significantly greater for the ICM than the Arizona Travelogue speech samples, and was significantly greater for female samples. Neither the content of the sample nor the gender of the speaker significantly affected the most comfortable level or the acceptable noise level. Conclusions: Findings suggest that the acceptable noise level can be measured using various types of speech signals for normal-hearing listeners.

Sumario

Objetivo: El propósito de esta investigación fue determinar si el contenido y/o el género del locutor en una muestra de lenguaje corrido afectaba la aceptación del ruido de fondo en un mismo participante. Diseño: Se realizóuna grabación con la participación de un hombre y una mujer del Arizona Travelogue (Cosmos Inc.) y del Mensaje Competitivo Ipsilateral (ICM) de la prueba de identificación de Frases Sintéticas con ICM, y se creó una material que fue utilizado como señal lingûstica experimental. Se obtuvieron dos mediciones de niveles de ruido aceptables y se promediaron para cada condición. Veintiún participantes calificaron el nivel de interés de la muestra de lenguaje para cada condición. Muestra del Estudio: Participaron cuarenta y tres sujetos con audición normal. Resultados: El nivel de interés fue significativamente mayor para las muestras de lenguaje del ICM que para las del Arizona Travelogue y estas fueron significativamente mayores para muestras grabadas por mujeres. Ni el contenido de la muestra ni el género del locutor afectó significativamente el nivel más confortable o el nivel aceptable de ruido. Conclusiones: Los hallazgos sugieren que el nivel aceptable de ruido puede medirse usando varios tipos de señales de lenguaje para oyentes con audición normal.     

Contribution of high-frequency information to the acceptance of background noise in listeners with normal and impaired hearing

PURPOSE: To determine whether information beyond 2.0 kHz affected the acceptance of background noise in listeners with normal and/or impaired hearing. METHOD: Speech stimuli (Arizona Travelogue) and multitalker babble were low-pass filtered at cutoff frequencies of 2.0, 4.0, and 6.0 kHz and presented using an adaptive paradigm to determine the most comfortable level (MCL) and acceptable noise level (ANL) for 4 experimental conditions (unfiltered, 2.0, 4.0, and 6.0 kHz) for each listener. RESULTS: MCL for listening to speech in quiet was significantly increased when the speech stimuli were low-pass filtered at 2.0 kHz relative to the unfiltered and 6.0-kHz conditions. Acceptance of background noise was significantly poorer when the speech and noise stimuli were low-pass filtered at 2.0 kHz relative to the 6.0-kHz condition. Listeners with impaired hearing sensitivity had significantly greater MCL values than listeners with normal hearing, but ANL values were not significantly affected by the hearing sensitivity of the listener. CONCLUSIONS: Information beyond 2.0 kHz significantly affected MCL and ANL values in both listeners with normal hearing and impaired hearing; however, effects for both the MCL and ANL measurements were small and may not be significant clinically.     

Intelligibility of modified speech for young listeners with normal and impaired hearing.

Exposure to modified speech has been shown to benefit children with language-learning impairments with respect to their language skills (M. M. Merzenich et al., 1998; P. Tallal et al., 1996). In the study by Tallal and colleagues, the speech modification consisted of both slowing down and amplifying fast, transitional elements of speech. In this study, we examined whether the benefits of modified speech could be extended to provide intelligibility improvements for children with severe-to-profound hearing impairment who wear sensory aids. In addition, the separate effects on intelligibility of slowing down and amplifying speech were evaluated. Two groups of listeners were employed: 8 severe-to-profoundly hearing-impaired children and 5 children with normal hearing. Four speech-processing conditions were tested: (1) natural, unprocessed speech; (2) envelope-amplified speech; (3) slowed speech; and (4) both slowed and envelope-amplified speech. For each condition, three types of speech materials were used: words in sentences, isolated words, and syllable contrasts. To degrade the performance of the normal-hearing children, all testing was completed with a noise background. Results from the hearing-impaired children showed that all varieties of modified speech yielded either equivalent or poorer intelligibility than unprocessed speech. For words in sentences and isolated words, the slowing-down of speech had no effect on intelligibility scores whereas envelope amplification, both alone and combined with slowing-down, yielded significantly lower scores. Intelligibility results from normal-hearing children listening in noise were somewhat similar to those from hearing-impaired children. For isolated words, the slowing-down of speech had no effect on intelligibility whereas envelope amplification degraded intelligibility. For both subject groups, speech processing had no statistically significant effect on syllable discrimination. In summary, without extensive exposure to the speech processing conditions, children with impaired hearing and children with normal hearing listening in noise received no intelligibility advantage from either slowed speech or envelope-amplified speech.     

Across-frequency comparison of temporal speech information by listeners with normal and impaired hearing.

Listeners with normal hearing (NH) and with sensorineural hearing impairment (HI) were tested on a speech-recognition task requiring across-frequency integration of temporal speech information. Listeners with NH correctly identified a majority of key words in everyday sentences when presented with a synchronous pair of speech-modulated tones at 750 and 3,000 Hz. They could tolerate small amounts (12.5 ms) of across-frequency asynchrony, but performance fell as the delay between bands was increased to 100 ms. Listeners with HI performed more poorly than those with NH when presented with synchronous across-frequency information. Further, performance of listeners with HI fell as a function of asynchrony more steeply than that of their NH counterparts. These results suggest that listeners with HI have particular difficulty comparing and effectively processing temporal speech information at different frequencies. The increased influence of asynchrony indicates that these listeners are especially hindered by slight disruptions in across-frequency information, which implies a less robust comparison mechanism. The results could not be attributed to differences in signal or sensation level, or in listener age, but instead appear to be related to the degree of hearing loss. This across-frequency deficit is unlikely to be attributed to known processing difficulties and may exist in addition to other known disruptions.     

Effects of noise and reverberation on the precedence effect in listeners with normal hearing and impaired hearing

The purpose of this study was to determine the effects of reverberation and noise on the precedence effect in listeners with hearing loss. Lag burst thresholds (LBTs) for 4-ms noise bursts were obtained for 2 groups of participants: impaired hearing and normal hearing. Data were collected in reverberant and anechoic environments in quiet and noise, at sensation levels of 10, 20, 30, 40, and 50 dB. Results indicated a significant effect of reverberation on LBTs for both participant groups. LBTs increased with sensation level in the reverberant environment and decreased with increasing sensation level in the anechoic environment. There was no effect of hearing loss on LBTs. When the change in LBT due to noise was compared, the effect of noise depended on group and environment, with a greater effect of noise on the performance of listeners with impaired hearing. It is likely that the ability to fuse direct sounds and early reflections is degraded in listeners with impaired hearing and that this contributes to the difficulties experienced by these listeners in reverberation and noise.     

Modulation detection interference in listeners with normal and impaired hearing.

Listeners were asked to detect amplitude modulation (AM) of a target (or signal) carrier that was presented in isolation or in the presence of an additional (masker) carrier. The signal was modulated at a rate of 10 Hz, and the masker was unmodulated or was modulated at a rate of 2, 10, or 40 Hz. Nine listeners had normal hearing, 4 had a bilateral hearing loss, and 4 had a unilateral hearing loss; those with a unilateral loss were tested in both ears. The listeners with a hearing loss had normal hearing at 1 kHz and a 30- to 40-dB loss at 4 kHz. The carrier frequencies were 984 and 3952 Hz. In one set of conditions, the lower frequency carrier was the signal and the higher frequency carrier was the masker. In the other set, the reverse was true. For the impaired ears, the carriers were presented at 70 dB SPL. For the normal ears, either the carriers were both presented at 70 dB SPL or the higher frequency carrier was reduced to 40 dB SPL to simulate the lower sensation level experienced by the impaired ears. There was considerable individual variability in the results, and there was no clear effect of hearing loss. These results suggest that a mild, presumably cochlear hearing loss does not affect the ability to process AM in one frequency region in the presence of competing AM from another region.     

Binaural gap duration discrimination in listeners with impaired hearing and normal hearing

OBJECTIVE: This study was designed to measure the ability of listeners with and without sensorineural hearing loss to discriminate silent gaps between noise band markers of different frequencies presented in an anechoic and a reverberant listening environment. DESIGN: A two-interval, two-alternative, forced-choice paradigm was used to measure gap discrimination ability for six listeners with normal-hearing and six listeners with sensorineural hearing impairment. Marker stimuli were narrow bands of noise centered at frequencies from 500 to 7000 Hz. The center frequency of the leading marker was held constant at 2000 Hz and the center frequency of the trailing marker was varied randomly across runs. Stimuli were presented in two virtual listening environments (anechoic and reverberant). The listeners' task was to indicate which interval contained the marker pair separated by the larger silent gap. Gap discrimination was measured as a function of the center frequency of the trailing marker and as a function of listening environment. RESULTS: Gap discrimination thresholds (msec) varied as a function of the center frequency of the trailing marker. As the trailing marker frequency increased above and decreased below the leading marker frequency (2000 Hz), gap thresholds increased significantly. Hearing loss and listening environment did not have a significant effect on gap discrimination thresholds. Analysis of the gap discrimination functions revealed significantly steeper slopes for trailing marker frequencies below 2000 Hz than for trailing marker frequencies above 2000 Hz. A possible age effect was observed in the data and significant correlations were found between age and function slopes for several conditions. CONCLUSIONS: Gap discrimination becomes more difficult as the frequency disparity between leading and trailing noise bands increases. This pattern of results occurs independent of hearing loss but may be influenced by listener age.     

Learning effect observed for the speech reception threshold in interrupted noise with normal hearing listeners

Traditionally, the speech reception threshold (SRT) for sentences in noise is measured in stationary speech-shaped noise; however, non-stationary masking noises are gradually becoming more common. A previous study by Rhebergen et al. () suggested that a learning effect might be present for the SRT in interrupted noise but not in stationary noise. The current study tested if a stable SRT for female or male speech is reached by determining SRTs in listeners with normal hearing in either stationary or 8-Hz interrupted noise after five replications. Contrary to repeated SRT measurements in stationary noise, a significant improvement was observed for SRTs in interrupted noise with replication. For both speech materials, after five replications, the SRT in interrupted noise improved about 3 to 4 dB in comparison to the first SRT. Stable thresholds seem to be reached after about two replications. This experiment shows that there is a substantial learning effect present in SRT measurements with interrupted noise but not in stationary noise. With non-stationary noise, it is recommended to include a repeated measures design.     

Learning effect observed for the speech reception threshold in interrupted noise with normal hearing listeners

Traditionally, the speech reception threshold (SRT) for sentences in noise is measured in stationary speech-shaped noise; however, non-stationary masking noises are gradually becoming more common. A previous study by Rhebergen et al. (2006) suggested that a learning effect might be present for the SRT in interrupted noise but not in stationary noise. The current study tested if a stable SRT for female or male speech is reached by determining SRTs in listeners with normal hearing in either stationary or 8-Hz interrupted noise after five replications. Contrary to repeated SRT measurements in stationary noise, a significant improvement was observed for SRTs in interrupted noise with replication. For both speech materials, after five replications, the SRT in interrupted noise improved about 3 to 4 dB in comparison to the first SRT. Stable thresholds seem to be reached after about two replications. This experiment shows that there is a substantial learning effect present in SRT measurements with interrupted noise but not in stationary noise. With non-stationary noise, it is recommended to include a repeated measures design.     

Development and evaluation of the Mandarin speech signal content on the acceptable noise level test in listeners with normal hearing in mainland China

Abstract

Objective: To develop and evaluate the Mandarin speech signal content on the acceptable noise level (ANL) test in listeners with normal hearing in mainland China. Design: The Mandarin ANL tests were conducted using three different sets of Mandarin running speech materials which were chosen from textbooks for primary school, secondary school, and high school, respectively. For each discourse, two ANL measurements were obtained and averaged for each experimental condition using ANL test procedures. Study sample: Thirty-one normal-hearing listeners participated in this study. Results: There were significant differences for ANLs among the normal-hearing listeners, but no differences were found for MCLs and ANLs for the three sets of test materials. The Pearson correlations suggested significant correlations between MCL and ANL among the three test materials; also the results showed that the correlation coefficient between MCL-ANL of the primary material was much better than other two materials. Conclusions: (1) The contents of different Mandarin running speeches may not affect the acceptable noise level in Mandarin normal-hearing listeners; (2) The running speech selected from the primary school ought to be used as the Mandarin acceptable noise level test material to evaluate the outcomes of hearing aid fitting.

Sumario

Objetivo: Desarrollar y evaluar el contenido de la señal de lenguaje en mandarín con la Prueba de Nivel de Ruido Aceptable (ANL), en sujetos con audición normal de China continental. Diseño: Las pruebas de ANL en mandarín fueron conducidas usando tres diferentes tipos de contenidos provenientes de materiales de lenguaje en mandarín escogidos de libros de texto para la escuela primaria, secundaria y preparatoria, respectivamente. Para cada discurso, se obtuvieron dos mediciones de ANL y se promediaron para cada condición experimental, usando los procedimientos de la prueba de ANL. Muestra del Estudio: Participaron en el estudio treinta y un sujetos con audición normal. Resultados: Existieron diferencias significativas de ANL entre los sujetos con audición normal, pero no se encontraron diferencias en el MCL y ANL de los tres materiales. Las correlaciones de Pearson sugirieron correlaciones significativas entre el MCL y ANL de los tres materiales; también los resultados mostraron que el coeficiente de correlación entre MCL-ANL del material de primaria fue mucho mejor que con los otros dos materiales. Conclusiones: (1) el contenido de los diferentes discursos en mandarín puede no afectar el nivel aceptable de ruido en oyentes de mandarín con audición normal; (2) el discurso seleccionado de la escuela primaria debería ser utilizado como el material de prueba en mandarín con un nivel aceptable de ruido, para evaluar los resultados de la adaptación de auxiliares auditivos.     

Lexical and talker effects on word recognition among native and non-native listeners with normal and impaired hearing.

Evidence suggests that word recognition depends on numerous talker-, listener-, and stimulus-related characteristics. The current study examined the effects of talker variability and lexical difficulty on spoken-word recognition among four groups of listeners: native listeners with normal hearing or hearing impairment (moderate sensorineural hearing loss) and non-native listeners with normal hearing or hearing impairment. The ability of listeners to accommodate trial-to-trial variations in talkers' voice was assessed by comparing recognition scores for a single-talker condition to those obtained in a multiple-talker condition. Lexical difficulty was assessed by comparing word-recognition performance between lexically "easy" and "hard" words as determined by frequency of occurrence in language and the structural characteristics of similarity neighborhoods formalized in the Neighborhood Activation Model. An up-down adaptive procedure was used to determine the sound pressure level for 50% performance. Non-native listeners in both normal-hearing and hearing-impaired groups required greater intensity for equal intelligibility than the native normal-hearing and hearing-impaired listeners. Results, however, showed significant effects of talker variability and lexical difficulty for the four groups. Structural equation modeling demonstrated that an audibility factor accounts for 2-3 times more variance in performance than does a linguistic-familiarity factor. However, the linguistic-familiarity factor is also essential to the model fit. The results demonstrated effects of talker variability and lexical difficulty on word recognition for both native and nonnative listeners with normal or impaired hearing. The results indicate that linguistic and indexical factors should be considered in the development of speech-recognition tests.     

Speech perception in noise for bilingual listeners with normal hearing

Objective: The purpose of this study was to determine if speech-in-noise ability, as measured by SNR-50 and SNR loss in bilingual Spanish listeners with normal hearing, was affected by test difficulty. Design: Quasi-experimental, non-randomized intervention study. Study sample: Two groups of adult listeners participated: monolingual English listeners with normal hearing (N?=?12) and bilingual Spanish listeners with normal hearing who were proficient in English (N?=?10). The quick speech-in-noise (QuickSIN), the Bamford-Kowal-Bench speech-in-noise (BKB-SIN), and the words-in-noise (WIN) tests were used to assess signal-to-noise ratio (SNR) loss and SNR-50 for both groups. Results: Despite the fact that the bilinguals had normal hearing and were proficient in English, each of the speech-in-noise tests evaluated indicated the Spanish listeners had measurable SNR loss and higher than normal SNR-50s. Performance on the BKB-SIN was best for both groups, indicating test difficulty had a significant impact on speech perception in noise. Conclusions: Bilingual Spanish listeners with normal hearing exhibited a mild SNR loss comparable to that observed for a person with hearing loss. This decreased performance in noise requires an improved SNR for this population to reach a comparable level of comprehension to their monolingual English counterparts.     

The discrimination of mono-syllable words in noise in listeners with normal hearing]

The discrimination of mono-syllable words (67S word-list) pronounced by a male and a female speaker was investigated in noise in 39 normal hearing subjects. The subjects listened to the test words at a constant level of 62 dB together with white or weighted noise in four S/N conditions. By processing the data with logit transformation, S/N-discrimination curves were presumed for each combination of a speech material and a noise. Regardless of the type of noise, the discrimination scores for the female voice started to decrease gradually at a S/N ratio of +10 dB, and reached 10 to 20% at-10 dB. For the male voice in white noise, the discrimination curve was similar to those for the female voice. On the contrary, the discrimination score for the male voice in weighted noise declined rapidly from a S/N ratio of +5 dB, and went below 10% at -5 dB. The discrimination curves seem to be shaped by the interrelations between the spectrum of the speech material and that of the noise.     

Interference and enhancement effects on interaural time discrimination and level discrimination in listeners with normal hearing and those with hearing loss

It is known that many listeners with sensorineural hearing loss (SNHL) have difficulty performing binaural tasks. In this study, interference and enhancement effects on interaural time discrimination and level discrimination were investigated in 4 listeners with normal hearing (NH) and 7 listeners with SNHL. Just-noticeable differences were measured using 1/3-octave narrowband noises centered at 0.5 and 4 kHz. Noises were presented in isolation and together at equivalent sound pressure level (EqSPL) and equivalent sensation level (EqSL). Each noise served as target and distractor in the dual-band conditions. Congruent conditions included interaural differences in both noises that varied together, and incongruent conditions included an interaural difference in one noise with the second noise diotic. No significant enhancement effects were observed for either group in either task. Interference effects for the NH group were limited to the interaural level discrimination task in the 0.5-kHz target and 4-kHz distractor condition. Performance of participants with SNHL was similar to that of the NH group for interaural time discrimination with noises at EqSL but not EqSPL. In interaural level discrimination, listeners with SNHL demonstrated interference with a 4-kHz target and 0.5-kHz distractor. Results indicated that the relative levels of low- and high-frequency targets and distractors could affect binaural performance of individuals with SNHL but that in some conditions listeners with SNHL performed similarly to those with normal hearing. Implications of these results for binaural clinical tests and hearing aid fitting strategies are discussed.     

Assessing speech recognition in noise for listeners with a signal processor hearing aid

Hearing aids with signal processors use advanced circuitry to enhance speech recognition in noise. The effectiveness of these processors has not been well established. The purpose of this study was to evaluate performance on a speech recognition in noise task for listeners wearing a Zeta signal processor aid with the processor turned on and with the processor turned off. In addition, comparisons were made to performance while unaided and aided with a conventional hearing aid. A simple adaptive procedure and a psychometric function were the procedures used. Results for normal-hearing subjects indicate performance was usually better without a hearing aid. Performance when aided was similar for the processor on and the conventional aid. Performance in both of these conditions was clearly better than with the signal processor off. Although results for the hearing-impaired subjects varied widely, there was a trend for better performance with the conventional aid and with the signal processor on than for the signal processor off condition.     

The effect of masking by noise on word discrimination scores in listeners with normal hearing and with noise-induced hearing loss

Patients with high-frequency hearing loss often complain at the Workers' Compensation Board that they find it difficult to hear speech in a noisy environment. This study was undertaken to test the validity of their complaints. The experiment had a 2x3x3 factorial design. The factors were subject group (normal hearing versus sensorineural hearing loss), stimulus level (65, 75, and 85 dB SPL), and speech-to-noise ratio (5, 12, and 19 dB). There were 6 subjects in each condition. Each subject was tested for his speech discrimination with three CID W-22 50-word lists, one in each of the three different speech-to-noise ratios. Both speech and pink noise were presented through loudspeakers in a sound field. The results support the patients' complaints. Possible explanations for the results are discussed.