RESUMEN
This study assessed the effects of spatialized sound presentation on a listener's ability to monitor target (T) messages in the presence of competing (C) messages and high-level (110 dB[A]) background noise (BGN). In a simulated military environment, 8 participants wore two-channel, active noise reduction (ANR) equipped helmets and listened to combinations of T and C messages (89 dB[A] at the ear). T messages were presented synchronously with 0, 1, 2, and 3 C messages in four listening modes: (a) BGN + diotic, (b) BGN + dichotic, (c) BGN + spatial audio, and (d) quiet + spatial audio. Best overall performance occurred in the spatialized modes (c and d) and poorest in the diotic mode (a). As expected, speech recognition was better in quiet than in BGN when multiple C messages were present. Findings indicate that message spatialization in acoustic space improves auditory performance during times of heavy message competition, even in high-level noise. The proposed technology has numerous applications, such as multichannel communications in tactical operations centers, monitoring of complex security systems, and air traffic control.
Asunto(s)
Dispositivos de Protección de la Cabeza , Audición/fisiología , Percepción del Habla/fisiología , Adulto , Análisis de Varianza , Femenino , Humanos , Masculino , RuidoRESUMEN
The goal of the present study was to investigate the human factors issues related to acoustic beacons used for auditory navigation. Specific issues addressed were: (1) the effect of various beacon characteristics on human accuracy in turning toward the direction of the acoustic beacon; (2) the difference between real and virtual environments on human accuracy in turning toward the acoustic beacon; and (3) the perceived sound quality of various acoustic beacons. Three experiments were conducted in which acoustic beacons were presented in a background of 80 dBA pink noise. Results of the localization tasks revealed that (a) presentation mode (continuous versus pulsed beacon sound) did not affect the overall localization accuracy or number of front-back confusion errors; and (b) the type of acoustic beacon affected the size of localization error. Results of the sound quality assessment indicated that listeners had definite preferences regarding the type of sound being used as a beacon, with (a) non-speech beacons preferred over speech beacons, (b) a beacon repetition rate of 1.1 rps preferred over either the 0.7 or 2.5 rps rates, and (c) a continuous operation of a beacon preferred over a pulsed operation. Finally, sound quality ratings and localization errors were highly negatively correlated. This finding demonstrates the usefulness and practical values of sound quality judgements for audio display design and evaluation.
Asunto(s)
Acústica , Localización de Sonidos , Análisis y Desempeño de Tareas , HumanosRESUMEN
The purpose of this study was to measure air-conduction (AC) and bone-conduction (BC) hearing thresholds with pure-tone and filtered sound effect stimuli using standard audiometric equipment. A group of 20 young, normal-hearing listeners participated in the study. Pure-tone stimuli were 250, 500, 1000, 2000, and 4000 Hz. Sound effect stimuli were 12 natural sounds that were spectrally limited to an octave bandwidth centered at either 250, 500, 1000, 2000, or 4000 Hz. The AC and BC detection thresholds were measured using a clinical audiometer (Madsen Orbiter 922) with a B-71 bone oscillator and TDH-50 earphones. Results indicated that detection thresholds for the pure-tone and corresponding octave-band sound effect stimuli were within 3 to 4 dB of each other for both AC and BC testing. The findings support the notion that octave-filtered sound effects are a viable alternative to pure-tone stimuli for use in audiology clinics.
Asunto(s)
Audiometría de Tonos Puros/métodos , Percepción Auditiva/fisiología , Umbral Auditivo/fisiología , Conducción Ósea/fisiología , Adolescente , Adulto , Femenino , Humanos , MasculinoRESUMEN
It is important to select appropriate stimuli and test conditions for developing standardized spatial audiometric tests. In three experiments, binaural detection thresholds (BDTs) for a target signal, located at either 0, 45, 90, 135, 180, 225, 270, or 315 degrees azimuth, were measured in the presence of a masker positioned at one of these eight locations. Target signals included spondaic words from the CID W-1 list. The masker was speech spectrum noise (SSN) or multitalker noise (MTN) presented at a constant level (65 dBA). Bekesy tracking was used to measure BDTs in listeners with normal hearing. Results indicate that BDTs are significantly influenced by the (a) angular separation between the target and noise source and (b) choice of spondaic words used as target stimuli. BDTs for various spondaic words differed as much as 13 dB for a given angular separation. BDTs measured in SSN and MTN for otherwise identical test conditions differed less than 3 dB. A single spondaic word appears to be appropriate for spatial audiometric tests of detection. Nonsignificant differences between masked BDTs obtained for SSN and MTN noises indicate that for spatial detection, the masking effects of these noises are comparable. These results indicate that the development of a clinical test of spatial detection should include the use of SSN and a single spondaic word, with detection being measured for a set of four or five signal and noise source configurations.
Asunto(s)
Audiometría/métodos , Ruido/efectos adversos , Percepción del Habla/fisiología , Adolescente , Adulto , Umbral Auditivo , Femenino , Humanos , MasculinoRESUMEN
OBJECTIVE: The study was designed to assess the effects of background noise level on the detection and localization of speech. DESIGN: The phrase "Where is this?" was presented either in quiet or in a diffuse noise field, through loudspeakers arranged in a 360 degrees azimuth array. The noise conditions included 11 signal to noise ratios (SNRs) ranging from -18 dB SNR to +12 dB SNR in 3 dB increments. Seventeen normal-hearing subjects, aged 18 to 29, participated in the study. RESULTS: Results revealed that in all listening conditions the signal was most easily detected when presented through a loudspeaker positioned at 90 degrees or 270 degrees azimuth. Although the actual level for 50% detection varied as a function of loudspeaker location and SNR, 85% and 100% of all presentations of the signal were detected at -9 dB and -6 dB SNR, respectively. Localization accuracy improved as the SNR increased, ranging from 18% accuracy at -18 dB SNR to 89% at +12 dB SNR. Localization accuracy in quiet was 95%. The data are discussed in reference to patterns of responses at each loudspeaker location. CONCLUSIONS: Detection of the target signal deteriorated as background noise level increased and was dependent on the source location of the incoming signal, as expected. Localization accuracy of the target signal was highly dependent on the SNR and spatial location of the signal source. Detection and localization accuracy data were found to be repeatable across test sessions and response patterns were found to be symmetrical on the right and left sides of the horizontal plane.
Asunto(s)
Ruido , Detección de Señal Psicológica/fisiología , Percepción del Habla/fisiología , Adolescente , Adulto , Umbral Auditivo , Ambiente , Femenino , HumanosRESUMEN
Cognitive slowing that accompanies aging may be reflected in temporal aspects of auditory processing. The purpose of this study was to investigate the effects of age, type of test, and rate of speech on temporal auditory processing. Listeners were divided into three groups: young (25- to 35-year-olds), middle aged (45- to 55-year-olds), and older (65- to 75-year-olds). A method of time compression known as Synchronized Overlap Add (SOLA) was used to increase the rate of speech. This method provides a high-quality speech signal and limits the distortions that may confound the temporal effects on time-compressed tests of speech intelligibility. Listeners performed four speech understanding tasks: sentence repetition, sentence intelligibility rating, connected discourse intelligibility rating, and connected discourse comprehension question and answers at three time compression rates (60%, 70%, and 80%). Although the older group performed more poorly on all tests, only the connected discourse intelligibility rating test was sensitive to age differences among all three groups. This difference did not appear to increase with rate increases but was present only at the 70% compression rate. In addition, variability was especially high in the oldest group of participants.
Asunto(s)
Envejecimiento/fisiología , Percepción del Habla/fisiología , Habla/fisiología , Adulto , Distribución por Edad , Anciano , Cognición , Femenino , Humanos , Masculino , Persona de Mediana Edad , Distribución por Sexo , Factores de TiempoRESUMEN
We measured the accuracy with which sounds heard over a binaural, end-fire array could be located when the angular separation of the array's two arms was varied. Each individual arm contained nine cardioid electret microphones, the responses of which were combined to produce a unidirectional, band-limited pattern of sensitivity. We assessed the desirable angular separation of these arms by measuring the accuracy with which listeners could point to the source of a target sound presented against high-level background noise. We employed array separations of 30 degrees, 45 degrees, and 60 degrees, and signal-to-noise ratios of +5, -5, and -15 dB. Pointing accuracy was best for a separation of 60 degrees; this performance was indistinguishable from pointing during unaided listening conditions. In addition, the processing of the array was modeled to depict the information that was available for localization. The model indicates that highly directional binaural arrays can be expected to support accurate localization of sources of sound only near the axis of the array. Wider enhanced listening angles may be possible if the forward coverage of the sensor system is made less directional and more similar to that of human listeners.
Asunto(s)
Ergonomía , Localización de Sonidos , Adulto , Análisis de Varianza , HumanosRESUMEN
The periodic sampling method of time compression is characterized by periodic removal of segments of speech according to predetermined compression rate (CR) and discard interval length (DIL). Fifteen middle-aged (42-54 years old) and 15 older (60-69 years old) adults participated in the study that assessed the combined effects of CR and DIL on the comprehension of time-compressed speech by aging adults. Three CRs (30, 45, and 60%), seven DILs (35 through 155 msec), and two types of speech materials were used. The subject's task was to report associations among the items mentioned in a time-compressed passage. In all cases, performance of the subjects deteriorated with increasing CR and DIL. The older adults were affected more by CR and DIL values than middle-aged adults. The difference in sentence complexity between the two speech materials affected both groups equally. In general, the results of the study indicated that (a) time-compressed speech differentiates between speech comprehension by middle-aged and older adults and (b) the effects of CR and DIL became more independent with increasing age of the listener and increasing complexity of the speech material. Reported results support the concept that time-compressed speech may be an effective signal in clinical assessment of adults whose auditory complaints are not explained by their peripheral hearing losses.
Asunto(s)
Envejecimiento , Semántica , Percepción del Habla , Adulto , Factores de Edad , Anciano , Audiometría , Femenino , Estado de Salud , Trastornos de la Audición/diagnóstico , Humanos , Masculino , Persona de Mediana EdadRESUMEN
The goal of this study was to determine whether selected sound effects that are spectrally limited to an octave band width could be used as alternative stimuli to pure tones when testing children and other special populations. The uniqueness of octave-band sound effects is that they retain the natural character of everyday sounds while providing frequency-specific information about hearing sensitivity. In this study, 20 normal-hearing adults were asked to detect and recognize octave-band filtered musical and environmental sounds presented in quiet and in multitalker noise. Detection and recognition thresholds for the filtered sound effects were compared with respective pure-tone thresholds obtained at 250, 500, 1000, 2000, and 4000 Hz for the same subjects. Results indicate that filtered sound effects are a promising alternative to pure-tone stimuli for use in audiometric tests. Applications and limitations of filtered sound effects as test stimuli for testing children and adults are discussed.
Asunto(s)
Percepción Auditiva , Adolescente , Adulto , Umbral Auditivo , Femenino , Humanos , MasculinoRESUMEN
Fifteen subjects, aged 60 to 74 years, participated in a study to assess the role of discard interval (DI) length in the understanding of time-compressed connected speech by older adults. The subjects' task was to report associations among the items mentioned in a passage. Results indicate that performance deteriorated gradually until a critical DI of 75 msec was reached, beyond which performance dropped sharply. Results should help in the better understanding of speech perception by older listeners and may be useful in development of a standardized test for evaluating speech understanding in older individuals whose auditory complaints are often not explained by their peripheral hearing loss.
Asunto(s)
Percepción del Habla , Factores de Edad , Anciano , Audiometría de Tonos Puros , Femenino , Trastornos de la Audición/diagnóstico , Humanos , Masculino , Persona de Mediana Edad , Factores de TiempoRESUMEN
The feasibility of using most comfortable loudness (MCL) as a real-world measure of speech attenuation introduced by hearing protection devices (HPDs) was studied. The authors compared three insert HPDs and an earmuff under three test conditions: (a) monaural earphone listening, (b) binaural earphone listening, and (c) sound field listening. The earmuff was used only in the sound-field condition. In addition, three sets of fitting instructions were utilized. Twelve normal hearing subjects participated. Results indicate that MCL shift can be used as a simple measure of speech attenuation provided by HPDs. The observed MCL shifts were affected by the fitting instruction but not by the listening condition. Findings support the notion that MCL-based tests of speech attenuation by HPDs can be conducted reliably both in sound field and under earphones and may be a simple and valid tool for assessing changes in speech audibility due to the wearing of HPDs.
Asunto(s)
Audiometría del Habla , Dispositivos de Protección de los Oídos , Acústica del Lenguaje , Adulto , Femenino , Humanos , MasculinoRESUMEN
Noise attenuation by linear hearing protection devices (HPDs) is considered to be independent of the environmental noise level. Linearity of HPDs is one of the basic assumptions underlying the Real Ear Attenuation at the Threshold (REAT) method of HPD testing, which utilizes quiet conditions. However, non-linear growth of masking at high intensity levels may result in the effects of HPDs on detection of speech and warning signals being different from those at high noise levels. The purpose of this study was to determine if the non-linear growth of masking can affect detection of warble signals by persons using HPDs in wideband noise presented at the 100 dB(A) level. Audiometric thresholds of hearing of 10 listeners were measured under four experimental conditions: (1) noise off, HPDs off (condition C1); (2) noise off, HPDs on (condition C2); (3) noise on, HPDs on (condition C3); and (4) noise on, HPDs off (condition C4). The results of this study indicate that detection of signals by persons using HPDs in noise < 100 dB(A) can be well predicted from noise attenuation characteristics of HPDs measured in quiet without the need for a correction factor accommodating non-linear growth of masking. This finding has implications for predicting the audibility of warning signals in noise by persons wearing HPDs.
Asunto(s)
Audiometría de Tonos Puros , Dispositivos de Protección de los Oídos , Adulto , Humanos , Ruido , Enmascaramiento Perceptual , Valores de ReferenciaRESUMEN
This study determined the acoustical properties of speech known as Lombard Speech produced in background noise. Tape recordings were made for ten normally hearing adults (5 women, 5 men) reading connected speech (131 word passage "My Grandfather") at their most comfortable level in quiet and in wideband, traffic, and multitalker noise delivered through earphones at 70 and 90 dB SPL. Spectral analysis of the recordings revealed that, compared with speech in quiet, Lombard speech was characterized by: (1) an increase in overall SPL; (2) smaller vocal pitch shifts for female than male subjects; (3) shifts in spectral distributions of speech energy; and (4) the same spectral slope above 630 Hz regardless of subject gender, noise level, or noise type. Overall, the results of this study do not provide support for the theory that acoustical properties of Lombard speech are identical with loud speech produced in quiet.
Asunto(s)
Audición/fisiología , Ruido , Acústica del Lenguaje , Estimulación Acústica , Acústica/instrumentación , Adolescente , Adulto , Análisis de Varianza , Diseño de Equipo , Femenino , Humanos , Masculino , Reproducibilidad de los ResultadosRESUMEN
Several recent studies have reported large intersubject variability of high-frequency thresholds measured with circumaural earphones. In the present study, high-frequency thresholds of 10 subjects were measured with circumaural (Sennheiser HD-250) and insert (Etymotic ER-1) earphones at 10, 12, 14, and 16 kHz. Overall results show significantly smaller variability of the threshold data obtained with insert earphones than with circumaural earphones. The above data indicate that insert earphones may be more suitable for high-frequency testing than circumaural earphones.
Asunto(s)
Amplificadores Electrónicos , Percepción Auditiva/fisiología , Audición/fisiología , Estimulación Acústica , Adolescente , Adulto , Umbral Auditivo , Diseño de Equipo , Femenino , Humanos , MasculinoRESUMEN
The aim of this study was to determine (a) if the speech importance noise detection threshold (SINDT) could be used as an accurate estimator of speech recognition threshold (SRT), and (b) whether the SINDT correlates well with various measures of the pure-tone threshold average (PTA). Pure-tone threshold, SRT, and SINDT tests were administered to 94 adults with various degrees of hearing loss. The results demonstrated that SRT can be accurately predicted from SINDT and that these two are highly correlated (r = 0.97). Since a SINDT measurement takes less time than SRT determination, the SINDT test may be recommended as an alternative for SRT in some applications.
Asunto(s)
Umbral Auditivo , Trastornos de la Audición/diagnóstico , Ruido , Percepción del Habla , Adolescente , Adulto , Anciano , Audiometría de Tonos Puros , Niño , Diseño de Equipo , Femenino , Pruebas Auditivas , Humanos , Recién Nacido , Masculino , Persona de Mediana EdadRESUMEN
One of the frequently quoted reasons for the rejection of hearing aids is amplification of background noise. The relationship between hearing aid use and toleration of background noise was assessed. Four groups of elderly subjects (at least 65 years old) and one group of young subjects with normal hearing participated in the study. Each group consisted of 15 subjects. The young subjects and elderly subjects in one group with relatively good hearing were tested for comparison with the hearing-impaired subjects. Elderly subjects in the three remaining groups had acquired hearing losses and had been fitted with hearing aids. The subjects were assigned to three groups on the basis of hearing aid use: full-time users, part-time users, and nonusers. The amount of background noise tolerated when listening to speech was tested. The speech stimulus was a story read by a woman and set at an individually chosen most comfortable level. The maskers were a babble of voices, speech-spectrum noise, traffic noise, music, and the noise of a pneumatic drill. There was a significant interaction between groups and noises. The full-time users tolerated significantly higher levels of music and speech-spectrum noise than part-time users and nonusers. In addition, the full-time users, but not the part-time users, assessed themselves as less handicapped in everyday functions when they wore hearing aids than when they did not wear their hearing aids.
Asunto(s)
Adaptación Psicológica , Audífonos/normas , Trastornos de la Audición/terapia , Ruido , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Comportamiento del Consumidor , Estudios de Evaluación como Asunto , Audífonos/psicología , Trastornos de la Audición/psicología , Humanos , Persona de Mediana Edad , MúsicaRESUMEN
Two effects of reverberation on the identification of consonants were evaluated for ten normal-hearing subjects: (1) the overlap of energy of a preceding consonant on the following consonant, called "overlap-masking"; and (2) the internal temporal smearing of energy within each consonant, called "self-masking." The stimuli were eight consonants/p,t,k,f,m,n,l,w/. The consonants were spoken in /s-at/context (experiment 1) and generated by a speech synthesizer in /s-at/ and/-at/contexts (experiment 2). In both experiments, identification of consonants was tested in four conditions: (1) quiet, without degradations; (2) with a babble of voices; (3) with noise that was shaped like either natural or synthetic/s/ for the two experiments, respectively; and (4) with room reverberation. The results for the natural and synthetic syllables indicated that the effect of reverberation on identification of consonants following/s/ was not comparable to masking by either the /s/ -spectrum-shaped noise or the babble. In addition, the results for the synthetic syllables indicated that most of the errors in reverberation for the /s-at/context were similar to a sum of errors in two conditions: (1) with /s/-shaped noise causing overlap masking; and (2) with reverberation causing self-masking within each consonant.
Asunto(s)
Enmascaramiento Perceptual , Sonido , Percepción del Habla/fisiología , Adulto , HumanosRESUMEN
Perceptual distances among single tokens of American English vowels were established for nonreverberant and reverberant conditions. Fifteen vowels in the phonetic context (b-t), embedded in the sentence "Mark the (b-t) again" were recorded by a male talker. For the reverberant condition, the sentences were played through a room with a reverberation time of 1.2 s. The CVC syllables were removed from the sentences and presented in pairs to ten subjects with audiometrically normal hearing, who judged the similarity of the syllable pairs separately for the nonreverberant and reverberant conditions. The results were analyzed by multidimensional scaling procedures, which showed that the perceptual data were accounted for by a three-dimensional vowel space. Correlations were obtained between the coordinates of the vowels along each dimension and selected acoustic parameters. For both conditions, dimensions 1 and 2 were highly correlated with formant frequencies F2 and F1, respectively, and dimension 3 was correlated with the product of the duration of the vowels and the difference between F3 and F1 expressed on the Bark scale. These observations are discussed in terms of the influence of reverberation on speech perception.
Asunto(s)
Fonética , Percepción del Habla/fisiología , Adolescente , Adulto , Humanos , Percepción de la Altura Tonal/fisiología , Pruebas de Discriminación del HablaRESUMEN
"Listening systems" are used for hearing impaired listeners as an alternative to public address systems (PA) used for the general public. These listening systems allow individual control of sound pressure level and minimize the effects of background noise and room reverberation. Three listening systems, based on an audio induction loop (AL), frequency modulation of radio frequencies (FM), and modulation of infrared light (IR) were compared among themselves and with a PA system in a medium-size classroom. Listening groups were normal hearing, hearing impaired, hearing aid users, and elderly. Word identification scores were obtained with the Modified Rhyme Test at two conditions: with a babble of 12 voices at a speech-to-noise ratio (S/N) of + 8 dB, and without the babble at S/N of +20 dB. Analysis of variance indicated that the main effects of systems, groups and room S/N were significant. Also significant were interactions of systems by groups, and systems by S/N. For all groups, the three listening systems provided better scores than the PA system. It can be concluded that all three of the tested listening systems are suitable for listeners with various degrees of hearing losses.
Asunto(s)
Audífonos , Pérdida Auditiva/fisiopatología , Auxiliares Sensoriales , Percepción del Habla , Estimulación Acústica , Anciano , Humanos , Rayos Infrarrojos , Presión , Radio , Estándares de Referencia , SonidoRESUMEN
The principles of designing an induction loop listening system are discussed. Step-by-step procedures for building an induction loop are presented. The loop described was installed in a medium-size classroom and listening tests were performed comparing the loop and loudspeakers. Two groups of hearing impaired listeners were used. One group of listeners wore hearing aids while the other group did not. Result indicated that for both groups, speech perception was enhanced with the loop system.