Patrick N. Plyler

Effects of age and spectral shaping on perception and neural representation of stop consonant stimuli

OBJECTIVE To determine if (1) aging affects neural representation of a dynamic spectral speech cue and (2) spectrally-shaped gain applied to the cue reduces any aging effects. METHODS Psychometric functions and cortical evoked responses were compared in young and older listeners with normal hearing. Stimuli were consonant-vowels along a /bdg/ place-of-articulation continuum in an unshaped and shaped condition. Shaped stimuli enhanced audibility of the F2 formant transition relative to the rest of the stimulus. RESULTS Compared with younger listeners, older listeners had larger /d/ categories, longer P2 latencies, and larger N1 amplitudes to unshaped stimuli. To shaped stimuli, older listeners had /d/ categories and P2 latencies more similar to those measured from younger listeners, while N1 amplitudes were larger. CONCLUSIONS Aging significantly affects the processing of dynamic spectral information. For some measures, differences due to aging were minimized with spectrally-shaped stimuli. SIGNIFICANCE Aging reduces neural responsiveness to dynamic spectral cues. If the cue is enhanced, neural responsiveness is increased and perceptual measures are more like those from the younger listeners for some stimuli. This suggests that aging may decrease responsiveness of intact neurons as opposed to destroying neurons and/or distorting spectral coding.

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.

Effects of hearing loss and spectral shaping on identification and neural response patterns of stop-consonant stimuli

In order to determine the effects of hearing loss and spectral shaping on a dynamic spectral speech cue, behavioral identification and neural response patterns of stop-consonant stimuli varying along the /b-d-g/ place-of-articulation continuum were measured from 11 young adults (mean age = 27 years) and 10 older adults (mean age = 55.2 years) with normal hearing, and compared to those from 10 older adults (mean age = 61.3 years) with mild-to-moderate hearing impairment. Psychometric functions and N1-P2 cortical evoked responses were obtained using consonant-vowel (CV) stimuli with frequency-independent (unshaped) amplification as well as with frequency-dependent (shaped) amplification that enhanced F2 relative to the rest of the stimulus. Results indicated that behavioral identification and neural response patterns of stop-consonant CVs were affected primarily by aging and secondarily by age-related hearing loss. Further, enhancing the audibility of the F2 transition cue with spectrally shaped amplification partially reduced the effects of age-related hearing loss on categorization ability but not neural response patterns of stop-consonant CVs. These findings suggest that aging affects excitatory and inhibitory processes and may contribute to the perceptual differences of dynamic spectral cues seen in older versus young adults. Additionally, age and age-related hearing loss may have separate influences on neural function.

The Effects of Receiver Placement on Probe Microphone, Performance, and Subjective Measures with Open Canal Hearing Instruments

BACKGROUND Open canal hearing instruments differ in method of sound delivery to the ear canal, distance between the microphone and the receiver, and physical size of the devices. Moreover, RITA (receiver in the aid) and RITE (receiver in the ear) hearing instruments may also differ in terms of retention and comfort as well as ease of use and care for certain individuals. What remains unclear, however, is if any or all of the abovementioned factors contribute to hearing aid outcome. PURPOSE To determine the effect of receiver location on performance and/or preference of listeners using open canal hearing instruments. RESEARCH DESIGN An experimental study in which subjects were exposed to a repeated measures design. STUDY SAMPLE Twenty-five adult listeners with mild sloping to moderately severe sensorineural hearing loss (mean age 67 yr). DATA COLLECTION AND ANALYSIS Participants completed two six-week trial periods for each device type. Probe microphone, objective, and subjective measures (quiet, noise) were conducted unaided and aided at the end of each trial period. RESULTS Occlusion effect results were not significantly different between the RITA and RITE instruments; however, frequency range was extended in the RITE instruments, resulting in significantly greater maximum gain for the RITE instruments than the RITA instruments at 4000 and 6000 Hz. Objective performance in quiet or in noise was unaffected by receiver location. Subjective measures revealed significantly greater satisfaction ratings for the RITE than for the RITA instruments. Similarly, preference in quiet and overall preference were significantly greater for the RITE than for the RITA instruments. CONCLUSIONS Although no occlusion differences were noted between instruments, the RITE did demonstrate a significant difference in reserve gain before feedback at 4000 and 6000 Hz. Objectively; no positive benefit was noted between unaided and aided conditions on speech recognition tests. These results suggest that such testing may not be sensitive enough to determine aided benefit with open canal instruments. However, the subjective measures (Abbreviated Profile of Hearing Aid Benefit [APHAB] and subjective ratings) did indicate aided benefit for both instruments when compared to unaided. This further suggests the clinical importance of subjective measures as a way to measure aided benefit of open-fit devices.

Treatment of objective and subjective benign paroxysmal positional vertigo.

BACKGROUND Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo in adults and is a result of otolithic particles or debris that become free floating within a semicircular canal or adhere to the cupula. Characteristics of BPPV include brief episodes of latent onset vertigo that occur with changes in head position, transient rotary nystagmus beating toward the dependent ear, and reversed nystagmus upon sitting up. Both the vertigo and nystagmus fatigue quickly while maintaining the same head position. The BPPV may be classified as objective or subjective. Objective BPPV presents all the aforementioned symptoms whereas subjective BPPV presents all the symptoms without nystagmus. The accepted method of treatment for objective BPPV is canalith repositioning maneuvers (CRM); however, CRM are not traditionally used as the method of treatment for cases of subjective BPPV. PURPOSE The purpose of the study was to determine if the subjective report of dizziness using the Dizziness Handicap Inventory (DHI) was different in patients with objective and subjective BPPV and to determine if the two groups showed similar improvements in perceived dizziness handicap following CRM treatment. RESEARCH DESIGN The present study utilized a retrospective, repeated measures design. STUDY SAMPLE Sixty-three adults with BPPV that were given the DHI both before and after CRM treatment. DATA COLLECTION AND ANALYSIS Pre and post DHI results were analyzed for participants with objective versus subjective BPPV. A five-question DHI subscale was also analyzed between the groups. RESULTS A significant difference was noted between initial and posttreatment DHI scores for patients in both the subjective and objective groups when using the full-scale and subscale DHI. No significant difference was noted between groups for their initial or posttreatment DHI scores. The two groups also did not differ significantly in their initial or posttreatment DHI subscale scores. CONCLUSIONS The results of the study indicated that individuals with both objective and subjective BPPV demonstrated significant improvement in DHI scores following CRM treatment. Additionally, there was no difference in DHI improvement for the subjective versus objective group suggesting CRM are effective for both subjective BPPV and objective BPPV. This improvement in DHI scores was also noted in the five-question DHI subscale with no significant difference noted between groups. These findings combined with previous studies suggest the presence or absence of nystagmus during Dix-Hallpike maneuvers is not related to the effectiveness of treatment using CRM.

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.

The effects of noise reduction technologies on the acceptance of background noise.

BACKGROUND Directional microphones (D-Mics) and digital noise reduction (DNR) algorithms are used in hearing aids to reduce the negative effects of background noise on performance. Directional microphones attenuate sounds arriving from anywhere other than the front of the listener while DNR attenuates sounds with physical characteristics of noise. Although both noise reduction technologies are currently available in hearing aids, it is unclear if the use of these technologies in isolation or together affects acceptance of noise and/or preference for the end user when used in various types of background noise. PURPOSE The purpose of the research was to determine the effects of D-Mic, DNR, or the combination of D-Mic and DNR on acceptance of noise and preference when listening in various types of background noise. RESEARCH DESIGN An experimental study in which subjects were exposed to a repeated measures design was utilized. STUDY SAMPLE Thirty adult listeners with mild sloping to moderately severe sensorineural hearing loss participated (mean age 67 yr). DATA COLLECTION AND ANALYSIS Acceptable noise levels (ANLs) were obtained using no noise reduction technologies, D-Mic only, DNR only, and the combination of the two technologies (Combo) for three different background noises (single-talker speech, speech-shaped noise, and multitalker babble) for each listener. In addition, preference rankings of the noise reduction technologies were obtained within each background noise (1 = best, 3 = worst). RESULTS ANL values were significantly better for each noise reduction technology than baseline; and benefit increased significantly from DNR to D-Mic to Combo. Listeners with higher (worse) baseline ANLs received more benefit from noise reduction technologies than listeners with lower (better) baseline ANLs. Neither ANL values nor ANL benefit values were significantly affected by background noise type; however, ANL benefit with D-Mic and Combo was similar when speech-like noise was present while ANL benefit was greatest for Combo when speech spectrum noise was present. Listeners preferred the hearing aid settings that resulted in the best ANL value. CONCLUSION Noise reduction technologies improved ANL for each noise type, and the amount of improvement was related to the baseline ANL value. Improving an ANL with noise reduction technologies is noticeable to listeners, at least when examined in this laboratory setting, and listeners prefer noise reduction technologies that improved their ability to accept noise.

The subjective evaluation of the expansion time constant in single-channel wide dynamic range compression hearing instruments

The present study investigated the subjective evaluation of expansion time constants in single-channel wide dynamic range compression (WDRC) hearing instruments. Thirty participants utilized binaural WDRC hearing instruments for a two-week trial. Subjective evaluations were conducted by having each participant rate their satisfaction with the expansion time constant on a daily basis and by having each participant indicate their preferred expansion time constant following the completion of the two-week trial. Each change in expansion time constant significantly affected listener satisfaction; however, all time constants resulted in satisfactory performance. Of the users expressing a preference, 75% preferred fast-acting over slow-acting expansion. These findings suggest that dynamic expansion parameters play an important role in determining the effectiveness of the feature for a given listener.

Effects of hearing loss and spectral shaping on identification and neural response patterns of stop-consonant stimuli in young adults

Objectives: The primary purpose of this study was to more clearly define the effects of hearing loss, separate from age, on perception, and neural response patterns of dynamic spectral cues. To do this, the study was designed to determine whether (1) hearing loss affects the neural representation and/or categorical perception of stop-consonant stimuli among young adults and (2) spectrally shaped amplification aimed at increasing the audibility of the F2 formant transition cue reduces any effects of hearing loss. It was predicted that (1) young adults with hearing loss would differ from young adults with normal hearing in their behavioral and neural responses to stop-consonant stimuli and (2) enhancing the audibility of the F2 formant transition cue relative to the rest of the stimulus would not overcome the effects of hearing loss on behavioral performance or neural response patterns. Design: Behavioral identification and neural response patterns of stop-consonant stimuli varying along the /b-d-g/ place-of-articulation continuum were measured from seven young adults with mild-to-moderate hearing impairment (mean age = 21.4 yr) and compared with responses from 11 young adults with normal hearing (mean age = 27 yr). Psychometric functions and N1-P2 cortical-evoked responses were evoked by consonant-vowel (CV) stimuli without (unshaped) and with (shaped) frequency-dependent amplification that enhanced F2 relative to the rest of the stimulus. Results: Behavioral identification and neural response patterns of stop-consonant CVs differed between the two groups. Specifically, to the unshaped stimuli, listeners with hearing loss tended to make low-frequency judgments more often (more /b/, fewer /g/) than listeners with normal hearing when categorizing along the /b-d-g/ continuum. Additionally, N1 amplitudes were larger and P2 latencies were longer to all phonemes in young adults with hearing impairment versus normal hearing. Enhancing the audibility of the F2 transition cue with spectrally shaped amplification did not alter the neural representation of the stop-consonant CVs in the young listeners with hearing loss. It did modify categorical perception such that listeners with hearing loss tended to make high-frequency judgments more often (more /g/, fewer /b/). However, shaping the stimuli did not make their psychometric functions more like those of the normal controls. Instead, young adults with hearing loss went from one extreme (low-frequency judgments with unshaped stimuli) to the other (high-frequency judgments with shaped stimuli), whereas judgments from the normal controls were more balanced. Conclusions: Hearing loss, separate from aging, seems to negatively impact identification and neural representation of time-varying spectral cues like the F2 formant transition. Enhancing the audibility of the F2 formant transition cue relative to the rest of the stimulus does not overcome the effects of hearing loss on behavioral performance or neural response patterns in young adults. Thus, the deleterious effects of hearing loss on stop-consonant perception along the place-of-articulation continuum may not only be due solely to decreased audibility but also due to improper coding by residual neurons, resulting in distortion of the time-varying spectral cue. This may explain, in part, why amplification cannot completely compensate for the effects of sensorineural hearing loss.

Comparison of Multichannel Wide Dynamic Range Compression and ChannelFree Processing in Open Canal Hearing Instruments

BACKGROUND Multichannel wide dynamic range compression (WDRC) and ChannelFree processing have similar goals yet differ significantly in terms of signal processing. Multichannel WDRC devices divide the input signal into separate frequency bands; a separate level is determined within each frequency band; and compression in each band is based on the level within each band. ChannelFree processing detects the wideband level, and gain adjustments are based on the wideband signal level and adjusted up to 20,000 times per second. Although both signal processing strategies are currently available in hearing aids, it is unclear if differences in these signal processing strategies affect the performance and/or preference of the end user. PURPOSE The purpose of the research was to determine the effects of multichannel wide dynamic range compression and ChannelFree processing on performance and/or preference of listeners using open-canal hearing instruments. RESEARCH DESIGN An experimental study in which subjects were exposed to a repeated measures design was utilized. STUDY SAMPLE Fourteen adult listeners with mild sloping to moderately severe sensorineural hearing loss participated (mean age 67 yr). DATA COLLECTION AND ANALYSIS Participants completed two 5 wk trial periods for each signal processing strategy. Probe microphone, behavioral and subjective measures were conducted unaided and aided at the end of each trial period. RESULTS Behavioral and subjective results for both signal processing strategies were significantly better than unaided results; however, behavioral and subjective results were not significantly different between the signal processing strategies. CONCLUSIONS Multichannel WDRC and ChannelFree processing are both effective signal processing strategies that provide significant benefit for hearing instrument users. Overall preference between the strategies may be related to the degree of hearing loss of the user, high-frequency in-situ levels, and/or acceptance of background noise.