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Biomedical subjects

P G Stelmachowicz

Publications and source records attributed to P G Stelmachowicz.

At least 19 recordsLinked to original sources
PubMed1999

Subjective effects of peak clipping and compression limiting in normal and hearing-impaired children and adults.

Despite many advances in hearing-aid signal processing, compression limiting and peak clipping are still used. To date, perceptual studies have been conducted only with adults. The current study was designed to investigate the clarity of peak-clipped and compressed speech for both adults and children. Subjects were 30 normal-hearing and 30 hearing-impaired individuals in three age ranges (7-9, 10-12, and 16-50 years). Stimuli were processed at 60, 70, 75, and 80 dB SPL using peak clipping and at 80 dB SPL using compression limiting. Paired-comparison measures were used to assess the clarity of sentences, and a signal-to-distortion ratio (SDR) based on a measure of coherence between input and output was computed for each condition. For the peak-clipping conditions, there was a decrease in perceived clarity as the input increased from 60 to 80 dB SPL. This perceptual continuum was most apparent for the normal-hearing adults. The normal-hearing 10-12 year olds and the hearing-impaired adults showed a similar, but less pronounced, pattern. In contrast, the remaining three subject groups showed minimal differences in perceived clarity across conditions. Surprisingly, only the two oldest normal-hearing groups showed a clear preference for compression limiting over peak clipping at the highest input level, and only their results were consistent with the pattern of coherence across stimuli. Judgments of clarity by the normal-hearing subjects correlated best with the SDR in the 500-2000-Hz range, while clarity judgments of the hearing-impaired subjects correlated best with the SDR below 1000 Hz.

Adolescent↗
PubMed1999

Hearing aid outcome measures for children.

The provision of appropriate amplification for a young hearing-impaired child is critical as the aided speech signal will be used for the development of speech and language. The purpose of this paper is to provide an overview of the complex issues surrounding the documentation of hearing aid outcomes in the pediatric population. In the first two sections of the paper, the unique characteristics and needs of the pediatric population and factors complicating the measurement of outcome are described in detail. The third section provides a review of literature on existing outcome measures for children and the fourth section is devoted to a discussion of alternative approaches. The final section is an overview of clinical and research needs in the area of hearing aid outcome measures for children.

Child↗
PubMed1998

A comparison of threshold-based fitting strategies for nonlinear hearing aids.

OBJECTIVE: In recent years, wide dynamic range compression (WDRC) has been used with increasing success. To optimize the fit with this type of hearing aid circuitry, subjective measures of loudness growth often are used. Unfortunately, these type of measures cannot be performed with infants, young children, and some elderly individuals. The primary purpose of this study was to compare the fitting recommendations of two recently described threshold-based procedures for fitting nonlinear hearing aids (DSL 4.0 and FIG6) to the use gain settings of satisfied adult hearing aid users for whom the fitting was based on subjective measures of loudness growth. Because it cannot be assumed that the use settings for adults will be appropriate for young children, a secondary goal was to quantify the audibility of speech at the use settings derived from loudness growth measures. DESIGN: Forty-nine adult hearing aid users with mild to severe sensorineural hearing loss participated in this study. For all subjects, loudness growth measures were used to optimize the fit of a 2-channel WDRC hearing aid. The use gain at 50 and 80 dB SPL was compared with the gain recommended by DSL, FIG6, and the manufacturer's threshold-based fitting algorithm. RESULTS: In general, both DSL and FIG6 prescribed more gain than actually was used by these hearing aid wearers. These discrepancies increased as a function of frequency, and differences in excess of 20 dB were observed in some cases. The manufacturer's algorithm provided a closer approximation to the use gain than either DSL or FIG6. Utilizing these use gain values, an Aided Audibility Index (AAI) was calculated for soft, average, and loud speech across four degrees of hearing loss, ranging from mild to severe (12 conditions). Transfer functions for continuous discourse and nonsense syllables were applied to yield estimated intelligibility scores. For the higher context speech materials, estimated intelligibility was > or = 85% for nine of the 12 conditions. For low-context speech materials, estimated intelligibility was > or = 85% for only three of the 12 conditions. CONCLUSIONS: Results suggest that the gain recommendations provided by both DSL and FIG6 exceeded the gain actually used by the adult hearing-impaired subjects in this study. Gain recommendations from the manufacturer's algorithm provided a closer approximation to the use gain values of these subjects. These findings suggest that, for adult hearing aid users who cannot perform loudness judgments reliably, the manufacturer's algorithm would be expected to provide a closer approximation to loudness-based use gain values than either DSL or FIG6. However, AAI calculations revealed that the gain recommendations from this algorithm produce adequate audibility of speech only if one assumes linguistic competence. When AAI values are transformed to predict the intelligibility of low-context speech materials, it appears that the degree of audibility may not be appropriate for prelingually hearing-impaired children with more than a moderate hearing loss.

Aged↗
PubMed1996

Longitudinal study of FM system use in nonacademic settings: effects on language development.

OBJECTIVE: The overall objective of the present study was to assess the efficacy of FM system use in the home setting for a group of preschool children with mild-to-severe sensorineural hearing loss. Changes in language acquisition were monitored and compared with similar measures from a group of children who used hearing aids. Secondarily, the perceived benefits and practical problems associated with FM system use across a variety of nonacademic situations were documented. DESIGN: Ten children with mild-to-severe sensorineural hearing loss participated in a 2-yr longitudinal study investigating the efficacy of FM system use in the home setting. The subjects were divided into two groups: one group was instructed to use FM systems at home as often as possible while the other used only their personal hearing aids. Changes in language acquisition were monitored in both groups. Subjective benefit and the practical problems associated with use of FM systems outside of traditional academic environments were monitored via daily use logs, a weekly observation inventory, and a situational listening profile. RESULTS: The majority of children in both groups improved in all measures of language development over the study interval. Although there were relatively large individual differences in performance for some measures, no statistically significant differences between the FM and hearing aid users were found. However, some children in the FM group made unusually large gains in some aspects of language development over the study interval. In addition, both parents and children reported benefits of FM system use in specific listening situations. Throughout the 2-yr study, a number of practical problems associated with FM system use outside the classroom were identified. CONCLUSIONS: Formal language measures did not yield significant differences between the FM and HA groups, but some subjects had rates of language acquisition which suggested that FM system use may be beneficial in selected cases. In addition, subjective reports of FM system benefit suggest that appropriate use of the device may facilitate effective communication in a variety of listening situations. Although recent advances in FM system design may minimize some of the factors that reportedly restricted consistent FM use in this study, the complexities associated with the modes of operation and problems with FM interference remain issues that require consistent audiologic monitoring of FM system use in nonacademic environments.

Audiometry, Pure-Tone↗
PubMed1996

Measures of hearing aid gain for real speech.

OBJECTIVE: Non-speech stimuli typically are used to estimate the electroacoustic characteristics of a hearing aid. At present, there is no consensus as to what type of input stimulus will best represent the gain for real speech. The purpose of this study was to measure hearing aid gain using continuous discourse and to compare these values with gain measured with five different types of simpler stimuli. DESIGN: Hearing aid gain as a function of frequency was measured in a 2 cm3 coupler for 20 commercially available hearing aids. Circuitry included features such as linear peak clipping, compression limiting, 1-, 2-, and 3-channel full dynamic range compression, and adaptive compression. Input stimuli were a) 15 sec of continuous discourse, b) swept pure tones (SPTs), c) speech weighted composite noise (SWCN), d) simulated speech, e) speech weighted warble tones, and f) speech modulated noise. Input levels ranged from 50 to 80 dB SPL. RESULTS: In general, both SPTs and SWCN tended to underestimate the high-frequency gain for real speech. These discrepancies increased as a function of input intensity. On average, the SPT produced the greatest departure from the gain for real speech, producing differences for individual hearing aids as large as 10 to 14 dB. An analysis by circuit type revealed that discrepancies most likely occurred when a hearing aid was operating in a nonlinear mode. Of the five non-speech stimuli used, speech modulated noise and simulated speech seemed to provide the closest approximation to the gain measured with continuous discourse. CONCLUSIONS: When a hearing aid is operating in a nonlinear mode, non-speech stimuli will tend to underestimate the gain for real speech, particularly in the high frequencies. Under some conditions, these discrepancies may impact clinical decisions during the hearing aid fitting process. Additional studies are needed to elucidate the factors that contribute to the gain discrepancies observed in this study and to explore the use of additional stimuli (including short speech samples), which may result in better predictions of the gain for speech.

Correction of Hearing Impairment↗
PubMed1995

The perception of amplified speech by listeners with hearing loss: acoustic correlates.

Audibility-based approaches to hearing-aid selection generally have focused on the long-term average speech spectrum (LTASS). Advances in amplification technology (e.g., multiband signal processing, level-dependent frequency shaping, full dynamic range compression, adaptive compression) make it difficult to predict the audibility of short-term components of speech from the amplified LTASS. This study was designed to quantify the audibility of a specific phonemes as processed by two different hearing-aid circuits (linear and full dynamic range compression), and to investigate the relation between audibility and performance on a nonsense syllable recognition task. Data were obtained from three subjects with moderate sensorineural hearing loss. Nine unvoiced consonants were presented in two vowel contexts (/i/ and /a/) in both the pre- and post-vocalic position at three intensities. While the performance on selected conditions appeared to vary by hearing-aid type, only one subject showed a statistically significant difference between the two hearing-aid systems. Acoustic analyses revealed a variety of spectral and temporal changes to the speech signal following processing. Estimates of audibility were based upon each subject's thresholds and an acoustic analysis of the amplified signal that varied across phonemes and consonant position. A signal detection approach was used to predict performance from a simple measure of audibility.

Amplifiers, Electronic↗
PubMed1995

Case of recurrent, reversible, sudden sensorineural hearing loss in a child.

This paper describes audiologic, electrophysiologic, and medical test results for a now 10-year-old girl who has had 45 episodes of reversible, sudden sensorineural hearing loss over the last 8 years. Episodes have lasted from 6 to 72 hours and often have been accompanied by a mild illness. Acoustic immittance measures have been consistent with normal middle-ear function with the exception of absent ipsilateral and contralateral acoustic reflexes. Mechanically evoked perioral reflex activity was markedly asymmetric following lower lip stimulation. The asymmetry of R1 activation between right and left side lower lip inputs raises questions about the integrity of central connections within the brain stem, including internuncial pathways coursing between trigeminal sensory relay nuclei and the facial motor nucleus. An electrocochleographic evaluation revealed cochlear microphonic but absent or markedly abnormal whole nerve action potentials. Auditory brainstem responses (ABR) have been either absent or poorly formed and significantly delayed, regardless of hearing sensitivity. Middle and late auditory evoked potentials were essentially normal. Both transient-evoked and distortion-product otoacoustic emissions were present regardless of peripheral auditory sensitivity. All medical tests have been essentially normal. Although no definitive diagnosis has been reached, beta blockers have been used with some success. Taken together, these data document a very unusual case of fluctuating hearing loss. The electrocochleographic and otoacoustic emission data suggest that the outer hair cells are functioning normally and that the loss is not cochlear in origin.(ABSTRACT TRUNCATED AT 250 WORDS)

Audiometry, Evoked Response↗
PubMed1994

Preferred hearing-aid frequency responses in simulated listening environments.

This study was designed to determine if an adaptive strategy could be used to select frequency/gain characteristics that would be considered appropriate across a variety of listening environments. In Experiment I, the test-retest reliability of the paired comparison procedure used in Experiment II was assessed in quiet for nine subjects and in speech noise for six subjects. For both conditions, results revealed mean standard deviations of < 3 dB from 200 through 4000 Hz. In Experiment II, four subjects selected frequency/gain characteristics for five different listening environments (quiet, speech noise, quiet conference room, reverberant lecture hall, and reverberant lecture hall in noise). In general, subjects did not tend to select different frequency/gain characteristics across the five simulated environments used in this study. When differences in frequency responses were observed, they tended to be alterations in overall gain rather than changes in relative frequency response. Findings support additional evaluation in more diverse listening environments, possibly with systems that incorporate nonlinear signal processing.

Acoustic Stimulation↗
PubMed1993

Real ear to 6-cm3 coupler differences in young children.

Real-ear sound pressure levels under supra-aural earphones were measured for a group of young children (9 months to 7 years) and adults. Pure-tone signals were presented at nine test frequencies from 250 to 6000 Hz, and real ear to 6-cm3 coupler differences were computed for each frequency. Results suggest that, by 2 years of age, average real ear to 6-cm3 coupler differences are similar for adults and children. The intersubject variability for all groups supports the need for real-ear threshold measures on an individual basis in cases where the ability to amplify the speech spectrum to a level that is audible across the frequency range is in question.

Acoustics↗
PubMed1993

Long-term and short-term characteristics of speech: implications for hearing aid selection for young children.

This study examined the effects of distance and postural position of both parents and children on the long-term and short-term spectral characteristics of speech produced by the parents. Thirty children (ages 2 months to 3 1/2 years) and their parents (30 mothers and 15 fathers) participated. Third-octave band and overall levels of the long-term average speech spectrum (LTASS) for each speech sample were analyzed in three postural positions and a 1-meter reference condition for each age category. Short-term spectral characteristics of three phonemes (/s/, /integral of/, /t integral of/) also were analyzed. Results show that typical levels at the input to a child's hearing aid microphone may be as much as 20 dB higher than those found in face-to-face adult conversation. Furthermore, the spectral shape may deviate substantially from an idealized version of the LTASS. Results of the short-term analysis reveal that the peak levels of the three selected phonemes often exceed the LTASS by more than the 12 dB that is often quoted to represent the 1% rms levels of speech in relation to the long-term average. Implications of these results for specific hearing losses are discussed.

Acoustic Stimulation↗
PubMed1992

Coupling of FM systems to individuals with unilateral hearing loss.

This study examined the attenuation characteristics of five FM system sound delivery options for a group of 10 adults and 15 children (5-13 years). Sound delivery options included a tube-fitting, lightweight headphones, a CROS earmold with tubing, a CROS earmold with a snap-ring, and a standard snap-ring earmold with a vent. Attenuation was defined as the difference between probe-tube microphone measures of the ear canal resonance and the SPL in the ear canal with each sound delivery option in place. A statistically significant but clinically inconsequential difference in attenuation for the CROS earmold with tubing was noted between adults and children. No significant differences in attenuation for any of the other sound delivery options were noted between adults and children. An investigation of the relationship between magnitude of attenuation and percentage of the ear canal occluded suggests that degree of occlusion is a major factor in determining degree of attenuation provided by a particular sound delivery option. Results also indicate that significant attenuation of high-frequency signals can occur with earmolds commonly considered nonoccluding. Caution should be used in fitting hearing aids or FM systems to individuals with normal high-frequency hearing sensitivity to prevent attenuation of unamplified high-frequency speech information.

Adult↗
PubMed1992

Equivalent ear canal volumes in children pre- and post-tympanostomy tube insertion.

Pre- and postoperative equivalent ear canal volume measures were obtained from a group of 334 children ranging in age from 6 weeks to 6.7 years. The purpose of the study was to develop volumetric guidelines for the determination of tympanostomy tube patency. For children 4 years and older, almost no ambiguity existed in making this determination accurately. For younger children, the pre- and postoperative distributions overlap. A criterion value of greater than or equal to 1.0 cm3 as an indicator of a tympanic membrane perforation appears to yield the lowest possible error rate. When both pre- and postoperative measures are available, a difference of greater than or equal to 0.4 cm3 can be used in conjunction with the absolute value to identify a patent tympanostomy tube.

Acoustic Impedance Tests↗
PubMed1991

Evaluation and assessment of FM systems.

In the past, frequency modulated (FM) systems were recommended for use only in educational settings for children with severe or profound hearing losses. Recent studies, however, have suggested that FM systems may be appropriate in nonacademic settings and also may benefit children with minimal hearing loss. In addition to the more widespread application of FM use, advances in amplification technology have provided audiologists with a variety of devices and coupling options, resulting in more variables to evaluate in the fitting process. There are three commonly used methods of evaluating FM systems: functional gain measures, probe tube microphone measures, and coupler measures. This paper is intended to provide the audiologist working with FM systems with an overview of the complexities involved in selecting and setting FM systems and the benefits and limitations of each evaluation method. Each evaluation method is examined in view of how well it answers three basic questions related to frequency response, maximum output, and distortion in FM systems. Finally, other issues which may impact on the selection of an FM system for a given individual are discussed.

Acoustics↗
PubMed1991

Relevant factors in the identification of hearing loss.

This study examined factors which may affect early identification of hearing loss. The medical records of 123 children with educationally significant hearing impairment were examined. Information about each child's degree and type of hearing loss, etiology, referral source, birth and medical history, additional handicaps, age of suspicion of loss, mode of identification, age of identification, and age at which aided was entered into a database for further analysis. The age range for identification was 7 weeks to 10 yr, with a median age of 2.1 yr. Children with a greater degree of hearing loss, an additional handicap, additional medical conditions, or an etiology strongly associated with hearing loss were identified earlier than those without these factors. Unexpectedly, children with a history of middle ear dysfunction were identified no later than those without, and children with a positive family history of hearing loss were identified later than those with a negative family history. These results agree with other studies which show that, in general, children are identified and habilitated at a later age than that recommended by both the American Speech-Language-Hearing Association Committee and the Joint Committee on Infant Hearing.

Age Factors↗
PubMed1991

Localization ability in infants with simulated unilateral hearing loss.

This study investigated the feasibility of using a localization task to rule out unilateral hearing loss in infants. Fourcorner localization ability was assessed in 29 normal-hearing infants (9-20 mo) using four different test stimuli. In these same infants, a mild unilateral hearing loss was simulated by occlusion of the external auditory canal and the test sequence was repeated. Analysis of front-back, right-left, and combined errors for each of the test stimuli revealed that this type of task may allow detection of unilateral hearing loss as slight as 25 dB HL.

Acoustic Stimulation↗
PubMed1990

Speech perception in low-pass filtered noise for normal and hearing-impaired listeners.

Two experiments were conducted concerning speech perception in noise. In Experiment 1, a comparison was made between adaptive and fixed-level procedures to estimate the S/N ratio at which 50% correct performance occurred for nonsense syllables for normal-hearing listeners. The two methods yield similar S/N ratio estimates, but the consonant confusions found with the fixed-level method could not be predicted accurately from the adaptive procedure. In Experiment 2, the adaptive procedure was used to estimate the S/N ratio for a 50% performance level in low-pass filtered noise with a range of cutoff frequencies. Data were obtained from 5 normal-hearing listeners at two speech levels (50 and 75 dB SPL) and 4 hearing-impaired listeners at one speech level (75 dB SPL). The hearing-impaired listeners required a better S/N ratio than the normal listeners at either presentation level for all except the widest bandwidth, where their S/N ratios began to converge with the normal values. In addition, the S/N ratios for the hearing-impaired listeners plateaued at relatively narrow bandwidths (0.75 to 2.5 kHz) compared to the normal-hearing group (3.0 to 5.0 kHz). That is, the addition of high-frequency components to the noise did not alter performance. These findings suggest that the hearing-impaired listeners may have relied upon either low-frequency cues or prosodic cues in the perception of these test items.

Adaptation, Physiological↗
PubMed1990

Complex and pure-tone signals in the evaluation of hearing-aid characteristics.

In recent years, a number of commercially available systems have been developed to analyze the electroacoustic characteristics of hearing aids. In addition to pure-tone signals, these systems often use a wide variety of complex signals such as broadband noise, clicks, and multitonal complexes. In this paper, a number of practical and theoretical issues concerning the use of pure-tone and complex signals in the evaluation of hearing-aid characteristics are described. The circumstances under which discrepancies in estimated gain and maximum output might occur using these two types of signals are described and the clinical implications of these differences are discussed.

Algorithms↗