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Biomedical subjects

R C Seewald

Publications and source records attributed to R C Seewald.

At least 19 recordsLinked to original sources
PubMed2000

Comparison of linear gain and wide dynamic range compression hearing aid circuits II: aided loudness measures.

OBJECTIVES: The goal of this study was to test the theoretical advantages of a single-channel wide dynamic range compression (WDRC) circuit fitted using the DSL method for increased dynamic range and normalized loudness growth. DESIGN: Ten adolescents and young adults with moderate to severe sensorineural hearing loss were fitted monaurally with the Siemens Viva 2 Pro behind-the-ear instrument set to DSL 4.0 targets for both linear gain and WDRC processing. Threshold, upper limit of comfort and loudness growth were measured in the unaided, linear gain and WDRC conditions for warble tones, environmental sounds and speech. Twelve adult listeners with normal hearing also were tested monaurally in the unaided condition to provide normative data for comparison purposes. RESULTS: The WDRC hearing aid provided a greater input dynamic range than the linear circuit for all stimuli. The dynamic range was normalized for more subjects with the WDRC than the linear hearing aid. In addition, exponential loudness growth functions fitted to the loudness growth data showed that, on average, loudness growth was more normalized with the WDRC hearing aid fitted to DSL[i/o] targets than the linear hearing aid fitted to DSL[i/o] targets. CONCLUSIONS: WDRC processing, fitted using the DSL[i/o] method, has potential applications in hearing aid fittings for listeners with moderate to severe hearing loss because it provides an audible, comfortable and tolerable amplified signal across a wider range of inputs than linear gain processing, without the need for volume control adjustments.

Adolescent↗
PubMed2000

Speech recognition with in-the-ear and behind-the-ear dual-microphone hearing instruments.

The primary purpose of this study was to compare the overall listening benefit in diffuse noise provided by dual-microphone technology in an in-the-ear (ITE) hearing instrument to that provided by dual-microphone technology in a behind-the-ear (BTE) hearing instrument. Further, the study was designed to determine whether the use of the dual-microphone + the manufacturer's party response algorithm in the ITE and BTE hearing instruments provided listening benefit in diffuse noise over their respective omnidirectional microphone modes. Twenty-four adults with mild to moderately severe sensorineural hearing loss were evaluated while wearing binaural BTE and ITE hearing instruments. The results indicated that the dual-microphone + party response mode did provide significant benefit in diffuse noise for both the ITE (3.27 dB signal-to-noise ratio [SNR] improvement) and BTE (5.77 dB SNR improvement) hearing instruments relative to their respective conventional omnidirectional microphones. No significant difference in performance was found between the ITE and BTE hearing instruments when each device was in the dual-microphone + party response mode. It is concluded that the use of dual-microphone technology in both ITE and BTE hearing instruments can improve speech recognition in diffuse noise.

Adult↗
PubMed2000

Preferred listening levels of children who use hearing aids: comparison to prescriptive targets.

The preferred listening levels (PLLs) of children with sensorineural hearing loss were elicited using conversation-level speech, heard through the children's own hearing aids. All hearing aids were fitted using the desired sensation level (DSL) method. Comparisons were made between the PLL and targets from the following prescriptive formulae: DSL version 4.1 and two versions of the National Acoustic Laboratories (NAL) procedure, including NAL revised for severe-profound losses (NAL)-RP and NAL nonlinear NAL/NL1. Results for this sample of children indicated that the PLL was similar to the DSL targets, and that, on average, NAL-RP/NL1 targets recommended less gain than that preferred by the majority of children in this study. The implications of factors such as acclimatization, test levels, and clinical procedures on these results are discussed.

Adolescent↗
PubMed1999

Predictive validity of a procedure for pediatric hearing instrument fitting.

In 1994, Moodie, Seewald, & Sinclair described the development of a clinical procedure for predicting real-ear hearing instrument performance in young children. The purpose of the present study was to determine the validity of this procedure for predicting the real-ear aided gain (REAG) and real-ear saturation response (RESR) of hearing instruments worn by children. To this end, both the REAG and RESR were measured, through probe-microphone measures, and predicted, using the Moodie et al. procedure. The findings confirmed that the 2-cc coupler-based procedure, with individualized acoustic transforms, described by Moodie et al., resulted in highly accurate predictions of real-ear hearing instrument performance for both REAG and RESR at five test frequencies. The implications of these findings for the clinical fitting of hearing instruments in infants and young children are discussed.

Acoustic Stimulation↗
PubMed1999

Comparison of linear gain and wide dynamic range compression hearing aid circuits: aided speech perception measures.

OBJECTIVES: The goal of this study was to test the theoretical advantages of a single-channel wide dynamic range compression (WDRC) circuit for speech intelligibility and loudness comfort for five speech spectra. DESIGN: Twelve adolescents and young adults with moderate to severe hearing loss were fitted with the Siemens Viva 2 Pro behind-the-ear instrument set to DSL 4.0 targets for both linear gain and WDRC processing. Speech intelligibility was measured in the unaided, linear gain and WDRC conditions using two tasks in quiet: nonsense words and sentences. The items were digitally filtered to represent five speech spectra: average speech at 4 m, average speech at 1 m, own voice at ear level, classroom at 1 m, and shouted speech at 1 m. The subjects also rated the loudness of each hearing aid/speech spectrum combination using a categorical rating scale. RESULTS: Both the linear gain and WDRC settings provided improved speech recognition relative to the unaided condition, and the two circuits resulted in equivalent performance for average speech input levels. On average, the WDRC aid resulted in high and uniform speech recognition scores across the five spectra. In contrast, the linear gain aid resulted in a lower recognition score for soft speech and shouted speech relative to that obtained with an average speech level. Analysis of individual speech recognition benefit scores revealed that 11 out of 12 subjects had equal or greater performance with the WDRC processing than the linear processing. Subjective loudness ratings in the linear gain condition were compatible with decreased sensation level for soft speech and loudness discomfort for shouted speech. CONCLUSIONS: WDRC processing has potential applications in hearing aid fittings for listeners with moderate to severe hearing loss because it provides a consistently audible and comfortable signal across a wide range of listening conditions in quiet without the need for volume control adjustments.

Adolescent↗
PubMed1998

Validity and repeatability of level-independent HL to SPL transforms.

OBJECTIVE: The purpose of this study was to evaluate the reliability and validity of the real ear to coupler difference (RECD) and the real ear to dial difference (REDD) in predicting real ear SPL (RESPL). DESIGN: The RESPL, RECD, and REDD were measured in the right ear of 24 normal-hearing subjects using probe microphone equipment and both insert and supra-aural earphones. The phones and probe tube were removed and replaced, and the RECD and REDD were remeasured. RESULTS: RESPL was predicted using the RECD for insert earphone data and the REDD for supra-aural earphone data. Reliability estimates were calculated as the difference between test and retest values for the RECD and REDD. Validity estimates were calculated as the difference between measured and predicted RESPL. Results indicate that the RECD and REDD have equal and high reliability and validity in predicting RESPL. CONCLUSIONS: It is concluded that the RECD and REDD may be used as level-independent HL to SPL transforms as a substitute for in situ audiometric procedures.

Adult↗
PubMed1998

Procedural considerations in the real-ear measurement of completely-in-the-canal instruments.

Conventional procedures for measurement of the real-ear aided response (REAR) of hearing aids are performed by placing the probe tube 5 mm beyond the medial tip of the canal portion of the earmold or shell and within 5 mm of the tympanic membrane. Completely-in-the-canal (CIC) instruments insert more deeply into the ear canal, and thus may make adherence to conventional probe-microphone procedures impossible. The REAR was measured at several probe tube insertion depths, using two insertion methods: through a probe vent and alongside the CIC shell. Results indicated that conventional probe insertion depth is not necessary for CIC instruments and may place some clients at risk for discomfort due to contact of the probe tube with the tympanic membrane. Placement of the probe tube along-side the CIC shell rather than through a probe vent resulted in slit leak venting effects that were highly variable across subjects. A probe tube placement protocol for use with CIC instruments is suggested.

Adult↗
PubMed1997

Field-to-microphone transfer functions for completely-in-the-canal (CIC) instruments.

OBJECTIVE: To measure the field-to-microphone transfer function for two sizes of completely-in-the-canal (CIC) devices, at two loudspeaker azimuths. DESIGN: Field-to-microphone transfer functions were measured for both standard- and micro-CIC instruments, at 0 degree and 45 degrees azimuth, in a sample of 24 adults. This was accomplished with custom instruments, which allowed for a direct connection between the CIC microphone electrical output and the measurement/analysis instrumentation system. RESULTS: For the standard-CIC, the peak in the average field-to-microphone transfer function was 8 dB at 4000 Hz for 0 degree azimuth and 13.7 dB at 5000 Hz for 45 degrees azimuth. CONCLUSIONS: The results demonstrate and define, at two signal azimuths, the acoustic advantage of the CIC microphone placement relative to that reported for alternative hearing aid styles.

Adult↗
PubMed1997

Effects of test procedure on individual loudness functions.

OBJECTIVE: To determine if measurement procedure effects occur for loudness perception data measured using a categorical rating scale. DESIGN: Loudness data were obtained from 40 normal-hearing adult volunteers, using 30 levels of pure tones at four frequencies (500, 1000, 2000, and 4000 Hz), with judgments made on a 9-point categorical scale. Two presentation orders, random and sequential, were compared within subjects. Subjects were divided into two groups: one group heard only a single tone on every trial, whereas the other group was presented with a maximum level reference tone at the start of each trial. RESULTS: A significant difference was found between loudness function exponents measured with the random and sequential presentation order of stimulus level. A significant difference was found between loudness function exponents measured when a high-level referent was presented at the start of each trial. The sequential presentation order was further subdivided into ascending and descending runs, and the loudness function exponents for each run were examined separately. The results showed a significant interaction between sequence (ascending versus descending) and group. CONCLUSIONS: For normal-hearing listeners, the procedure used to measure loudness has an effect on the loudness function exponent obtained. These results appear to be related to stimulus context effects. Loudness function exponents are smaller when the stimulus is preceded by a stimulus level greater than the level of the test tone. This occurred when a high-level referent was presented at the start of each trial or when the stimulus level from the previous trial was greater than the test level, as in a descending run. It seems likely that the difference between loudness function exponents obtained with a random and sequential presentation of level can be explained by the same phenomenon. The significance of these results for hearing aid fittings in which loudness normalization is the goal is discussed.

Auditory Threshold↗
PubMed1995

The input/output formula: a theoretical approach to the fitting of personal amplification devices.

There is a growing trend for hearing aids to incorporate wide dynamic range compression. The input/output (I/O) hearing aid formula, presented in this report, is a general frequency-specific mathematical approach which describes the relationship between the input level of a signal delivered to a hearing aid and the output level produced by the hearing aid. The I/O formula relates basic psychoacoustic parameters, including hearing threshold level and uncomfortable listening level, to the electroacoustic characteristics of hearing aids. The main design goal of the I/O formula was to fit the acoustic region corresponding to the "extended" normal auditory dynamic range into the hearing-impaired individual's residual auditory dynamic range. The I/O approach can be used to fit hearing aids utilizing linear gain, linear compression or curvilinear compression to a hearing-impaired individual's residual auditory area.

Auditory Threshold↗
PubMed1992

Comparison of two methods for estimating the sensation level of amplified speech.

Several methods have been proposed to estimate the sensation level (SL) at which children receive amplified speech from their hearing aids. The present study compared the SL estimates obtained with two such methods: (1) a sound field aided audiogram approach, and (2) an electroacoustic approach that incorporated the use of a probe tube microphone system (Seewald, Ross, & Stelmachowicz, 1987). Sound field aided thresholds were obtained for 13 hearing-impaired subjects at eight audiometric frequencies. For the electroacoustic approach, in situ thresholds were obtained using a button-type hearing aid receiver attached to a custom earmold. Real ear aided responses were measured using a 70 dB RMS speech-weighted composite noise signal (Frye, 1986). A comparison of the frequency-specific SL estimates derived from the two different methods revealed that the sound field aided audiogram approach yielded higher SL estimates for 74% of the individual comparisons. A detailed analysis of the findings obtained from two subjects suggested that when the results of the two methods did not agree, the differences were due to an interaction between signal level and the unique input/output characteristics of the subjects' hearing aids. A precautionary measure is suggested for those who wish to use sound field aided threshold data to estimate the SLs at which children receive amplified conversational speech.

Adolescent↗
PubMed1992

Signal delivery/real ear measurement system for hearing aid selection and fitting.

This report describes a signal delivery/real ear measurement system for application in the hearing aid selection and fitting process. This signal delivery/real ear measurement system provides a means for quantifying a listener's auditory characteristics (e.g., thresholds, loudness discomfort levels) in a manner that is compatible with electroacoustic measures of hearing aid performance. The signal delivery/real ear measurement system consists of a button-type hearing aid receiver coupled to the listener's personal earmold, and a probe tube microphone system to measure the signal level within the occluded ear canal. This signal delivery/real ear measurement system was used to measure detection thresholds and loudness discomfort levels in severe/profoundly hearing-impaired school-age children, with results indicating good test-retest reliability in behavioral responses. The findings presented in this report relate to the intersession electroacoustic variability associated with this instrumentation. In addition, the potential application of this or a similar system for measuring real ear to 2-cc coupler difference values is illustrated and discussed.

Acoustic Impedance Tests↗
PubMed1991

Hearing loss in elderly patients in a family practice.

OBJECTIVE: To investigate hearing loss in elderly patients. DESIGN: Cohort study. SETTING: Family practice. PATIENTS: All ambulatory patients 65 years of age or older who attended the practice from June to August 1989. OUTCOME MEASURES: The Hearing Handicap Inventory for the Elderly--Screening Version (HHIE-S) and the Welch-Allyn Audioscope. Patients who failed one or both of the screening tests were referred to a speech and hearing clinic for audiologic assessment and treatment recommendations. Those with hearing aids were excluded from the main study but were given the opportunity to have them assessed at the clinic. MAIN RESULTS: Of 157 eligible patients 42 were excluded: 16 refused to participate, 13 already had hearing aids, and 13 could not be contacted. Of the remaining 115, 34 failed one or both of the tests (14 failed the HHIE-S, 9 failed the audioscope test, and 11 failed both). Of the 34, 25 completed the audiologic assessment at the clinic. Fifteen were found to have severe hearing impairment; the recommendation was hearing aids for 12, further assessment for 2 and no treatment for 1. Of the remaining 10 patients it was thought that 6 would benefit from hearing aids. Ten of the 11 patients with hearing aids who agreed to undergo testing at the clinic were found to need an adjustment or replacement of their devices. CONCLUSIONS: Hearing loss is a significant problem in elderly patients in primary practice. Further study is required to determine which of the two screening tools is most effective. Most elderly patients with hearing aids may require modification or replacement of their devices.

Aged↗
PubMed1991

Ear level recordings of the long-term average spectrum of speech.

The long-term average speech spectrum (LTASS) was measured at two different recording positions: 30 cm directly in front of the talker (reference position), and at the tragus of the talker's ear (ear-level position), for three groups of subjects: adult males, adult females, and children. Results indicated significant differences in the overall level and frequency spectra between the LTASS obtained at each microphone location. For all three groups of subjects the LTASS measured at the ear-level position consisted of more low frequency energy (i.e., below 1000 Hz) and less high frequency energy (i.e., above 2500 Hz) than did the LTASS measured at the reference microphone position. The findings suggest that the algorithms currently used to prescribe hearing aid gain may underestimate the sensation level of a hearing-impaired individual's own amplified speech productions at frequencies below 1000 Hz and overestimate the sensation level of a talker's own speech above 2500 Hz. The implications of these findings concerning selection of the electroacoustic characteristics of an amplification system for hearing-impaired individuals are discussed.

Adult↗
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↗
PubMed1985

Primary modality for speech perception in children with normal and impaired hearing.

The relationships between each of seven predictor variables and the relative degree to which 84 normal and hearing-impaired children used audition or vision in their perception of word stimuli were investigated. The children's relative use of audition or vision was assessed by the auditory-visual presentation of monosyllabic word stimuli in which the visual word stimuli were in conflict with those presented acoustically. Six of the seven predictor variables were significantly correlated with the performance scores obtained within the auditory-visual conflict condition. Only pure-tone average hearing level and auditory word identification performance, however, made unique contributions toward predicting the degree to which audition or vision was used in the perception of the word stimuli. We concluded that the relative use of audition or vision was almost completely related to their auditory capabilities as represented by the children's unaided threshold sensitivity and aided speech reception performance.

Adolescent↗
PubMedDate not supplied

Selecting amplification characteristics for young hearing-impaired children.

The task of selecting the electroacoustic characteristics of hearing aids for young hearing-impaired children continues to challenge many clinical audiologists. The rationale for a theoretically based approach to this problem is presented. Additionally, issues related to the choice of an idealized speech spectrum for a theoretical selection model are considered in relation to the acoustic environment and auditory needs of young hearing-impaired children. Finally, the preliminary version of a computer assisted speech spectrum approach, which facilitates the initial selection of frequency/gain and frequency/SSPL characteristics is presented.

Child, Preschool↗