Biomedical subjects

C A Kamm

Publications and source records attributed to C A Kamm.

6 recordsLinked to original sources

PubMed1985

Speech recognition and the Articulation Index for normal and hearing-impaired listeners.

The purpose of this experiment was to determine the applicability of the Articulation Index (AI) model for characterizing the speech recognition performance of listeners with mild-to-moderate hearing loss. Performance-intensity functions were obtained from five normal-hearing listeners and 11 hearing-impaired listeners using a closed-set nonsense syllable test for two frequency responses (uniform and high-frequency emphasis). For each listener, the fitting constant Q of the nonlinear transfer function relating AI and speech recognition was estimated. Results indicated that the function mapping AI onto performance was approximately the same for normal and hearing-impaired listeners with mild-to-moderate hearing loss and high speech recognition scores. For a hearing-impaired listener with poor speech recognition ability, the AI procedure was a poor predictor of performance. The AI procedure as presently used is inadequate for predicting performance of individuals with reduced speech recognition ability and should be used conservatively in applications predicting optimal or acceptable frequency response characteristics for hearing-aid amplification systems.

Adult↗

PubMed1983

Accuracy of adaptive procedure estimates of PF-max level.

A measure of maximum speech recognition ability (PB max) is often obtained in the clinical audiologic evaluation of patients. However, without developing a complete performance-intensity function (PIF), it is often difficult to determine an appropriate intensity level for measuring PB max. Levitt (1978) has described an adaptive procedure designed to estimate an intensity level at which maximum speech recognition performance could be measured. We have investigated the accuracy of this procedure by comparing speech recognition performance on a CNC word list presented at the level estimated by the adaptive procedure with maximum performance as measured on the listener's performance-intensity function. Using the presentation level indicated by the adaptive procedure, PB max scores were obtained for 12 of 16 normally hearing subjects and 19 of 25 listeners with mild-to-moderate sensorineural hearing loss. Similar accuracy was obtained for the hearing-impaired subjects using a single presentation level of 95 dB SPL, while use of a 40 dB SL speech level would have resulted in a lower proportion of PB-max measurements. Although PB max is most accurately estimated by delineating the entire performance-intensity function, the current results suggest that, if speech recognition is to be measured only at a single level, scores obtained at the level estimated by the adaptive procedure or at 95 dB SPL may serve as reasonable estimates of PB max for listeners with primarily cochlear hearing losses of less than or equal to 50 dB.

Adolescent↗

PubMed1982

Some effects of spectral shaping on recognition of speech by hearing-impaired listeners.

The effects of spectral shaping on speech recognition were investigated for hearing-impaired listeners with flat and steep audiometric configuration. Three frequency responses were tested: uniform frequency gain, high pass filtering, and a response shaped relative to each subject's loudness discomfort level curve. Speech-recognition performance was measured at four levels (from 80 to 95 dB SPL) using nonsense syllable (NST) and synthetic sentence (SSI) tests, presented against a background of "cafeteria noise." No significant differences in performance on the NST were observed between the two subject groups across all spectral shapes (frequency response) and presentation levels. On the SSI, performance of subjects with flat audiometric configuration was highest using the uniform frequency response, while performance of listeners with steep configuration was poorest for the uniform response. The recognition data were compared with predictions of relative performance using a modification of the Articulation index (AI). The AIs provided accurate estimates of relative performance across spectral shapes but were not consistent with relative performance as a function of presentation level. The results indicate that the selection of spectral shape for optimal performance is influenced by the particular speech task used to test recognition and also suggest that, with further validation, the AI may provide an objective technique for selecting optimal spectral shape.

Aged↗

PubMed1981

Form equivalence of the speech perception in noise (SPIN) test.

An evaluation was conducted of the equivalence of the ten forms of the Speech Perception in Noise (SPIN) Test with normal hearing subjects. Each subject was tested monaurally on all ten forms. Twenty-five subjects were presented the materials at 80 dB SPL at a signal-to-babble ratio of - 1 dB. An additional 25 subjects heard the materials at 30 dB SPL, at a signal-to-babble ratio of + 3 dB. The data were analyzed for equivalence using a parallel tests model. A detailed rationale for the application of this model to the equivalence of the SPIN test is presented. The results indicated that a subset of seven lists fits the equivalence model for PH, PL, and difference (PH - PL) scores. Additionally, analysis of list-pair data (combination of companion forms) suggested that all five list-pairs resulted in equivalent performance.

Adult↗

PubMed1981

Speech recognition performance at loudness discomfort level.

The purpose of this experiment was to determine the relationship between the loudness discomfort level (LDL) and maximum speech recognition performance for listeners with sensorineural hearing loss. Performance-intensity functions were obtained for 30 listeners with mild to moderate sensorineural hearing impairment at five speech levels from -18 to +4 dB re: the LDL. Recognition scores were obtained for three speech materials. For all speech materials, recognition scores at levels below the LDL were equivalent to or higher than scores obtained at and above the LDL. These results support the contention that the LDL represents a sound pressure level above which no improvement in speech recognition occurs, and thus, might reasonably be used as the appropriate level for the saturation sound pressure level of a hearing aid.

Amplifiers, Electronic↗

PubMed1979

Loudness discomfort level and acoustic reflex threshold for speech stimuli.

Loudness discomfort level (LDL) and acoustic reflex threshold (ART) measurements were obtained from subjects with normal hearing using several speech stimuli, as well as broad-band and speech-spectrum noise. The purpose of the investigation was to determine the LDL for a variety of representative speech samples, and to determine the relationship between the LDL and ART for selected speech and noise stimuli. For all stimuli, LDL measurements were relatively constant, but ART measurements decreased significantly for wide-band noise stimuli as compared with the speech stimuli. Mean differences between the two measures were consistent, but individual subject data were characterized by wide variability precluding accurate prediction of the LDL from ART measurements.

Acoustic Stimulation↗