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Biomedical subjects

J P Preece

Publications and source records attributed to J P Preece.

8 recordsLinked to original sources
PubMed1992

Natural vowel perception by patients with the ineraid cochlear implant.

Vowel recognition was tested in 10 patients using the Ineraid cochlear implant. The vowels were produced by a male speaker in the context 'heed, hid, head, had, hawed, hood, who'd, hud' and 'heard'. Performance varied from 34 to 93% correct. A descriptive feature system for the vowels was determined from an acoustic analysis. An information transfer analysis of these features suggested that information about the first formant frequency, vowel duration and fundamental frequency was transmitted. Information about the second and third formant frequency was transmitted less well. A sequential information transmission analysis suggested that the features of the first formant and duration accounted for nearly 80% of the information transmitted. The fundamental frequency and second formant frequency information accounted for an additional 8%. Information provided by the third formant frequency was largely redundant.

Adult↗
PubMed1992

Relationship of pure-tone averages to speech reception threshold for male and female speakers.

The availability of a compact disc with a female speaker for clinical use has raised the issue of the equivalence between the female speaker and the previous standard male speaker for assessing the speech reception threshold (SRT). This study evaluated the relationship of two- and three-frequency averages to the SRT for a male speaker on an audio tape and a female speaker on a compact disc in two similar groups of clinic patients, each consisting of 215 ears. There were no significant differences between the SRTs for the two groups, suggesting that the two speakers/recordings are equivalent for clinical purposes. The SRTs from both speakers/recordings were within 6 dB of both the two- and three-frequency averages. There were no significant differences between the SRTs and the three-frequency average.

Acoustic Stimulation↗
PubMed1991

Enhancement of word-recognition performance with a filtering technique.

The NU No. 6 materials spoken by a female speaker were passed through a notch filter centered at 247 Hz with a 34-dB depth. The filtering reduced the amplitude range within the spectrum of the materials by 10 dB that was reflected as a 7.5-vu reduction measured on a true vu meter. Thus, the notch filtering in effect changed the level calibration of the materials. Psychometric functions of the NU No. 6 materials filtered and unfiltered in 60-dB SPL broadband noise were obtained from 12 listeners with normal hearing. Although the slopes of the functions for the two conditions were the same, the functions were displaced by an average of 5.8 dB with the function for the filtered materials located at the lower sound-pressure levels.

Analog-Digital Conversion↗
PubMed1989

Temporal-gap detection by cochlear prosthesis users.

Minimum-detectable gaps for sinusoidal stimuli were measured for three users of a multi electrode cochlear prosthesis as functions of stimulus level, frequency, and electrode place within the cochlea. Stimulus level was scaled by sensation level and by growth-of-loudness functions generated for each condition by direct magnitude estimation. Minimum-detectable gaps decreased with increase in either sensation level or loudness, up to a plateau. When compared at equal sensation levels, the minimum-detectable gaps decreased with frequency increases. The frequency effect on minimum-detectable gaps is reduced if the data are considered at equal loudness. Comparison across place of stimulation within the cochlea showed minimum-detectable gaps to be shorter for more basal electrode placement at low stimulus levels. No differences in minimum-detectable gap as a function of place were found at higher stimulus levels.

Adult↗
PubMed1988

Detection, loudness, and discrimination of five-component tonal complexes differing in crest factor.

The detection, loudness, and discrimination performances of subjects with normal hearing were assessed using 3 five-component tonal complexes (1020-1100 Hz) with crest factors of 1.8, 2.6, and 3.2. The 3 five-component tonal complexes were: (1) equally detectable in broadband noise when presented at equal rms amplitude; (2) perceived as equally loud when presented at essentially equal rms amplitude; and (3) discriminable from one another when presented at equal loudness. The present data indicate that listeners can make discriminations on the basis of amplitude variations.

Acoustic Stimulation↗
PubMed1986

Previous experience as a confounding factor in comparing cochlear-implant processing schemes.

It is of great importance to compare the relative merits of different cochlear-implant speech-processing strategies. Some groups have compared different strategies within single subjects, but usually the subject has prior experience with one strategy, and no allowance is made for this prior experience. We show in the present study that this is inappropriate. We tested one subject using the Melbourne (Cochlear Corp.) multichannel implant with the device set to process sounds in two different ways. In the first processing scheme, the device functioned normally, extracting information about voicing frequency, amplitude and second-formant frequency. This information activated the 21-channel device, determining pulse rate, pulse amplitude and electrode position (respectively). In the second processing scheme, a single electrode (with the largest dynamic range) was activated. This electrode coded overall amplitude and voicing frequency. The subject was tested on an audiovisual test of a 14-choice consonant recognition in the form /iCi/ over a period of over 4 months. During this time the subject used the 21-channel processor outside of the laboratory. Upon initial connection, there was little difference between the results obtained with the two schemes when tested in sound alone or in sound plus vision. However, after about 4 months, scores obtained with the 21-channel processor in sound plus vision were superior to the scores obtained with the one channel. This advantage came from a superiority in the features of voicing and nasality, but not place. Scores for sound-alone conditions between the two processing schemes remained similar for the 4-month period.(ABSTRACT TRUNCATED AT 250 WORDS)

Auditory Threshold↗
PubMedDate not supplied

Audiological results with two single channel cochlear implants.

We tested six patients with single channel cochlear implants on several tests from the Minimal Auditory Capabilities battery and the Iowa Cochlear Implant Tests. All patients were able to discriminate some everyday sounds and to identify the number of syllables in the words presented. Five patients were able to identify speaker sex reliably. Surprisingly, some patients had difficulty discriminating between a modulated noise and a voice or between a question and a statement or identifying the accented word in a sentence. On several audiovisual tests, an improvement was observed for the sound plus vision condition compared to the vision only condition. This was particularly true for sentence tests, but was not uniform across patients or across tests.

Adult↗