Biomedical subjects

Michael Kiefte

Publications and source records attributed to Michael Kiefte.

6 recordsLinked to original sources

PubMed2006

The effect of SpeechEasy on stuttering frequency in laboratory conditions.

UNLABELLED: The effect of SpeechEasy on stuttering frequency during speech produced in a laboratory setting was examined. Thirteen adults who stutter participated. Stuttering frequencies in two baseline conditions were compared to stuttering frequencies with the device fitted according to the manufacturer's protocol. The fitting protocol includes instructions for deliberate use of vowel prolongation. Relative to the initial baseline condition, stuttering was reduced by 74%, 36%, and 49% for reading, monologue, and conversation, respectively. In comparison, stuttering was reduced by 42%, 30%, and 36%, respectively with the device in place, but before participants were instructed to deliberately prolong vowels. Examination of individual response profiles revealed that although stuttering reduced in the device compared to the baseline conditions during at least one of three speech tasks for most participants, degree and pattern of benefit varied greatly across participants. EDUCATIONAL OBJECTIVES: The reader will be able to: (1) discuss recent research in altered auditory feedback that led to the development of SpeechEasy, (2) analyze and describe issues related to evaluating the treatment benefits of fluency aids, and (3) summarize the range of outcomes that were observed with SpeechEasy in this study.

Adult↗

PubMed2005

The relative importance of spectral tilt in monophthongs and diphthongs.

Ito et al. [J. Acoust. Soc. Am. 110, 1141-1149 (2001)] demonstrated that listeners can reliably identify vowel stimuli on the basis of relative formant amplitude in the absence of, or in spite of, F2 peak frequency. In the present study, formant frequencies and global spectral tilt are manipulated independently in synthetic steady-state vowels. Listeners' identification of these sounds demonstrate strong perceptual effects for both local (formant frequency) and global (spectral tilt) acoustic characteristics. Subsequent experiments reveal that effects of spectral tilt are attenuated in synthetic stimuli for which formant center frequencies change continuously. When formant peaks are kinematic, perceptual salience of the relative amplitudes of low- and high-frequency formants (as determined by spectral tilt) is mitigated. Because naturally produced English vowels are rarely spectrally static, one may conclude that gross spectral properties may play only a limited role in perception of fluently produced vowel sounds.

Humans↗

PubMed2005

Pattern playback revisited: unvoiced stop consonant perception.

Among the most influential publications in speech perception is Liberman, Delattre, and Cooper's [Am. J. Phys. 65, 497-516 (1952)] report on the identification of synthetic, voiceless stops generated by the Pattern Playback. Their map of stop consonant identification shows a highly complex relationship between acoustics and perception. This complex mapping poses a challenge to many classes of relatively simple pattern recognition models which are unable to capture the original finding of Liberman et al. that identification of /k/ was bimodal for bursts preceding front vowels but otherwise unimodal. A replication of this experiment was conducted in an attempt to reproduce these identification patterns using a simulation of the Pattern Playback device. Examination of spectrographic data from stimuli generated by the Pattern Playback revealed additional spectral peaks that are consistent with harmonic distortion characteristic of tube amplifiers of that era. Only when harmonic distortion was introduced did bimodal /k/ responses in front-vowel context emerge. The acoustic consequence of this distortion is to add, e.g., a high-frequency peak to midfrequency bursts or a midfrequency peak to a low-frequency burst. This likely resulted in additional /k/ responses when the second peak approximated the second formant of front vowels. Although these results do not challenge the main observations made by Liberman et al. that perception of stop bursts is context dependent, they do show that the mapping from acoustics to perception is much less complex without these additional distortion products.

Acoustic Stimulation↗

PubMed2004

Optimum tension for partial ossicular replacement prosthesis reconstruction in the human middle ear.

OBJECTIVE: Hearing results from ossiculoplasty are unpredictable. There are many potentially modifiable parameters. One parameter that has not been adequately investigated in the past is the effect of tension on the mechanical functioning of the prosthesis. Our goal was to investigate this parameter further, with the hypothesis that the mechanical functioning of partial ossicular replacement prostheses (PORP) from the stapes head to the eardrum will be affected by the tension that they are placed under. METHODS: Fresh temporal bones were used to reconstruct a missing incus defect with a PORP-type prosthesis. Three different lengths of PORP were used, and the stapes vibrations were measured with a laser Doppler vibrometer using a calibrated standard sound in the ear canal. Eight temporal bones were used. RESULTS: Tension had a very significant effect on stapes vibration. In general, loose prostheses resulted in the best overall vibration transmission. The effects were most marked at the lower frequencies. There was a slight advantage to tight prostheses in the higher frequencies, but much less than the decrement in lower frequencies with tight prostheses. CONCLUSION: In ossicular reconstruction, best stapes vibration results in our model are achieved by shorter prostheses, which result in lower tension.

Cadaver↗

PubMed2004

Comparison of the mechanical performance of ossiculoplasty using a prosthetic malleus-to-stapes head with a tympanic membrane-to-stapes head assembly in a human cadaveric middle ear model.

HYPOTHESIS: Ossiculoplasty using prosthetic reconstruction with a malleus assembly to the stapes head will result in better transmission of vibrations from the eardrum to the stapes footplate than reconstruction with a tympanic membrane assembly to the stapes head. Both types of reconstruction will be affected by tension of the prosthesis. BACKGROUND: Theories (and some clinical studies) that the shape of the normal tympanic membrane is important suggest that prosthetic reconstruction to the malleus performs better than reconstruction to the tympanic membrane. This has not been previously tested by directly measuring vibration responses in the human ear. Our previous work suggests that tympanic membrane assembly to the stapes head type prostheses performed best under low tension. This had not been previously tested for malleus assembly to the stapes head type prostheses. METHODS: Hydroxyapatite prostheses were used to reconstruct a missing incus defect in a fresh cadaveric human ear model. Two types of prostheses were used, one from the stapes head to the malleus (malleus assembly to the stapes head), the other from the stapes head to the tympanic membrane (tympanic membrane assembly to the stapes head). Stapes footplate center responses were measured using a laser Doppler vibrometer in response to calibrated acoustic frequency sweeps. RESULTS: Tension had a very significant effect on both types of prostheses in the lower frequencies. Loose tension was best overall. The malleus assembly to the stapes head type prostheses consistently performed better than the tympanic membrane assembly to the stapes head type prostheses when stratified for tension. CONCLUSION: Tension has a significant effect on prosthesis function. Malleus assembly to the stapes head type prostheses generally result in better transmission of vibrations to the stapes footplate than tympanic membrane assembly to the stapes head type prostheses.

Biomechanical Phenomena↗

PubMed2002

Responses to cochlear normalized speech stimuli in the auditory nerve of cat.

Previous studies of auditory-nerve fiber (ANF) representation of vowels in cats and rodents (chinchillas and guinea pigs) have shown that, at amplitudes typical for conversational speech (60-70 dB), neuronal firing rate as a function of characteristic frequency alone provides a poor representation of spectral prominences (e.g., formants) of speech sounds. However, ANF rate representations may not be as inadequate as they appear. Here, it is investigated whether some of this apparent inadequacy owes to the mismatch between animal and human cochlear characteristics. For all animal models tested in earlier studies, the basilar membrane is shorter and encompasses a broader range of frequencies than that of humans. In this study, a customized speech synthesizer was used to create a rendition of the vowel [E] with formant spacing and bandwidths that fit the cat cochlea in proportion to the human cochlea. In these vowels, the spectral envelope is matched to cochlear distance rather than to frequency. Recordings of responses to this cochlear normalized [E] in auditory-nerve fibers of cats demonstrate that rate-based encoding of vowel sounds is capable of distinguishing spectral prominences even at 70-80-dB SPL. When cochlear dimensions are taken into account, rate encoding in ANF appears more informative than was previously believed.

Acoustics↗