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May 1984

Volume 75, Issue S1, pp. S1-S93

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back to top Session P. Physiological Acoustics VI and Psychological Acoustics IV: Tinnitus, Audiometry, and Aids for the Deaf
Contributed Papers
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Electrical tinnitus control (A)

Abraham Shulman and Juergen Tonndorf

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S31-S31 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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Tinnitus can be suppressed electrically in various ways: Grapengiesser (1801), Wreden (1887), Aran (1981), and Chouard (1981). The present portable instrument uses a new technique: audio frequencies that vary continuously but slowly between 0.2 and 20 kHz modulate a 60‐kHz carrier. The combined signal (1.77 V rms, 5–6 mA) is applied to stainless‐steel electrodes placed on both mastoids. Exposure starts with 1 h/day, increasing up to 5 h/day. It may be reduced again, once supression is achieved. This mode of control is currently tested on a number of patients, who complain of severe tinnitus. If results continue to be favorable (50%–60% success), this method appears to be superior to acoustic masking because (1) patients have no sensations during exposure, the signals being much below auditory or tactile thresholds, (2) simultaneous auditory inputs are neither masked nor attenuated, (3) the ear canals remain free, without irritation, and (4) “residual inhibition” (continued suppression after cessation of stimulation) lasts for several hours or even days, instead of minutes or a few hours, although suppression is not immediate, taking 2–5 h to take effect.
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Tinnitus occurence and modification—A case study (A)

Angelo J. Campanella

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S31-S32 (1984); (2 pages)

Online Publication Date: 12 Aug 2005

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In July 1982, a brief exposure to 133‐dB 400‐Hz sounds to the author caused a mild case of tinnitus to erupt that evening. Ancillary circumstances included insufficient earplug attenuation, fatigue, and hot weather. No significant TTS was noted at the time of exposure, though the environmental noise was sufficient to mask mild TTS. Tinnitus tones were generally above 4 kHz and occasionally of narrowband (versus tonal) quality at an SPL estimated to be about 35 dBA. Audiograms taken a few days after the exposure indicated no notable PTS, though personal experience indicated a slight loss of response in the 4‐, 5‐, or 6‐kHz region. Lack of sleep was relieved by medication and tinnitus masking for a few weeks. Long‐term acclimatization is now more or less complete. Recent measurements indicate that permanent tinnitus tones lie in the 10 to 13 kHz region. Mild exposure to noise (vis, a 60‐mile automobile trip without earplugs) incites lower tones in the 5‐ to 8‐kHz region which persist for a few hours. Mechanical pressure on certain skull locations will increase the 10/13‐kHz tinnitus tone level by 10 to 20 dB. Still another pressure point will stop the tone as long as the pressure is applied. Blood pressure pulses individually modulate the 10/13‐kHz tinnitus by an estimated 10 dB. Acoustical measurements pertinent to these observations will be presented. Such observations suggest that tinnitus can be altered by such mechanisms as pressure, stresses, or dislocations in the cochlear region. It is also possible that the damage mechanism (in this case) would include mechanical stress induced in the cochlear assembly and its attachments by intense sound vibrations.
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High‐frequency audiometry (A)

Juergen Tonndorf and Barbara Kurman

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S32-S32 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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High‐frequency hearing was routinely, although not very precisely, tested with the monochord, but this was no longer done after the advent of electronic audiometers. For many disorders, high‐frequency losses were recently shown to precede losses in the speech frequencies. At f> 6–8 kHz, precalibrated earphones become increasingly unreliable. Replacing the air conduction input by bone conduction, generated by electrical inputs (fixed carrier signal of 60 kHz, modulated by audio signals) overcomes these difficulties. Electrodes, placed on the mastoid and on the forearm, are Mylar‐coated to provide capacitive coupling, the subject becoming part of a tuned circuit. The nontest ear was being masked. Input voltage was kept constant at 1.77 V rms, since signal magnitude is mainly determined by current. For normal‐hearing subjects, thresholds varied with frequency between 1 and 25 mA. The current required rose with about 130 dB/oct near the upper frequency limit, which for young adults was found at about 18 kHz, with testing limited at 30 mA for safety reasons. However, some subjects with upper limits as low as 11 kHz still showed “normal” air‐conduction thresholds at 8 kHz.
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Detection of frequency modulation by normally hearing and severely‐to‐profoundly hearing‐impaired listeners (A)

Ken W. Grant

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S32-S32 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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Listeners with a severe to profound hearing loss often perceive changes in loudness when the frequency of a stimulus is changed. As a result, researchers who have studied frequency discrimination in impaired listeners may have underestimated the extent of the frequency impairment. In this study, we compare normal and impaired listeners in three frequency modulation detection experiments, in which the amplitudes of the test signals were either fixed, sinusoidally modulated at a constant rate of 3 Hz, or randomly modulated at rates of 3 Hz and below. Results for listeners with normal hearing showed that modulation of signal amplitude yielded Δ FMs that were 2–3 times larger than those obtained with fixed amplitude. Results for one impaired listener tested thus far show abnormally large Δ FMs for all conditions, and, in addition, that Δ FMs obtained with random amplitude modulation are as much as 45 times larger than those found for listeners with normal hearing. [Work supported by NIH.]
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Loudness discomfort level measurements and their implications for the design and fitting of hearing aids (A)

Harvey Dillon, Robyn Chew, Margaret Deans, and William Tonisson

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S32-S32 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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If the maximum power output (MPO) of a hearing aid is set at too high a level, then the aid wearer experiences discomfort from the intense sounds produced. This paper presents measurements of the loudness discomfort level (LDL) of 120 hearing‐impaired individuals. As well as large differences between the average LDLs of the subjects, there are large differnces in the shapes of the LDL curves. For subjects with severe to profound losses, the shape of the LDL curve is closely related to the shape of the threshold curve. Some of these individuals have as little as 5‐dB dynamic range available between their threshold and LDL at some frequencies. The extreme range of shapes, especially when combined with narrow dynamic ranges implies that a similar range of shapes should be available in the MPO curves of hearing aids if aid wearers are to have an audible, comfortable signal present in each frequency region. This feature can be readily arranged in aids incorporating compression limiting.
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Improved frequency‐lowering technique (A)

M. P. Posen, C. M. Reed, L. D. Braida, and N. I. Durlach

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S32-S32 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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Frequency lowering is a form of signal processing intended to make high‐frequency speech cues available to those who cannot hear high‐frequency sounds. We have evaluated a frequency‐lowering technique studied by Lippmann [J. Acoust. Soc. Am. Suppl. 1 67, S78 (1980)]. In this system speech levels in high‐frequency bands modulate 1/3 octave bands of noise at low frequencies, which are then added to unprocessed speech. We found, in agreement with Lippmann, that processing improved the recognition of stop and fricative consonants when the listening bandwidth is restricted to 800 Hz. However, we also found that processing degrades the perception of nasals and (particularly) semivowels, consonants not included in Lippmann's study. We modified Lippmann's signal processing by reducing the level of the modulated noise when low‐frequency components dominate the speech signal. Preliminary results indicate that the modified system does not degrade nasals and semivowels, but maintains the processing advantage for stops and fricatives. [Work supported by NIH.]
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Hearing aid signal processing for noise and nonsense syllables (A)

David A. Preves

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S32-S32 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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Transfer function magnitude and phase, coherence, cross power spectrum, and cross correlation measurements for vented hearing aid fittings worn in situ near onset of acoustic feedback oscillation were obtained with linear system identification techniques utilizing a FFT spectrum analyzer. These measurements were repeated for various methods of suppressing the oscillation tendency. Time segments containing formant transitions of selected CV and VC nonsense syllables found to be difficult to perceive by hearing‐impaired persons were passed through the vented hearing aid fittings worn in situ. The ability of the hearing aids to process difficult‐to‐perceive speech stimuli is discussed in light of interpreting the cross correlation and cross spectrum measurements.
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Visual speech display for the deaf (A)

Stephen A. Zahorian and James R. Holland

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S32-S32 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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In this paper, the results of the preliminary development of a visual speech display as a speech training aid for the hearing impaired will be presented. The training aid consists of analog electronics for extracting speech parameters and a microprocessor‐based system for converting the speech parameters to color parameters and for controlling the display parameters. The speech parameters consist of six spectral shape factors, similar to speech spectral principal components and a pitch signal proportional to voice fundamental frequency. The spectral shape factors are computed by appropriately combining the low‐pass‐filtered logarithmically scaled outputs of a bank of 16 bandpass filters. The spectral shape factors will be used to control the color of the display, and the pitch signal will be used to control “texture” in the display. The results of a vowel discrimination experiment for steady‐state vowels will be presented. [Work supported by the Whitaker Foundation.]
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The evaluation of speech‐to‐tactile transformations utilizing two training paradigms (A)

Matt Fluster

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S32-S33 (1984); (2 pages)

Online Publication Date: 12 Aug 2005

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Two distinct training paradigms, building block and holistic, were used to evaluate two speech‐to‐tactile transformations, vocoder and flowed spectrographic. A separate group of subjects was used for each of the four conditions in the 2 × 2 (transformation × training) experimental design. The building block subjects were taught first to identify a small set of vowels and consonants, followed by CVs and VCs, nonsense words, small phrases, and finally, small phrases in conjunction with a simple, visually presented game. Each level used elements from the preceding level. With the holistic paradigm, the subjects were only presented with the final task. No significant difference in the overall effectiveness of the vocoder versus the flowed spectrographic transformation was seen. However, in the initial level of the building block paradigm, vocoder subjects relied more heavily on durational cues. The stimuli were constructed following simple phonological, syntactic, and semantic rules. This stimulus structure was seen to have specific effects on the types of confusions found with the building block paradigm, and on the manner in which the subjects learned the tactile patterns in the holistic paradigm. Results of these experiments have implications for the evaluation of communication aids. [Work supported by NSF and NIH training Grant 5T32GM07057.]
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Categorical perception of vibrotactile signals (A)

M. J. Collins and R. R. Hurtig

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S33-S33 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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Hearing‐impaired children's successful use of vibrotactile devices as a substitute for audition may be dependent on the wearability of the device and the transmission of phonemically recognizable information. The present study was carried out to determine the extent to which categorical perception of voiced‐voiceless cognates could be achieved with a commercially available, wearable, single‐channel, vibrotactile device. Stimuli were computer‐generated pairs of syllables differing only in voice onset time (ka‐ga). Adult subjects with normal hearing were trained to identify tactile signals at the extreme of the continuum prior to collection of discrimination data. Peaks in discrimination functions were observed to mark voiced‐voiceless boundaries for both acoustic and tactile stimulation modes. These peaks occurred at consistently longer voice onset times for tactile stimulation than for auditory stimulation. The results indicate that although categorical perception of speech sounds can be learned in the tactile mode, because of the shift in the boundary, voiced‐voiceless confusions may occur with voice onset times commonly observed in real speech. Thus for effective use of the tactile modality for speech, specialized signal processing may be required.
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Consequences of audiovisual asynchrony for speech perception: Implications for signal processing in aids to lipreading (A)

Matthew McGrath and Quentin Summerfield

J. Acoust. Soc. Am. Volume 75, Issue S1, pp. S33-S33 (1984); (1 page)

Online Publication Date: 12 Aug 2005

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Audiovisual identification of sentences was measured as a function of audio delay in untrained listeners with normal hearing; the sound track was replaced by rectangular pulses originally synchronized to the closing of the talker's vocal folds and then subjected to delay. Although group‐mean performance declined monotonically with delay, systematic decrements occurred only when delay exceeded 80 ms. A similar tolerance of delay was found in judgments of audiovisual onset time when observers determined whether a 120‐Hz triangular wave started before or after the opening of a pair of liplike Lissajou figures. Group‐mean 70% DLs were − 78 ms (sound leading) and + 137 ms (sound lagging). This result suggests, first, that most observers possess insufficient sensitivity to intermodal timing cues in audiovisual speech for them to be used analogously to VOT in auditory speech perception, and, second, that the effects found in the first experiment derive from syllabic rather than phonemic interference. However, the best lipreaders, who also gained most from the audio signal in that experiment, were affected by delays shorter than 80 ms. Accordingly, we suggest that signal processing in aids to lipreading should be allowed no more than 40 ms to do its work. Supported by a studentship from the TWJ Foundation.
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