Otoacoustic emissions are sounds produced by the inner ear. In humans, and other mammal species, all normal ears produce otoacoustic emissions in response to sound stimuli. Within the inner ear, a mechanism called the cochlear amplifier utilizes metabolic energy to enhance the sound-induced vibration of the basilar membrane. The enhanced basilar-membrane vibration forms the basis of normal hearing sensitivity. The operation of the cochlear amplifier is impaired by a variety of traumas, resulting in reduced basilar-membrane vibration and, thus, hearing loss. Impaired operation of the cochlear amplifier is associated with reduced or abolished otoacoustic emissions. Otoacoustic emissions and the action of the cochlear amplifier are both characterized by sharp frequency tuning and a high degree of nonlinearity. Thus, otoacoustic-emission generation is intimately related to the normal function of the cochlea, and appears to reflect the action of the cochlear amplifier. Otoacoustic emissions are in widespread use for the assessment of cochlear function in basic-science studies, and in clinical applications. Nevertheless, the cochlear processes underlying the enhancement of basilarmembrane motion and the generation of otoacoustic emissions are not well understood.

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In response to recent demand for greater miniaturization of underwater sound pro-jectors, the authors have applied both finite element method (FEM) analysis and equiv-alent circuit analysis to the design of a disk bender projector with dual radiation surface which utilizes two piezoelectric ceramic disks operating in an unstiffened mode. The projector fabricated from this design is miniature and light-weight (200 mm in diameter, 32 mm thick, and 4.27 kg in weight). The resonant frequencies of the projector in air and water are, respectively, 1315 Hz and 970 Hz, and experimental maximum trans-mitting voltage sensitivity is 132.2 dB re 1 μPa/V at 1 meter. The sound pressure level is 192.0 dB re 1 μPa at 1 meter when an input voltage of 143.7 V_rms/mm is applied to the piezoelectric ceramic disks.

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The peak intensity values of vowels in several CV moras were studied, using a passage of news-broadcasting read by a professional male speaker. Several factors operate in determining vowel intensity.(1) Grammatical function of the word in which the vowel is located: the most significant and consistent difference is higher intensities for nouns than verbs; however, vowels in reduced nouns with more functional roles (such as /ka/in “no-naka-de” ‹in the›) show verb-like intensities.(2) Phrasal or sentential position of the mora: the vowel intensity is higher at the beginning and lower near the end.(3) Position within the word and word length: vowels in the first three moras of a noun are relatively high in intensity, while those near the end of a long compound noun (12th and later) are extremely low.(4) Vowels in particles and verb inflections are high in intensity when there is a strong continuation to the following word or phrase.(5) Accent patterns generally do not play a significant role; however, certain articulatory sequences produce a dramatic intensity difference between accented and non-accented vowels in the first mora of a word.

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This paper describes the Subband-Autocorrelation (SBCOR) analysis technique and investigates how to apply it to speech recognition. The SBCOR analysis is a new signal analysis technique based on filter bank and autocorrelation analysis. The SBCOR analysis system is evaluated for five types of filter bank and three autocorrelation detectors using a speaker-dependent DTW word recognition system. The experimental results show that the SBCOR spectrum performs equally as well as the smoothed group delay spectrum under clean conditions, and much better than it under noisy conditions. Finally, it is shown that the most suitable filter bank is a fixed Q filter bank whose center frequencies are equally spaced on the Bark scale, and the most suitable autocorrelation analysis is a conventional autocorrelation detection without controlling weak signals. An analysis example of speech is also shown under these conditions.

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A new method is described for non-contact measurement of particle velocity distribu-tion along an elastic bar excited by a PZT transducer. By analyzing two signals measur-ed by a laser Doppler velocimetry (LDV) from two incident angles, the particle velocity distribution for each of the two components, normal and parallel to the bar axis, is separately obtained. The principle of the proposed measurement method is confirmed by the experiments using a Langevin type PZT transducer having a resonant frequency of 17 kHz. The sensitivity of this method is enough high to measure the particle velocity less than 12 μm/s at the resonant frequency of 17 kHz.

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An intensity effect has been found on auditory duration discrimination using a short target tone between long preceding and succeeding flanking tones. The measured discrimination thresholds significantly increased with decreasing target levels; the largest discrimination threshold was obtained in the silence condition where the target portion was an empty interval. Such a systematic intensity effect could not be observed in the control condition where the target was presented with no flanking sound.

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