In this paper, several speech sounds are examined by masking methods to show typical examples of speech spectrum representation in the auditory pathway represented by a spatio-temporal masking pattern and to clarify differences between internal and physical representation of speech spectrum. Three types of Japanese speech, monosyllables, a sentence utterance and a time-reversed monosyllable, are chosen for masker sounds. Using 1/3 octave band noise bursts of 25ms duration as probe signals, simultaneous and temporal masking values are measured for the whole period of each masker. The spatio-temporal masking pattern thus obtained is an internal speech spectrum. Com-pared with the physical spectral pattern, speech onsets and the formant structure, parti-cularly the formant transition, are enhanced and prominently represented in the masking patterns. These spectral enhancements in the auditory pathway are assumed to be the result of three auditory peripheral functions, AM/FM masking, forward/backwardmasking and adaptation. Further, taking into account the considerable differences between the internal and the physical representation of speech spectrum, the importance of the internal speech spectrum representation in the field of speech science is discussed.

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Tonotopic organization and, in particular, the isofrequency planes in the brainstem audi-tory nuclei of the rat were studied by the ¹⁴C-2-deoxyglucose (2DG) method. With wideband noise stimulation, 2DG labeling was seen diffusely in the brainstem auditory nuclei, but with pure or complex tone stimulation, labeling of narrow 2DG-uptake bands were seen in the cochlear nucleus and inferior colliculus, each band corresponding to the frequency component of the stimuli. In the superior olivary complex, the nuclei of the lateral lemniscus, and the medial geniculate body, labeling with the pure tones was not so selective as that in the cochlear nucleus and inferior colliculus. The iso-frequency contours in the cochlear nucleus and inferior colliculus were studied in serialfrontal and sagittal sections of the brain and three-dimensional structures of the iso-frequency planes in these nuclei were analyzed.

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Design charts of a sound absorbing wedge made of glass wool are proposed. They arecalculated using a computer simulation model developed for porous sound absorbing materials, such as glass wool. The model is confirmed experimentally using a precise measurement method of complex sound reflection coefficients of acoustic materials. Using the design charts an optimum wedge structure can be easily designed by specifying wedge parameters, that is, cutoff frequency, base width of the wedge and airflow resistivity of glass wool. Relation between airflow resistivity and volume density of a glass wool material which is conformed to Japanese Industrial Standard is also investi gatedfor designing a wedge using density instead of airflow resistivity.

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The sound radiation characteristics of actually rolling tires with three types of the tread patterns were measured by the 2-microphone sound intensity technique. The measure mentswere performed at a test course in Japan Automobile Research Institute, in which a special trailer equipped with an automatic microphone scanning system was used and the normal sound intensity distribution in a plane parallel to the sidewall of a tire was measured during actual running. The results show that it is possible to identify the source positions on a tire actually rolling on a road surface by means of the soundin tensity technique. In the case of a rib tire, the noise was mainly generated from the leading and the trailing edges, not from the contact patch, while in the case of a lug tire, the main source position was the contact patch. The noise radiation pattern varied according to the difference of tread pattern. Further, the sound power radiated by three kinds of tires were compared. A-weighted sound power level of the lug tire is the biggest among them.

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