Curved rigid boundaries are often used in an auditorium, composing a part of the early reflections and it is therefore very important to know their sound reflections. If a curved rigid panel is replaced by tangential plane partitions, the diffracted formula under Kirchhoff's boundary conditions is applicable to them in order to calculate the first reflection of the panel. When the interreflection on the surface is neglected and a panel is divided into partitions to be able to apply Fraunhofer's diffraction formula, the sound reflection of a curved rigid panel is approximated by the sum of their first reflections. Transfer function and impulse response of the panel are thus calculated. Calculated values for a few kinds of curved rigid panels are compared with measured values. They show good agreement. When the curvature of a panel is changed, the sound reflection is compared by calculation. The sound reflection of an actual curved rigid lateral wall is estimated by this method and compared with the measurement. They also agree well. For the periodically curved panel, it is shown that this approximation of calculation gives useful information.

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In order to make clear the characteristics of elliptic cylindrical chambers of a muffler, the distribution of sound pressure is calculated by solving the wave equations, assuming that the loss can be neglected. In addition, the effective frequency range is defined by theoretical investigation and verified by experiment on the formation of higher modes and on the position of input and output pipes.

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Based on theoretical and computational analyses, a striking symmetry property of the ultrasonic light diffraction spectrum with respect to the angle of incidence is obtaincd. This is to be stated as the following correspondence rule:(a) The intensity of the Braggside qth-order spectrum under (q+s) th-order Bragg incidence is the same with the intensity of the Bragg-side qth-order spectrum nunder (q-s) th-order Bragg incidence (q, s=1, 2, 3, …; q>s).(b) In case q=s, the correspondence rulebecomes as follows: The Bragg-side qth-order spectrum under 2qth-order Bragg incidence is of the same intensity with the ± qth-order spectra under normal incidence.(c) If q-s<0, the rule becomes as: The Bragg-side qth-order spectrum under (s+q) th-order Bragg incidence is of the same intensity with the anti-Bragg side qth-order spectrum under (s-q) th-order Bragg incidence. This rule holdstrue irrespective of the values of the parameters pertaining to this phenomenon. The correspondence rule is equivalent to the following reciprocity theorem: The intensity of the ultrasonic light diffraction spectrum remains the same when the light is incident in the reversed direction of the diffraction spectrum and the spectrum produced in the inverted direction of the initial incident light is observed.

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A closed form formula with by far the better accuracy than the Raman-Nath formula is proposed. The new formula is also applicable under oblique incidence, explaining the asymmetry of the diffraction spectrum. The formula is a semi-empirical modifica-tion of the Raman-Nath formula taking into account the requirement of the symmetry property around the Bragg incidence angle-the correspondence rule-of the ultrasonic light diffraction spectrum. The formula contains, besides the usual phase-lattice param-eter υ(=2πδη·Lλ_vac), a second parameter D (=πLλ/Λ²), also in case of the normal incidence. Here λ and λ_vac are the wavelength of light in the medium and in vacuum, respectively, Λ is the ultrasonic wavelength, L the beamwidth of the ultrasound, and δn the amplitude of variation of the reffactive index of the medium perturbed by ultrasound.

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For the measurement of sound power level of vehicle noise in constant speed run, a new method using a reverberant tunnel is investigated. This measuring method is a kind of sound source substitution method in a reverberant sound field, which makes the measurement easier and more accurate, compared with the ordinary method. By making a field measurement on road vehicles in actual use using this new method, 179 data of passenger cars and 490 data of heavy vehicles were obtained. Concerning these results, the correlations between A-weighted sound power level and such vehicle properties as running speed, total weight, and type of tires are investigated.

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“Q -Codes, ” a system of manual signs proposed by G. Fant as an aid for Swedish lipreading is discussed in terms of its adaptability to Japanese, based on the rules of Japanese lipreading.

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Auditory cortex neurons responded with “on” and/or “off” responses to pure tone stimuli and did not exhibit sustained responses in the cats anesthetized with barbiturate. But in human audition, sensation to a continuous tone is sustained. Therefore, it is expected that the auditory cortex neuron may respond with a sustained response to a particular tone in an adequate condition if the neuron participates in discrimination of the tone.
The present experiments were performed to find conditions necessary to elicit a sustained response in the auditory cortex neuron of the cat.

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We have made experiments to find the sound stimulus which could elicit the sustained response in auditory cortical units of cats. We have already reported that the auditory cortical units were divided into three groups based upon the response property to pure tones and bands of noise; PT units (which responded better to pure tones), BN units (which responded better to bands of noise) and NR units (which did not respond to these two stimuli). In the present experiments, responses of BN and PT units were analyzed by making three-dimensional representation in terms of stimulus frequency, intensity and spike count elicited. Synthesized formants were applied to NR units as a possible stimulus to evoke the sustained response.

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