With the synchronous trigger of the reference frequency ƒ_s Hz suitable to a stretched scale, the observed fundamental wave of the piano sound moves at the rate of the deviation frequency on the CRT screen. The direction of the movement gives that of the pin rotation for tuning and the velocity of movement also does the tuning angle. The result of the pitch deviation with decision time of 0. 2 second represents that the lower limit of a deviation δ (cent) in the bass section is inversely proportional to ƒ^2_s and the upper limit in the treble section is inversely proportional to ƒ_s. Therefore;1) In the bass section the CRT tuning method is better used in the frequency range above 110 Hz where the resolution is high and observed with multiples of a detected fundamental wave. 2)In the treble section this method is better applied in the frequency range below 261. 6 Hz where the observable upper limit of deviation is 50 cent, and observed through a frequency divider. Consequently a trial tuning device for practical use is set up and satisfactory results are obtained.
The initial stages of the generation of impulsive sounds caused by two types of electric discharge ; which were the spark discharge and the wire explosion method, were observed by a high-speed photographic recording system combined with the schlieren method. The shapes of the shock front and the propagation velocity near the electrodes were observed using there schlieren photographs. In the sense of sight, it was found that the wave front of impulsive sound generated by the spark discharge using the small gap showed a spherical shape and a sound was generated nearly at the time when the discharge current began to flow. It was also found that the shock fronts produced by the wire explosion method showed the cylindrical shape. The propagation velocity of the shock near the electrodes was measured and the increase of the propagation velocity caused by the highly intensive nonlinearity was recognized. The shock amplitude was estimated by using the observed propagation velocity.
The stationary sound level is measured as the point of subjective equality (PSE) to the randomly fluctuating sound in loudness discrimination. The fluctuating stimulus is specified with two parameters : fluctuating width and velocity. These are obtained from the distribution curve of the stimulus sound envelope. The stimuli presentation are carried out using stochastic approximation method where the level of the stationary sound is varied sequentially in each test based on the observation of each response. As a result of these tests, a PSE is roughly estimated. The final step is to determine a more accurate PSE through numerical techniques. The results indicate that subjects hear sounds louder as the fluctuation width and velocity are relatively increased. A nonlinear temporal integration model is used to simulate the hearing system. Several frequently occuring levels appear in the model's output (a model of loudness) distribution curve. The average of these levels closely correlates to the calculated PSE.