This tuning method which do not require tuner's hearing sensation is well improved to bring high efficiency for the tuning works in a piano factory, but still there is a dissatisfaction as follows;This method takes 0. 2sec to one accurate observation at shortest, but many treble tones have their duration shorter than 0. 2sec. Thus , tuning evaluation is difficult and inaccuracy. Therefore;the following improved procedure is examined. Since the frequency deviation detector shows the same count number to any tones which have same pitch deviation, when no deviation the number set to be equal to a frequency in the middle range tone. And this detector is connected to the digital synthesizer for D/A conversion. Since this synthesizer generates a signal which is the same frequency as the count number, observe this signal as a substitute for the real signal. Thus, it is possible to tune any tones, by converting them to a middle tone. According to the above procedure, a trial tuning device for practical use is set up and sufficient results are obtained.
This paper describes augmentation of capacity for a sound source (20kHz) with a rectangular vibration plate in the stripes mode for airborne ultrasonics by using reflection plates. When two reflection plates are placed parallel to both sides of a vibration plate which radiates plane waves in the air, the radiation resistance on the vibration plate is cyclically changed by varying a distance between the vibration plate and two reflection plates. Compared with the free field, the maximum value of the radiation resistance is large and the minimum value is small. In a case where two more reflection plates are inseted perpendicular to the vibration plate at a suitable distance from the center of the vibration plate, the maximum value of the radiation resistance is sharply increased compared with the free field. Making use of this relation, electric power supplied to the ltrasonic source at a constant vibration amplitude is also increased correspondingly the change in radiation resistance, so that the acoustic output power is increased about four or six times more than that in the case in free field. Moreover, using this ultrasonic source, a high intensity ultrasonic field (164 dB) is easily produced in a rectangular vessel.
Recently, for the purpose of reducing a living environmental noise, many sound insulation systems are very often improved acoustically by changing their geometrical scales and/or acoustic characteristics. In this paper, new identification and probabilistic prediction methods for these insulation systems are theoretically proposed in a practical expression form under introducing a few functional parameters supported by many of physically structual factors, in close relation to the well-known statistical energy analysis method, especially when the sound characteristic is changed by the above improvement work. Further, these functional parameters introduced only for the prediction are easily estimated in the preliminary experiment by use of the well-known least-squares type error criterion, under the coexistence of a background noise. Finally, the effectiveness of the proposed prediction method has been experimentally confirmed too by applying it to the actually observed data on a single-wall type sound insulation system.