Effects of close interfaces of the components of a bolt-clamped Langevin type longitudinal transducer(BLT transducer)i. e. , metal(duralmin)blocks and piezoelectric elements on its performances are examined. It is found that a surface roughness of 1μm is enough to obtain high mechanical Q-factor and high performancies when each of these surfaces is lapped to be flat. The mechanical Q-factor of various configurations of BLT transducer is measured also as a function of temperature in order to find out good one which shows little change of mechanical Q-factor due to temperature change.
In this paper, a new unified method for estimating the representative noise evaluation index L_α(α=5, 10, 25…)of the road traffic noise in the case when various traffic controls are carried out to maintain the quiet environment(e. g. , near the hospital and school)in the large cities has been introduced on the basis of the observed evaluation value L_α before practicing traffic control. More concretely, the above method has been derived from two types of typically different viewpoints in the following:(i)A direct way of evaluating the effect of the traffic control on the noise evaluation has been given under the first introduction of the equivalent model on road traffic noise reflecting explicitly an effect of the change of traffic flow owing to the traffic control. Then, the change of noise level distribution has been quantitatively estimated by use of this model(See §2. 1). (ii)An indirect way of evaluating the effect of the traffic control on the noise evaluation has been given under the first introduction of a unified expression of the probability density and/or cumulative distribution functions of traffic noise, in the form of orthogonal and/or non-orthogonal expansion series reflecting concretely the change of the traffic noise based on traffic flow control in each coefficient(See §2. 2). Furthermore, by applying the results of this theory to the traffic noise data actually observed in Hiroshima City, the partial legitimacy of this method has also been experimentally confirmed.
A method of approximately calculating the sound fields radiated by an arbitrarily shaped vibrating body was investigated. The diffraction of sound around an arbitrarily shaped vibrating body was considered with Kirchhoff's formula, modified by the directivity of a point source on a sphere, because it was considered too difficult to calculate the directivity of a point source on the vibrating body. The sound fields of the rectangular model source were obtained with the directivity of a point source on a sphere which had the same volume as the model source. The sound fields which were obtained in calculations itself agreed well with the experimental fields. The sound field was calculated using the measured directivities of a point source placed alternately at two points on the surface of the rectangular model source. The result obtained agreed with the experimental result.