Axisymmetric vibrations of cylindrical tubes were analyzed by a new simple method to develop useful radiators of high-intensity ultrasound. The analysis was based on the assumption that the cylindrical tube was thin-walled, so the radial stress(σ_<rr>)was negligible. Several cylindrical tubes of mild steel were fabricated , and their resonant frequencies and displacement distributions were measured. By the experiment, it was confirmed that the analytical results could be applied to very thick cylindrical tubes of which inner-to-outer-radius ratio was 0. 6 and to long tubes. Two types of vibrations which were suitable for the radiator were found. One was the extensional radial-axial-coupled vibration and the other was the axisymmetric bending vibration. On the basis of the analytical results, we designed the cylindrical tube radiator which both sides were fixed by flanges. And the radiator was confirmed to be effective for radiating high-intensity ultrasound.
Measurements were made with test hammers of four different specifications-the combination of the Mass and the Radious-and of the Fall Height being changed at intervals within the range 1〜32cm. First the usual frequency characteristics of ⊿L were obtained by a 1/3-octave-band frequency analysis for a single impact with a multichannel analyzer operating in fast and peak-level-hold modes. Since the shape of ⊿L curves are, as is well-known, very simple and resemble to each other, it is enough to take f_0, the frequency where the curve rises up from the horizontal axis. our In addition, out results show a noticeable close relationship between f_0 and such level difference as L_O-L_A, measured with a test covering. Finally, it was found reasonable to illustrate the experimental results on a diagram of M・H・R^<-1/2> vs f_0・H^<-1/2>, that is, the properties of a sample are shown as a single curve indicating clearly the individual characteristics. For instance, the slope of the curve for carpet has a sudden change at a certain impact condition, and so-called needle-punch carpet is quite different from a usual elastic plate. A calculation diagram was introduced to estimate the impact noise reduction of floor coverings under optional conditions of free-drop hammers.
The time series of sound levels of road traffic noises observed at the site in the vicinity of a road are analyzed with respect to the time pattern. The results obtained are follows:1)The probability that a given series of sound levels will happen, is presented by a joint function of the transition probability distributions as Markov chains. 2)The stochastic quantities which represent the dynamical properties of time series of sound levels are obtained. These are the average duration time in which a given sound level is successively observed, the average duration time of the state in which the sound levels are over or less than a given level L dB, and the average recurrence time of a given sound level.
Optimization technique has been applied to designing the torsional vibrators with complicated requirements. The torsional transducer of step formed and uniform types for a mechanical filter are designed to satisfy such constraints that their equivalent inductances and capacitance ratios as well as resonant frequencies satisfy the required values. As for a step formed torsional resonator, the dimensions are determined easily by this computer method so that its weight is minimum and its resonant frequency satisfies the required value precisely under keeping the spurious frequencies of the flexural 1st and 2nd modes away far from the torsional resonant frequency by required interval. An important point for effective application of this technique to designing the electro-mechanical vibrator is that the formula for its resonant frequency is substituted into the objective function by eliminating a design parameter of one dimension, because the resonant frequency condition is a serve constraint. One designing is accomplished for only about 10 seconds by a normal sized computer. These designed values are compared with the measured ones and are made sure experimentally to satisfy the required values. This paper concludes that the optimization technique is very useful to design the electro-mechanical vibrators.