Noise and airflows in five types of valves were measured and the power level of the noise radiating from a valve outlet was experimentally related to the mechanical power of the air stream through the valve. The mechanical power W_m of an isentropic flow through a valve can be calculated by equation (1), where G is the weight flow of air, C_p the specific heat with constant air pressure, T_<1T> the total temperature in inlet pipe, P_<2S> the atomospheric pressure, P_<1T> the total pressure at valve inlet and K the ratio of specific heats. In order to determine W_m, the upstream temperature and pressure T and P, the differential pressure across the orifice plate ΔP and the total pressure P_<1T> were measured over a wide range of weight flow and of pressure differential across the valve as is shown in Fig. 1. Acostic power W_a was determined as follows. Octave band sound pressure levels were measured in an anechoic room as six points on the hemispherical surface of radius 1. 8m with the origin at the valve outlet. The acoustic power W_a was calculeted by equation (2), where L_p is the mean sound pressure level averaged over six points and r(1. 8m) is the radius of the hemisphere. In Fig. 4 and 5 acoustic power W_a as a function of mechanical power W_m and the conversion efficiency η=W_a/W_m from mechanical power to sound are shown with the total pressure as a parameter. In Fig. 6〜8 some properties of η are summerized. η varies in the order of 10^<-5>〜10^<-4> for ball valve and 10^<-6> for diaphragm valve and is constant for higher total pressure but at low pressures the values are different according to the type of the valve. It was only for ball valve that the peak value of η nearly coincided with the critical pressure. Sound power level increases rapidly up to a constant at about 2. 5kg/cm^2a and doubling the weight flow of air at constant pressure may increase the power level by as much as 5 dB (Fig. 9, 10). As is shown in Fig. 11 and 12, the shape of the power spectrum does not depend on the weight flow of air but on the total pressure at valve inlet, especially for high frequencies. The sound power level of the valve noise can be calculated from equation (3), under the assumption that the efficiency η is expressed by equation (4), where n and k are constant. Values of n and k of the equation were determined for each type of valves from the experimental values of η as is shown is Fig. 4 and 5. By substituting the values of n, k(Table 1) and equation (5) into equation (3), empirical formulae for each type of valves were obtained.
This paper deals with the generation of aerial intense ultrasound field and its applications (such as the agglomeration of an aerosol and sonic drying). We could generate an intense ultrasound field (160 dB at about 20 to 28kc/s ia n chanber. By coupling a magnetostrictive vibrator with a metallic exponential horn in longitudinal half wave resonance provided with a higher mode flexural vibration plate. (See Fig. 1) Let a sound level be expressed by the airthmetic mean value of the maximum sound pressure of standing waves in the axial direction of the chamber, and it increases with increases of the area and the amplitude at the center of the plate. On the other hand, it decreases with an increase of the capacity of the chamber. (See Fig. (4, 5) It also decreases with a rise of temperature in the chamber. (See Fig. 7, 8) Then, we applied the intense ultrasound field to the agglomeration of an aerosol and sonic drying from which satisfactory effects were obtained noiselessly. In the experiment of smoke agglomeration, a tube made of acryl with a thickness of 4 mm, an insede diameter of 60 mm and a length of 1000 mm was used as a chamber. We measured the relation between the degree of agglomeration and the flow speed of an aerosol in the chamber. The aerosol was incense stick smoke. The degree of agglomaration was calculated from the output of a photo-cell densimeter. (See Fig. 16, Eq. 2) It was found from this experiment that the longer the retention time of the aerosol in the retention time of the aerosol in the chamber and higher a sound intensity level were, the higher the degree of agglomeration was. (See Fig. 17) As for the experiment of sonic drying, a sponge of vinyl chloride and silica-gel grains were used as test pieces. An apparatus for the former test piece is shown in Fig. 18 and one for the latter is shown in Fig. 19, 20. As the result of this experiment, drying time and the final water content were found to be less than those by air flow drying. (See Table 2, 3) These experimental results show the same effect as in audio frequency ranging from 0. 6 to 5 kc/s. (See Table 1)
In Tokyo the whole city part is classified into four zones, i. e. residential, commercial, limited-industrial and industrial, according to the town-and-city planning. In the above mentioned four zones and suburban zone, 17 typical areas (each about 100, 000m^2) were selected and the noises (out of door) were measured at 20 points in each area. for two months beginnig with Dec. 1965. At each point sound levels in dB(A) were measured by a sound level meter, 50 times at intervals of 5 seconds and medium and the range were obtained statistically from these 50 data to represent the noise level distrbution. These procedures are in accordance with the Japanese Industrial Standard JIS Z-8731"Methods of Measurement of sound levels". Fig. 1 and Tab. 2 show anexample of the detailed data and the average sound level at 20 points in a commercial zone. Other results are shown in Fig. 2 to Fig. 8, Tab. 3 gives the summarized result. Tab. 4 is a comparison of sound levels obtained by different methods of selection of measuring points, where one is arbitrary and another random in the same area. The meaning of arbitrary and randorm selection is as follows. In arbitrary selection the observation points were selected so as to represent the general level of noise in the area. In random selection the points were determined by a purely statistical method on the map as is shown in the figure. Main results are as follow. (a)Residential zone:Average sound level is about 50 dB(A). That makes little difference between 3 classes (A, B, C of Tab. 1) classified by the average residential site area. Sound levels are estimated to be under 50 dB(A) in 2/3 of the area of this zone. (b)Commercial zone:In this zone the sound levels are generally high(64dB(A) in average), often becoming as high as 80dB (A) or over on tram way roads. (c)Limited-industrial zone:The sound levels are usvally high in the vicinity of factories, but the traffic volume is not large in comparison with commercial zone and the sound levels are a little lower. In 50% of the area the sound level is under 60dB(A). (d)Industrial zone:The average sound level slightly exceeds 60dB(A). But there is no significant difference between industrial and limited-industrial zones. (e)Suburban zone:The average sound level is under 45dB(A). It may be noticed that there is a remarkable difference between urban and suburban zones mainly due to traffic noise.
In each zone defined in the 1st report:i. e. residential, commercial, limited-industrial, one measuring point was selected where sound levels were measured at intervals of one hour through out a whole day (24 hours). At one of the most crowded crossing roads of Tokyo(Hibiya-crossing), the same measurement was repeated. Fig. 1 and Fig. 2 show the variation of sound levels in dB(A) in the day-time. To supplement the above measurement the sound levels were measured at four points in each zone and the noises were magnetically recorded four times in a day(in early morning, in forenoon, in afternoon and at night). The recorded sounds were analyzed to obtain the sound spectra. Fig. 3 and Tab. 1 show the results obtained of course, the sound level in the day-time was much higher than in the night everywhere. And it has become clear that the variation of sound level in the night was characteristic of the zone. For example, the noise durations in which sound levels exceeded 45 dB(A) are remerkably defferent:9 hours(20 to 7 o'clock) in residential zone, hours(1 to 6 o'clock) in commercial zone, 7 hours(23 to 6 o'clock) in limited-industrial zone and 0 in industrial zone. The measured noise levels in busy crossings exceeded 60 dB(A) during the whole day. Fig. 4 shows the sound spectra at every measuring point and time. In geneal, the spectra show a similitude among themselves.