Noise Generated by a Power Loom

Noise Generated by a Power Loom By Sadao Aso, Rikuhiro Kinoshita, Heihachi Uematsu and Kiyohumi Sasaki, Members,TMSJ Faculty of Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo Basedon Journalof theTextile Machinery Society of Japan, Transactions,18, T13-19 (1965) Abstract An investigationwas made to survey the actual noise level generated by a power loom, devise some method to reduce the noise level on the power loom and explorethe possibilityof controllingthe noise generated by loomsin a factory. A power loom was placedin a room, 494M3 in volume,of the workshopattached to our university. The mean value of six room-constantsobtained in variousoctaves band measured 152m2. The noise level and the octave band sound pressure level were measuredwith a sound level meter, an octave band filter and a level meter. Equal-level contours of the noise level and the sound pressure level were drawn with these instru- ments. The noise level at a height of 150cm reached a maximumof 90 phons. The noise within about 2 meters from the loom was louder on the diagonalline, but at 2 meters or a longer distance from the loom it was regarded as a point source. The frequencycharacteristic of the sound pressure level showed a peak value in the 1600-3200c/s band. Sound power in the band was 11 milliwatts. A piece of gum was stuck on the surface of the stopper and a spring was replaced with a suitable one to reduceimpulsive. Then the noise made by the pickingmechanism decreasedby 4-5 dB in a high-frequencyrange. After the gearing was insulatedwith a cover, the noise radiated by the gearing in the driving part decreasedby 4-8 dB in a middle and a high-frequencyrange. This indicatesthat the noise generated by a power loom can be reduced considerablyby a completeadjustment of the loom and by insulating the sound source. 1. Introduction level generated by a power loom and computes sound power. It also explores noise sources, describes a few methods to eliminate and insulate noise and discusses The problem of noise has been around for so many the effects of those measures. years, but it is only in recent years that the need to measure noise by machine and combat it has been 2. Characteristics of Noise taken up seriously. Tokita's[1] published work of 1963 gave the results of measurements of noise generated by many kinds of machines and suggested ways to 2-1. Method of Measurement control noise generated by some of the machines. There (a) Loom surveyed is also a published work[2] on noise levels in various Hatsuya's silk loom, having 2 shuttle boxes on one kinds of factories. Then, too, there is a published side and capable of 146 rpm, was chosen for our study. general survey of noise[3). The loom's reed space was 58.5 cm long. This loom An analysis of noise in a weaving factory was was laid on square logs (5.5 cm ><5.5 cm) at a fixed made, too. Hirayama and others[4] reduced the noise place in the workshop which will be described later. A level architecturally and acoustically by covering the motor (1 IF, 3.5 A and 1400 rpm) was also laid on the ceiling of a factory with some absorbents. Nakamura logs. The loom was worked by belt transmission and others[5] studied the acoustical properties of build- through the medium of a pulley on the way. The loom ings in a weaving factory for noise control planning. was kept in a state of perfect balance to be free from We made our investigation to eliminate and pre- shakes during operation. What is referred to in this vent noise generated by textile machinery proper. This article as a "whole operation" is an operation without article measures the noise level and the sound pressure a vertical motion of shuttle boxes, healds or warp yarns Vol. 12, No. 1 (1966) 23 and with an empty shuttle having no weft yarn on it. (b) Workshop Our experiment was made in a room of the workshop attached to the Faculty of Engineering, Tokyo University of Agriculture and Technology. The floor of the room is 81 m2 (9m x 9m) in area and is built of concrete. Its roof is built of wooden boards under sheet zinc. There is no ceiling. The four sides of the room are mortar walls panelled with boards. Two sides have no windows and are trapezoid. The other two have windows and are rectangular in shape. These areas are given in Table 1. The volume of the room is 494m3. Table 1 Areas of Various Parts of the Room (m2) Fig. 1 Measuring points in the room By substituting reverberation time T, obtained from the reverberations, into the following equation, the average absorption coefficient a in the room was cal- Table 2 Acoustical Characteristics of the Room culated. Room constant R was computed by a. T= -0.162V/{S log e (1-a) } R=aS/(1-a) where V is the volume of the room and S is the whole surface area inside the room. This equation ignores sound absorption by air. (c) Method of Measuring Noise[7] To know this distribution of noise around the loom, the noise level was measured at various measuring points with a sound-level meter of Rion Co. s' make (comforming to Japan Industrial Standards C1052 and capable of measuring noise levels) by characteristics A, B and C.[8] Next, the sound pressure level in various octave bands was measured by connecting the sound level Table 2 gives the reverberation time, the average meter with an octave band filter and a level meter. absorption coefficient and the room constant of the Because their values fluctuated at each measuring room, which were measured with a sport pistol as a point, i.e., the indicator of the meter vibrated consider- sound source.[6] The pistol was fired at one corner on ably, the mode of greater values was regarded as the one diagonal line on the floor and the sound was re- maximum, the mode of smaller values as the minimum. corded at the other corner. Then the pistol and the Greater or smaller values varied within 3dB and the recorder were replaced and the sound was recorded again. modes were fixed by eye measurement. The sounds of the pistol on the other diagonal line The measuring points are illustrated as the grid in were recorded by the same method. Fig. 1. At each measuring point the height of a micro- Frequency analysis of the sounds of the pistol phone was varied to 50, 100, 150, and 200 cm. A mea- was made with an octave band filter. The reverbera- suring point is described as (e. 9.50) in this article. tions were recorded on a chart by a high level recorder. No measurement was made on the right-hand side or 24 Journal of The Textile Machinery Society of Japan lower side in Fig. 1 because many parts of machines were laid about 30 cm high. A total of 324 points were measured. The measurement was made at night when the back ground noise was small. The difference between the noise generated by the loom and the back ground noise exceeded 10 dB. Therefore, measured values for the back ground noise were not corrected by the JIS method. (d) Results of Measurement The measured values at point (e, 9) are given in Table 3 as an example of the measured results. B - and C - characteristic values of the noise level at each measuring point are nearly smilar, but A-characteristic value is about 1 phon bigger than B and C. The difference between the maximum and minimum values of the noise level varise from point to point but is below 9 phon. The difference in the sound pressure level is below 10 dB. The measured values of the noise level were written down at all measuring points in Fig. 1. The points having almost the same values were linked so that an equal-level contour was drawn. Figs. 2-4 show equal-level contours for noise levels differing in height and were drawn from the maximum Fig. 3 Equal-level contours of noise level (phons) value of C-characteristic. i at 100cm height) Fig. 2 Equal-level contours of noise level (phons) Fig. 4 Equal-level contours of noise level (phons) (at 50cm height) Solid lines are for 150-cm height Dotted lines are for 200-cm height Vol. 12, No. 1 (1966) 25 In the light of these figures, we may say that the noise generated by a loom is the compound of the sounds generated by many parts of the loom. The noise level contour of a plane 100 cm high shows directivity distinctly. Noise within a about 2 meters from the loom is louder on the diagonal line. Noise at a distance of more than 2 meters is regarded as a point source. The maximum value of the noise level at the level of the human ear is about 90 phon. The equal-level contours of the sound pressure level were made by the same method as the noise level. To cite an instance, Fig. 5 shows the equal-level contours of the sound pressure level in the 1600-3200 c/s band and on a plane 50 cm high. The sound pressure levels in each octave band at the point (e. q) closest to the front of the loom are given Table 3. All the equal-level contours of the sound pressure level showed that the sound was the loudest in the 1600-3200 c/s band, the second loudest in the 3200-6400 c/s.

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