Frequency Analysis of the Sound Caused by Shedding Motion Using a Short Time Fourier Transform

Noise in weaving mills becomes much louder with increasing speed of weaving machine. One of the sources of the noise is the collision of healds caused by shedding motion on a jet loom. It was clarified in our previous report that the sound caused by shedding motion was significantly connected with heald motion during a period of shedding motion. In this report, therefore, its frequency characteristic was investigated using a Short Time Fourier Transform in order to relate the sound to the heald motion in a period of shedding motion. Power spectrum of sound showed a feature near the upper dead point of shedding motion when healds collided the heald bar. Superposing sound pressure signals during several periods of shedding motion, we found that some peaks of power spectrum were emphasized near the upper dead point of shedding motion.