抄録
This report describes the experimental study of acoustical characteristics of gas jet noise through the straight nozzles, whosc diameters are 0.28mm to 1.00mm.
Jet force and noise level are measured under the range of pressure from 1 to 60 atg at nozzle inlet.
The obtained results are as follows;
1. Overall sound pressure level and A-weighted sound pressure level rise simply with increase of the pressure ratio.
2. Values of the A-weighted sound pressure level can be expressed well as a function of d2·Δp√To, where d is nozzle diameter, Δp is pressure difference between nozzle inlet gas and atmosphere, and To is nozzle inlet gas temperature.
3. Maximum value of the directivity of the gas jet noises is obtained at 30° to the jet flow axis. Noise levels at the discrete frequencies of 1.25, 2.5, 4.0, and 16 kHz, are lowered at 55° to the jet flow axis.
4. The gas jet noises are lowered slightly at the ratio of length to diameter 4: 1.
