An investigation of the noise field produced near a half-inch diameter steam jet

Abstract The near noise field of a 0·5 in. diameter unchoked steam jet was investigated, using a nozzle installation and supply line designed and constructed for the purpose. The overall sound field (25 to 40,000 c/s) and the sound fields for three representative frequencies ( 1 3 - octave bandwidth) were plotted as contours of constant sound pressure level within 60 diameters of the jet nozzle exit. These noise fields formed the basis for discussion of the jet noise sound fields and in particular, the directional trends of the noise fields at various frequencies were investigated. The noise radiation decay rates in different directions were estimated and an approximate radial limit for the beginning of the inverse square law was fixed. To find the variation of sound pressure level with jet Mach number, the distribution of the velocity exponent was plotted as a contour map. The characteristics of each sound field were compared with previous work by other investigators; particular attention was paid to the different media used. All the characteristics of the sound fields investigated were compatible with both the quadrupole and simple source theories for the generation of sound, although some of the results were contradictory to statements made in other reports.