Validating the Doubling-Diameter Method for Rig-Noise Detection in Jet Noise Measurements

Initial boundary layer state of typical model-scale jet nozzles and its impact on noise

“…He showed that the normalized amplitudes of sound pressure level spectra reported by Tanna 8 were higher relative to the data at same operating conditions taken in a Boeing facility (Low-speed Aeroacoustic Facility (LSAF), 7 ). Figure 1, reproduced from 7 (also discussed in 5 and 9 ), illustrates the difference between the data of Tanna 8 and that from LSAF. 7 The Tanna data are consistently larger in amplitude on the high-frequency end.…”

“…They demonstrated this by measuring noise with nozzles of different diameters and checking that the intensity variation followed expected theoretical trends as well as by measuring noise with and without a muffler in the upstream duct. 9,43 The muffler did not make a difference in the noise, thus, demonstrated the absence of significant rig noise. They then conducted noise measurements for 'ASME' and 'Conic' shapes (as in 15 and 5 ).…”

“…Harper-Bourne, however, recalled that extensive internal silencing was performed in that facility and rigorous tests were conducted to validate its quality. Recently, Karon and Ahuja, 9 conducted further tests in the Tanna facility (now in their custody) to rule out rig noise, as discussed further in the following. With regards to the University versus Industrial type facilities, Harper-Bourne noted that the University types, exhibiting higher noise, had large contraction ratios.…”

“…On the experimental side, BL measurements were performed by Karon and Ahuja. 9,43–45 These experiments were conducted in the same facility where the Tanna data, 8 exhibiting higher noise in Figure 1, were acquired. Authors first went through measurements to disprove that rig noise was a factor.…”