1. was suppressed with a tab (see ;';Thedataencompasses an operating range of plume Mach numbers Mj from 1.17 to 1.67 (2. As pointed Out by Ffowcs Williams many years ago the prediction for total acoustic power radiated from,prbo jet engines of military power (circa 1950 ) cannot be estimated from Lighthill's famous eighth power law. Instead for these engines one needs to consider the more efficient noise production mechanism due to supersoni ally convecting distutbances which Phillips" termed eddy Mach wave radiation. Figure I shows an example of the radiat-d near acoustic field for this mechanism. As discussed in the introductory remarks, current and future research efforts are being directed to obtain a better understanding of the phenomenon since it would clearly be active in the noise field Of high performance military aircraft and second generation space transportation vehicles. For these class vehicles the mechanism would dominate acoustic radiation within the Mach cone of figure 1. which for most applications involve 4 a substantial portion of radiation in the jet plume quadrant.
3. The Acoustic Analogy—Thirty Years On