High speed flight effects on shock associated noise

An experimental study was conducted to evaluate the effects of high speed flight on shock associated noise. This study was conducted in the Lockheed anechoic wind tunnel using flow from a 4-inch diameter pipe for flight simulation and a 0.4-inch diameter flow to simulate the supersonic jet. Acoustic measurements were made in the farfield and within the flight simulation flow for simulated flight Mach numbers up to 0.8 for unheated jet Mach numbers of 1.42 and 1.49. It is shown that the peak frequency of the shock-associated noise decreases with increasing flight speed. Similarly, shock-associated broadband noise magnitude was observed to increase with flight velocity.