A Loudness Calculation Procedure Applied to Shaped Sonic Booms

The economic viability of a supersonic commercial transport airplane would be much enhanced if it could fly supersonically over land. Efforts to design an airplane to produce a minimized sonic boom at the ground require knowledge of the impact of sonic booms on people. Loudness, being a fundamental and well-understood characteristic of human hearing, was chosen as a means of quantifying the magnitude of sonic boom impact on people. This paper describes in detail a procedure that can be used to calculate the loudness of sonic booms. The procedure is applied to a wide range of sonic booms, both classical N-waves and a variety of other shapes of booms. The loudness of N-waves is controlled by overpressure and the associated rise time. The loudness of shaped booms is highly dependent on the characteristics of the initial shock. A comparison of the calculated loudness values indicates that shaped booms may have significantly reduced loudness relative to N-waves having the same peak overpressure. This result implies that a supersonic transport designed to yield minimized sonic booms may be substantially more acceptable than an unconstrained design.