Perceived Level of Sonic Boom Noise: Recommended Computation Methods, Rationale, and a Minor Modification

Analysts face algorithmic choices when writing software to compute the Perceived Level (PL) noise metric. This document contains algorithmic recommendations for computing the PL of a sonic boom waveform. For the four main computational steps, the recommended algorithm and a less accurate alternative are introduced. Rationale for each recommendation is provided by comparing levels returned by the recommended algorithms versus the alternate algorithms while discussing the expected accuracies of each. Algorithm evaluations are performed using as input predicted shaped sonic boom waveforms for the X-59 aircraft and background noise waveforms measured in a community. A minor addition to a data table used to weight the loudness spectrum while summing to total loudness is also described here; that weighting is a precursor to the Perceived Level value. This table addition, which fills a gap at low sound levels, should increase the accuracy of PL values for quiet background noise and evanescent waves in the Mach cutoff shadow region.