Software to compute loudness levels of sonic boom noise with an optional correction for ambient noise contamination.

About this technology

Overview

Several software algorithms are implemented as Matlab code to compute the loudness level of an array of sonic boom waveforms that are input to the code (named Narrow-band Octave-band Metrics, or NOM for short). The following quantities are computed and returned by this software for each of the input waveforms: loudness level metrics PL, PNL, ASEL, BSEL, CSEL, DSEL, ESEL, GSEL, ZSEL, ISBAP; the weighted sound pressure levels LAF_max, LBF_max, LCF_max, LDF_max, LEF_max, LGF_max, LAS_max, LBS_max, LCS_max, LDS_max, LES_max, LGS_max; the weighted sound pressure time histories LAF, LBF, LCF, LDF, LEF, LGF, LAS, LBS, LCS, LDS, LES, LGS; the loudness spectra in units of sone; the fractional-octave band sound pressure level spectra. An ambient noise correction can be applied using methods outlined in ISO 11204:2010(E) Sections 5.4.2 and 7 using either of the two accuracy grades documented within that standard or also several methods based loosely on that standard but that have been customized for this application - sonic boom signals. The loudness level metrics and spectra noted above are returned by the software with option to exclude from the output metrics and spectra that are of no interest to the user. Finally, an optional, user defined offset can be applied to the one-third-octave band spectra prior to computing the loudness levels of the input waveforms to mimic the effects of frequency dependent signal attenuation.