For very long supersonic aircraft the ’’midfield’’ sonic boom signature may not have evolved fully into anNwave at ground level. Thus in current boom minimization techniques the shape of the aircraft may be tailored to optimize this midfield wave form for reduced subjective loudness. The present investigation tests a family of ’’flat‐top’’ waveforms cited by Darden: all but one have a front shock height (‐pSH) less than the peak amplitude (‐pMAX). For equal subjectiveloudness, ’’flat top’’ vsNwave (peak overpressure ‐pN), the peak amplitude of the ’’flat top’’ signature was found to be substantially higher than that of theNwave; thus for equal peakamplitudethe ’’flat‐top’’ signature was quieter. The results for equal loudness were well fitted by an empirical law ‐pSH+0.11‐pMAX=‐pN; the equivalence shows how the front shock amplitude (‐pSH) dominates the loudness. All this was found compatible with predictions by the method of Johnson and Robinson.