maximum sound level versus slant distance, Lmax(d)
time integrated level versus distance for the reference airspeed, LE(d), and
unweighted reference sound spectrum at a slant distance of 305 m (1 000 ft), Ln,ref(dref) where n = frequency band (ranging from 1 to 24 for 1/3-octave bands with centre frequencies from 50 Hz to 10 kHz),