Harshness is a typical transient interdisciplinary phenomenon of noise and vibration.
The major frequency range for the generation of harshness is from 7 to 60 Hz for vibration, and for shock noise is from 40 Hz to 240 Hz. These ranges can be divided into two major bands respectively.
For vibration one band is that under 20 Hz, mostly due to unsprung vibrations, and the other above 20 Hz, which is primarily the effect of fore-and-aft vibrations of suspension, tyre side wall vibrations, and structural vibration of the body.
Shock noise can also be divided into two bands, 40 to 120 Hz and 120 and 240 Hz, both involving body and cavity modes.