Sound Pressure Level

The sound pressure level L_p is given by

(3.22)

where p_ref is the reference pressure, p_ref = 20 μPa = 0.00002 N/m² (= 0.0002 μbar) for air. This reference pressure was originally chosen to correspond to the quietest sound (at 1000 Hz) that the average young person can hear. The sound pressure level is often abbreviated as SPL. Figure 3.4 shows some sound pressure levels of typical sounds.