It is measured as OSPL90 and refers to an input sound pressure level of 90 dB and one or more specified frequencies. For this measurement, all gain settings are set to the highest gain. As a rule, the measured OSPL90 values are identical to the saturation level. In addition to the classic OSPL90 value, there is also the HFA-OSPL90 value, High Frequency Agrage (HFA), at higher frequencies. This is the average of the OSPL90 values at 1 kHz, 1.6 kHz and 2.5 kHz.