high frequency average (hearing aid) (HFA)
The hearing aid measurement technology and its characteristic values are listed in DINIEC 60118.
The test procedures for hearing aids are concerned with sound pressure( SPL), output sound pressure level ( OSPL), maximum gain (FOG), average gain and gain control. As for the frequency-dependent average gain value, the High Frequency Average (HFA), IEC 60118 is about the average gain value or sound pressure in decibels at the three specified frequencies of 1.0 kHz, 1.6 kHz and 2.5 kHz.
In addition to the characteristic value for the average value of high frequencies, there is also the special purpose average( SPA).