4. Level and phase indication

4.1 Level indicators

Short-term auditory memory is very unreliable, and the listening level depends on the gain of the power amplifier. The level meter provides an objective indication of the audio level on the storage or transmission medium. Its objectives are :

• evaluate the peak signal level to determine whether or not the PML (Permitted Maximum Level) has been exceeded. This triggers a limiter on the transmitter, and if it lasts longer than a few milliseconds, it can create audible distortion;

• estimate the speech/music balance. This is a subjective value which can be approximated by an average rather than a peak measurement. A longer time constant should then be used.