Metre, also known as volume unit meter, is an electronic indicator widely used in audio devices and systems. It is not a peak meter, but used to display the average volume level of audio signals. In audio devices, VU meter is one of the most basic tools, especially on the mixing console, which provides an intuitive way to monitor and adjust the strength of audio signals. The operation of VU meter is based on the human ear’s perception of the average value of sound. By calculating the average value of the signal, it reflects the human ear’s perception of sound loudness, thereby helping users adjust the loudness of audio signals to make them more in line with human auditory habits.