Volume, tone, and timbre are three subjective quantities that reflect the characteristics of sound, collectively reflecting the human ear's perception of sound,

The tone reflects the subjective perception of the human ear towards the pitch of the sound. Although the pitch size is also related to other factors such as sound pressure,

But it mainly depends on frequency. So generally, the higher the frequency, the higher the tone, and conversely, the lower the frequency, the lower the tone.

The frequency determines the pitch, so the detection of pitch is mainly based on the detection of the fundamental frequency, which is the study of the pitch period.

The system adopts the traditional autocorrelation fundamental frequency detection algorithm, which is based on time-domain analysis theory,

It has the advantages of simplicity and low computational complexity, and can directly calculate the autocorrelation function of the time-domain signal sampling value.

Volume reflects the amplitude of sound signals, and the amplitude of sound waves determines the level of volume. The volume of different music signals varies,

Therefore, when using volume as a signal to control the operation of the water pump, there will be ups and downs in the water column. But if the volume signal is not processed,

When the amplitude of sound waves is relatively large, there will be significant changes in the water column; On the contrary, when the amplitude of the sound wave is small, the change in the water column will not be very significant.