Supplementary question: What is the level level? What is his unit? What is the relationship and difference between level level and sound pressure level?

Answer: Sound pressure is the fluctuation value of atmospheric pressure generated by the vibration of the sound source. Its unit is (PA). One Pa is the pressure to obtain a force of Newton on an area of one square meter.

The sound pressure level is the level representing the size of the sound pressure. It is the ratio of the actual sound pressure at the test location to the standard sound pressure, which is the logarithm of 10 as the base, multiplied by 20. The unit of the sound pressure level is decibel (dB). Sound pressure and sound pressure level are objective physical quantities of sound source.

Loudness represents the loudness of a sound, and its unit is (Song Dynasty)

Loudness level is the level representing the loudness of a sound. It is (square) in the unit. Loudness and loudness level are subjective perception values, which are obtained through subjective evaluation.

Explanation: Sound pressure level and loudness level are the main commonly used units for measuring sound size. Sound pressure level and loudness level are both related and different. When the frequency is one kilohertz, the value of sound pressure level and loudness level are equal. If the frequency is higher or lower than one kilohertz, the sound pressure level and loudness level will be different. Their change relationship can be analyzed by the loudness curve.

With regard to the level level, it is a unit representing the size of the electrical signal of sound. It is the ratio of the voltage at the measuring point to the standard voltage. Take the logarithm with the base of 10 and multiply it by 20.

When the sound pressure level and the level level are normal in the tuning system, their changes are consistent. However, because the reference values of sound pressure level and level level are different, the variation range of sound pressure level is about 0dB~100dB, and the variation range of level level is usually about - 60dB~+40dB.