Related introduction:

There are certain standards for the level of each tone in the music system. The standard height of sound varies from generation to generation. The international standard height (the first international height) is an A sound that vibrates 440 times per second.

There is a unified pitch standard in the world, which is convenient for music theory research, musical instrument making and cultural exchange. The C sound, which vibrates about 26/kloc-0 times per second, is called the central C in the music system and is at the top of the basic level.

Extended data

A world-wide system in which a group of tones (octaves) is divided into twelve semitones and the ratio of vibration numbers of two adjacent laws is completely equal. The law of twelve averages refers to dividing an octave into twelve equal parts according to the frequency proportion, and each equal part is called a semitone second degree. Sophomore is two equal parts. ?

There are some amazing coincidences in dividing an octave into 12 equal parts. The frequency ratio of two tones in their pure fifth interval (that is, the seventh power of 2/12) is very close to 1.5, and the human ear can hardly hear the difference between the fifth interval of "five-degree mutual law" and "twelve-degree average law". The law of twelve averages is widely used in symphony orchestras and keyboard instruments, and now the piano is tuned according to the law of twelve averages.

Baidu encyclopedia-standard sound