我们都知道,声音是机械振动的传播,必须要有振源和传播振动的介质。振源就是发声体,最常见的介质是空气,振动经介质传播到耳朵或声音检测仪中,就可以知道有声音了。不过耳朵能听到的声音只是整个声音中的一部分,一般频率在20～20000赫兹,更低频率和更高频率只能用 We all know that sound is the transmission of mechanical vibrations and that there must be a source of vibration and a medium that transmits vibrations. Sound source is the sound generator, the most common medium is air, vibration transmitted through the media to the ear or sound detector, you can know there is a sound. However, the sound that the ear can hear is only a part of the whole sound, and the frequency is generally 20-20000 Hz. The lower frequency and the higher frequency can only be used