In practice, complex vibrations of multiple objects often occur at the same time. This sound is often composed of many components with different frequencies and intensities. The vertical lines corresponding to each frequency component in the spectrum are arranged very closely, and there is no prominent frequency component. In such a spectrum, sound energy is continuously distributed in a wide frequency range and becomes a continuous curve, which is called continuous spectrum. The frequency components of this continuous spectrum do not have a simple integer ratio relationship with each other, and it does not sound musical. The frequency and intensity of this sound vary randomly.
