The purity of the sound is actually determined by the signal-to-noise ratio. The higher the value, the smaller the effect of the noise floor. The key parts of an independent sound card are its integrated preamp, integrated amp, and ADDA (digital-to-analog converter). The quality of the preamp can directly affect the signal-to-noise ratio of the sound coming from the microphone, and a good ADDA can make the sound more reducible, and it can also reduce the original noise floor inside the sound card. The current independent sound card has a certain ability to improve the signal-to-noise ratio internally, and the more critical source of the noise floor comes from the recording environment, equipment, cables, etc. If there is no noise floor in the recorded signal when the sound card is not connected to any external device, you can determine that the noise floor caused by the external device during recording. At this time, the interface of the cable should be checked first. When there is a noise floor problem, then you should check the microphone for problems. After confirming that there is no problem with the microphone, check for environmental interference. For example, abnormal current instruments (mobile phones, computers, players, etc.) may generate electromagnetic signal interference and cause sound cards, Devices such as microphones have a noise floor. When the power supply is not grounded in the working environment, it can easily cause noise floor.