The change in medium pressure is called sound pressure. The difference between the pressure P when there is a sound field in the medium and the pressure P0 when there is no sound field is the sound pressure. Since the measurement of sound pressure is relatively easy to implement, other physical quantities such as particle velocity can also be obtained indirectly through the measurement of sound pressure. Therefore, this physical quantity is commonly used in acoustics to describe sound waves. The unit of sound pressure is Pascal (pa), and its calculation formula is: Sound pressure (p) squared = Sound intensity (I) × Medium density (ρ) × Sound speed (C) Among them, the sound intensity unit is: W/m2 Density Unit: kg/m3 Sound speed: m/s The pressure change caused by vibration when sound waves pass through the medium. It changes with time, and the measured sound pressure is its effective value. The unit is Pa or MPa. The indicator indicating the size of sound pressure is called sound pressure level, which is expressed by 20 times the common logarithm of the ratio of the sound pressure (p) of a certain sound to the basic sound pressure value (p0), that is, 20lgP/P0 , the unit is dB. Practical Application: Street Noise Monitor