With the fast urban development speed, more and more problems influence our life, and noise is one of the most significant problems, so a variety of environmental noise control standards have been introduced in China.
There are three factors to generate and transmit the noise: noise source, propagation path and receiver. Most adults can hear the noise within the frequency range of
100 Hz to 5000 Hz. The frequency of conversation and common noises in the buildings is basically 125 Hz to 4000 Hz. The wall sound reduction index STC refers to
the sound insulation capability of wall to the noise within the range of 125 Hz to 4000 Hz.
Decibel (dB) is a unit used for expressing the sound relative intensity. Physically, the defined reference acoustic pressure (P0=2×10-5 pa) corresponds to 0 Db. If the noise pressure is P, the noise decibel is equal to 20log(P/P0). So decibel is a designated unit. As the same as the earthquake magnitude unit expressing the earthquake intensity, the collapsing force of earthquake at a scale of 6 is generally low, but the earthquake at a scale of 7 may cause a great disaster.
Sound Reduction Index
The sound insulation property of material is the capability to reduce the noise intensity. If the sound of one room is 70dB, the sound transmitted to the adjacent room through the wall will be reduced to 40dB. So the sound insulation property of the wall is 30 dB.