1.1 This norm specifies the acoustical design and acoustical property measurement method of noise barriers.
1.2 This norm is mainly applicable to such projects as urban roads and track traffic, and the noise barriers erected at other outdoor sites, such as highways and railways may also be made reference to this norm.
2 Normative References
The following standards and codes contain provisions which, through reference in this text, constitute provisions of this norm and are equivalent to this norm.
GBJ 005-96 "Specifications for Environmental Impact Assessment of Highways"
GBJ 47-83 "Acoustics-Sound-absorption Coefficient Measurement by Method of Reverberation Room"
GBJ 75-84 "Acoustics-Measurement of Sound Insulation in Buildings-Specifications"
GB 3096-93 "Standard of Environmental Noise of Urban Area"
GB 3785-83 "Sound Level Meters"
GB/T 3947-1996 "Acoustical Terminology"
GB/T 14623-93 "Measuring Method for Environmental Noise of Urban Area"
GB/T 15173-94 "Sound Calibrators"
GB/T 17181-1999 "Integrating-averaging Sound Level Meters"
HJ/T 2.4-95 "Technical Guidelines for Noise Impact Assessment"
When the above standards and codes revised, their most recent editions shall be adopted.
3 Terms
The following terms and definitions are adopted in this norm.
3.1 Sound pressure level (Lp)
The denary logarithm of the ratio between sound pressure and reference sound pressure, multiplied by 20, and the unit is decibel (dB):
(1)
Where:
p——the sound pressure, Pa;
p0——the reference sound pressure, 20μPa.
3.2 A-weighted sound [pressure] level (LpA, LA)
Sound pressure level measured by A-weighted network
3.3 Equivalent [A-weighted continuous] sound [pressure] level (LAeq, T, Leq)
Within the stipulated time limit, A [-weighted] sound pressure of a certain continuous stationary sound has the same mean square A [-weighted] sound pressure as the time-varying noise, so the sound level of this continuous stationary sound is the equivalent sound level of this time-varying noise, and the unit is decibel (dB).The Formula of equivalent sound level is:
