Sound barrier of municipal viaduct Sound barrier of municipal viaduct Sound barrier of municipal viaduct
The determination of the design target value of the sound barrier is related to the road traffic noise value at the sound receiving point (measured or predicted), the background noise value at the sound receiving point and the standard value of environmental noise.?
If the background noise value of the noise receiving point is equal to or the noise barrier of the municipal viaduct is lower than the standard value of environmental noise in the functional area, the design target value can be determined by subtracting the standard value of environmental noise from the road traffic noise value (measured or predicted).
Since the data given in this design are actual measured values, the design target value is the difference between the road traffic noise value and the environmental noise standard value.
Since the object to be protected in this design is the teaching building, the noise at night will not affect the staff's learning, so the measured value at night will not be considered. The target value of noise barrier design can be determined by the road traffic noise value, which is known from Table 1-1,
Noise value of S1 point
(3-1) Where:
N - number of test data;
- The ith A-weighted sound level, dB; sound insulation wall of municipal viaduct
Substituting into the data in Table 1-1, the noise value of S2 point is the same, and the noise value of the noise source is obtained through superposition calculation.
According to the daytime loud pressure level of the prediction point measured in the design parameters is 74.0 dB, and according to the standard value of urban area noise specified in the Standard for Environmental Noise in Urban Areas (GB3096-93) issued and implemented in 1993, we know that the teaching building belongs to Class 1 area, and the standard value of environmental noise is 55 dB. That is, the design target value of the sound barrier is:
74- 55 =19dB
3.4 Location determination
According to the relative position between the road and the protected object and the surrounding landform, the setting position of the sound barrier should be selected. The principle of selection is that the sound barrier is close to the sound source, or close to the sound receiving point, or the available earth slope, embankment and other obstacles, so as to achieve the sound attenuation required by the design goal with less quantities. Sound barrier of municipal viaduct
The diffracted sound attenuation of the sound barrier can be obtained from the equivalent frequency fe. Generally, the equivalent frequency of road traffic noise, fe=500Hz, is calculated according to the following formula to obtain the approximate diffracted sound attenuation △ Ld of the sound barrier.?
When the length of the line sound source is far less than the distance from the sound source to the sound receiving point (the distance from the sound source to the sound receiving point is more than 3 times the length of the line sound source), it can be regarded as a point sound source. In this design, the distance from the sound source to the sound receiving point is 39m, which is an infinite line sound source and a finite sound barrier.
When the sound source is an infinite non phase trunk sound source, its diffracted sound
Sound barrier of municipal viaduct Sound barrier of municipal viaduct Sound barrier of municipal viaduct
