The function of sound barrier is to prevent the transmission of
direct sound, isolate the transmitted sound, and make the reflected
sound have enough attenuation. Therefore, the attenuation of sound
barrier is designed by using the principle of sound reflection.
Sound waves (noise) for transmission on the way, if meet barriers
(sound barriers), reflection will happen, so within the scope of a
certain distance behind obstacles to form the "shadow", the area
size depends on the size of the voice (frequency), see from this,
the noise attenuation of noise barrier is closely related with the
center frequency value. Can be seen from the diagram, due to the
high frequency sound shadow area is large, short wavelength, so the
most easy to be blocked, the second is the intermediate frequency
sound, the sound barrier formed behind the sound in the shadow of
the low frequency sound, due to the long wavelength, circling
around the barrier, it is easiest to diffraction in the past, so
the surrounding environment will produce certain effect, so the
noise barrier on its low-frequency noise sound insulation effect is
poorer, proved by actual measurement: The sound barrier has no
obvious attenuation for low-frequency sound with a frequency below
250Hz, but it has a better attenuation effect for medium and
high-frequency sound.
