Ducts

(A) Noise Problems

Air-borne Noise

• Air flowing through ducts induces vibration at the duct wall, which generates rumbling noise. In addition, the noise inside the duct can be transmitted to the atmosphere through the duct surface. All of these may cause noise disturbance to nearby residents (see Figure 18).

(B) Practical Remedies

Air-borne Noise

• Stiffen the vibrating duct surface with supporting webs so as to reduce the movement of the vibrating surface.
• Apply damping material to the vibrating duct surface (see Figure 19) so as to reduce the movement of vibrating surface.
• Apply composite lagging of sound absorbing materials (see Figure 19) to contain the radiation of noise.
(Noise Reduction up to 20 dB(A))