APPLICATION OF SOUND-ABSORBENT PLASTIC TO WEAK-SHOCK-WAVE ATTENUATORS

A device for attenuating weak shock waves propagating in a duct has be en developed utilizing sound-absorbent plastic which is usually used f or attenuating sound waves. The device has a tube made of the sound-ab sorbent plastic installed coaxially to a surrounding metal tube with a clearance between them. The clearance acts as an air layer to enhance the performance of the shock wave attenuation. When a weak shock wave propagates through this device, the pressure gradient of the shock wa ve is gradually smeared and hence its overpressure is decreased. The p erformance of the device was examined using a 1/250-scaled train tunne l simulator which simulated the discharge of weak shock waves created by high-speed entry of trains to tunnels. The overpressure of the shoc k waves ranged up to 5 kPa. The shock wave overpressure was decreased by 90% with the present attenuator attached. This device can be applie d to various industrial noise suppressions which are associated with u nsteady compressible flows. (C) 1998 American Institute of Physics. [S 0034-6748(98)03804-0].