SOUND SILENCING APPARATUS

PURPOSE:To reduce air pressure sound occurring at the outlet end of a tunnel by a method wherein compressional wave in the tunnel is detected by a pressure gauge, and negative pressure wave for offsetting the compressional wave is produced on a signal outputted on detection by the pressure gauge and operated by a control device by negative pressure producing devices provided at the outlet end of the tunnel. CONSTITUTION:A sound silencing apparatus is constructed of negative pressure producing devices 5 provided at the right and the left of the outlet end 10 of a tunnel 01, a pressure gauge 7 that detects compressional wave 9 in the tunnel 01 and outputs signals based on the detection, and a control device 6 that calculates the time of emission of the compressional wave from the outlet end 10 and controls driving signals to be sent to the negative pressure producing devices 5. The compressional wave 9 produced by a train 04 entering the tunnel is detected by the pressure gauge 7 and the signal outputted therefrom is sent to the control device 6. Then operation is made by the control device on the signal inputted thereto to calculate the time when the compressional wave is emitted from the outlet of the tunnel 01. Then an instruction is given by the signals to the negative pressure producing devices 5 for starting the operation. Thereby negative pressure wave 8 for offsetting the compressional wave 9 is produced, resulting in silencing of air pressure sound on the outlet end 10.