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Implementation of inverse transfer functions using NLMS algorithm for reducing a sound reverberation in the tunnel

For reducing a sound reverberation in a real tunnel, we found transfer functions by experiment in the tunnel and applied the inverse transfer functions to the sound sources from the speakers installed in the tunnel. The speakers were installed every 50 meters in the tunnel and it was assumed that the sound reverberation has a range of 300m, which need to consider only 7 speakers and 7 target locations. Because of it, we found the transfer functions of 49 paths and applied the sounds with inverse transfer functions to each speaker. To obtain the inverse transfer functions effectively, we used a NLMS algorithm and proposed method. The results are shown in simulations and the real recording in the tunnel.