Echo Cancellation
When an acoustic wave travels in a room, it reflects from the walls and hard surfaces in the room. So, the recorded signal is distorted by reflected waves from the boundaries. Removing echoes from the recorded signal is one of the main tasks in room acoustics. Synthetic Time Reversal (STR) is able to reconstruct the original source signal from distorted received signals.
To evaluate the performance of STR, a simple airborne experiment is conducted. Figure 1 shows the location of the sound source and an array of microphones.
Figure 1: Experimental set-up. The sound source and the receiving array is shown by red circles.
Figure 1: Experimental set-up. The sound source and the receiving array is shown by red circles.
A 10 ms Gaussian sine wave signal at 2 kHz is used as the source signal (Figure 2a). As shown in Figure 2b, the received signal has many echoes with only 59% correlation with the actual source signal.
Figure 2: (a) The broadcast signal, a Gaussian sine wave at 2 kHz with a duration of 10 ms.
(b) Received signal at one of the array elements. The cross correlation coefficient of this signal with the broadcast signal is 59%.
Figure 2: (a) The broadcast signal, a Gaussian sine wave at 2 kHz with a duration of 10 ms.
(b) Received signal at one of the array elements. The cross correlation coefficient of this signal with the broadcast signal is 59%.
The figure below is the STR reconstructed source signal. Here, STR provides a noticeable improvement in the signal envelope shape over the single-receiver.
The cross correlation coefficient of this signal with the broadcast signal is 95%.
Figure 3: STR estimated source signal.
Figure 3: STR estimated source signal.