Figure 9
Rapid training of the LMS echo attenuation filter, shown for noise intensities of 63 dB (bottom three curves) and 83 dB (top three curves). In each case, three different normalized learning rates were tested: M = 0.001, 0.005, and 0.025. The filters achieved a suppression of roughly 30 dB. The limiting factor for the lower-intensity noise was the 32.5 dB noise floor of the microphone. The adaptation process works well with 65 dB noise, a learning time of 1–2 s, and a normalized learning rate of M = 0.025.
