457374.fig.0020a
(a)
457374.fig.0020b
(b)
Figure 20: FIR comb filter, delay 3 ms. (a) illustrates the comb filtering effect, when the signals have the same energy, whereas (b) illustrates the effect when the passive attenuation of the headset (at the frequency of the first notch −13 dB at 170 Hz) is taken into account.