Joint Dereverberation and Residual Echo Suppression of Speech Signals in Noisy Environments

Abstract

Abstract-Hands-free devices are often used in a noisy and reverberant environment. Therefore, the received microphone signal does not only contain the desired near-end speech signal but also interferences such as room reverberation that is caused by the near-end source, background noise and a far-end echo signal that results from the acoustic coupling between the loudspeaker and the microphone. These interferences degrade the fidelity and intelligibility of near-end speech. In the last two decades, postfilters have been developed that can be used in conjunction with a single microphone acoustic echo canceller to enhance the near-end speech. In previous works, spectral enhancement techniques have been used to suppress residual echo and background noise for single microphone acoustic echo cancellers. However, dereverberation of the near-end speech was not addressed in this context. Recently, practically feasible spectral enhancement techniques to suppress reverberation have emerged. In this paper, we derive a novel spectral variance estimator for the late reverberation of the near-end speech. Residual echo will be present at the output of the acoustic echo canceller when the acoustic echo path cannot be completely modeled by the adaptive filter. A spectral variance estimator for the so-called late residual echo that results from the deficient length of the adaptive filter is derived. Both estimators are based on a statistical reverberation model. The model parameters depend on the reverberation time of the room, which can be obtained using the estimated acoustic echo path. A novel postfilter is developed which suppresses late reverberation of the near-end speech, residual echo and background noise, and maintains a constant residual background noise level. Experimental results demonstrate the beneficial use of the developed system for reducing reverberation, residual echo, and background noise. S. Gannot is with the School of Engineering, Bar-Ilan University, Ramat-Gan 52900, Israel (e-mail: gannot@eng.biu.ac.il).I. Cohen is with the Department of Electrical Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel (e-mail: icohen@ee.technion.ac.il). P. C. W. Sommen is with the Signal Processing

Integrated acoustic echo and background noise suppression technique based on soft decision

“…This is clearly different from the previous approach in [10] in that the method of [10] does not substantially estimate and include the background noise power because of the difficulty in estimating the noise power after the AES algorithm as explained in the first paragraph of Section 2. Specifically, the combined power l cb (i, k) is estimated by assuming that the acoustic echo and noise are uncorrelated and then combining the estimated echo and noise power based on the long-term smoothing scheme with a parameter a lcb such that whereλ e (i, k) is derived as in (8). Actually, notice that if E[|D(i,k)| 2 |Y(i,k)] ≅ 0, (11) becomes the original AES algorithm as in [10], while (11) results in the conventional NR algorithm in case thatλ e (i, k) is nearly zero.…”

“…But, an estimate of the variance of the echo signal was assumed to be known a priori, which inherently requires the AEC before the NR module. Other closely related technique by same authors is an approach of combined suppression of residual echo, reverberation, and background noise in a fashion of the post-filter following the traditional AEC [8]. But, the cancellation is performed directly on the waveform as in [7,8].…”

“…Other closely related technique by same authors is an approach of combined suppression of residual echo, reverberation, and background noise in a fashion of the post-filter following the traditional AEC [8]. But, the cancellation is performed directly on the waveform as in [7,8]. The algorithm is sensitive to the misalignment in the echo path response estimate.…”

Acoustic Echo Cancellation: Dual Architecture Implementation

“…A post filter, appended to the system, has been demonstrated to be an effective addition (Habbets, 2008;Gustafsson et al, 2002). Habets et al (2008) provides an excellent overview of post filters designed to mitigate the limitations of a deficient adaptive filter. The addition of a robust post filter has also been demonstrated to help alleviate adaptive algorithm computation complexity by allowing the filter to use a smaller filter order.…”

Application of combined temporal and spectral processing methods for speaker recognition under noisy, reverberant or multi-speaker environments

“…In case of reverberation, the reverberant speech can be divided into two parts namely early reverberation and late reverberation. Early reverberation tends to perceptually reinforce the direct sound and is therefore considered harmless to speech intelligibility, whereas the late ones are deleterious to speech quality and intelligibility (Habets et al 2008). In such case, spectral subtraction-based methods estimate the late reverberant spectral density and subtract it from the reverberant speech spectra to obtain the enhanced signal (Lebart & Boucher 2001;Habets et al 2008).…”