EC Types & Applications \tAcoustic Echo Canceller A discussion of how an Acoustic Echo Canceller can remove audible echoes caused by acoustic coupling and acoustic reverberation \tLine/Network Echo Canceller A discussion of how line/network cancellers can remove audible echoes caused by telephone hybrid circuits \tLine and Acoustic Echo Canceller Combined A discussion of echo cancellers that handle both line echo and acoustic echo \tFar-end Echo Canceller A discussion of how an Acoustic Echo Canceller can remove audible echoes received from the far-end speaker \tStereo Acoustic Echo Canceller A discussion of acoustic echo cancellers used with audio conferencing and surround sound systems \tAcoustic Echo Cancellation (AEC) for Commercially Available Off-the-Shelf (COTS) Hardware A discussion of acoustic echo cancellation solutions for use with COTS hardware. \tNon-conventional Applications of Acoustic Echo Cancellation (AEC) Acoustic echo cancellation can be applied to any voice communication system to achieve high quality full-duplex conversations. \tStereophonic Acoustic Echo Cancellation A discussion of stereophonic acoustic echo cancellation \tWideband Acoustic Echo Cancellation A discussion of acoustic echo cancellation (AEC) used in wideband audio teleconferencing where the presence of the acoustic echoes in the microphone signal cause significant degradation in the quality of conversation. \tSubband Acoustic Echo Cancellation Subband adaptive filtering overcomes many of the limitations of traditional time-domain normalized least means squares implementations of echo cancellation. \tVoIP Echo Cancellation A discussion of echo cancellation in VoIP networks \tEcho Cancellation Software in VoIP Gateways A discussion of handling echoes generated in the transmission path. \tEcho Cancellation in Cellular Networks There are several cellular network architectures which influence the implementation of an echo canceller. \tFrequency Domain Adaptive Filtering in Echo Cancellation Frequency Domain Adaptive Filters (FDAF) in acoustic echo cancellation applications provide several advantages over its time domain counterpart. \tTandem Echo Cancellers Discussion of echo cancellers connected in tandem used in networking and voice enhancement. \tAcoustic Echo Cancellation with Expanded Dynamic Range Discussion of echo cancellers with extended dynamic range Adaptive Filters \tFIR Filter Design Discussion of FIR filter design using suboptimal and optimal methods \tHigh-Pass Filters in Echo Cancellers Discussion of high-pass filters used in echo cancellation to achieve expected product performance. \tEcho Cancellation based on Adaptive IIR Filtering Discussion of the advantages of adaptive IIR filtering used in echo cancellation. \tLine Echo Canceller with Backup FIR Filter Discussion on using a second FIR filter with the FIR adaptive filter in applications where the echo path is relatively constant. \tLinear Phase Filters in Acoustic Echo Cancellation A discussion of linear phase filters used in acoustic echo cancellation. \tAcoustic Echo Cancellation for Sparse Echo Paths How the Proportionate NLMS algorithm can be used to process sparse echo paths in acoustic echo cancellation. \tVariable Tap Length Filters for Acoustic Echo Cancellation A discussion of managing conflicting requirements of fast convergence and full echo cancellation. \tTwo-Path Method for Acoustic Echo Cancellation Discussion on AEC using a two-path method to mitigate the acoustic coupling between the loudspeaker and microphone for achieving full-duplex communication in audio conferencing systems. \tParticle Swarm Optimization in the Design of Adaptive FIR Filters Particle Swarm Optimization in the Design of Adaptive FIR Filters. \tParticle Swarm Optimization in the Design of Adaptive IIR Filters Particle Swarm Optimization in the Design of Adaptive IIR Filters. \tKalman Filter in Acoustic Echo Cancellation A discussion of Kalman filters used in acoustic echo cancellation \tGammachirp Filter for Acoustic Echo Cancellation A discussion of Gammachirp filters used in acoustic echo cancellation \tHaar Wavelet Decomposition in Acoustic Echo Cancellation A discussion of multi-resolution analysis in acoustic echo cancellation \tViterbi Algorithm in Speech Enhancement and HMM Discussion on applications of the Viterbi algorithm to speech enhancement and other technologies \tVolterra AEC A discussion of non-linear aspects of the echo path and representation using a Volterra series. \tCritically Sampled Uniform Sub-Band Echo Cancellation using LMS-type Algorithms A discussion of subband sampling methods with LMS algorithms. \tOctave Banks for Acoustic Filtering A discussion on the use of octave banks with acoustic filters \tAcoustic Echo Cancellation (AEC) for Sparse Echo Paths Method for capturing essential information from a sparse echo path while leaving other information for echo suppression in an acoustic echo cancellation system. \tSparse Echo Cancellers A discussion of handling echo path impulse responses that are relatively short with sparsely distributed clusters of high energy EC Features & Filter Control \tComfort Noise Generation in Echo Cancellers A discussion of CNG functionality used with echo cancellation to improve the far-end listener experience \tDouble-Talk Detection in Echo Cancellation The presence of the near-end talker during far-end speech is a source of disruption in the adaptation of the filter. Adaptation of the filter must be prevented via a double-talk detector. \tTone Detectors in Echo Cancellers Discussion on how harmonic excitation can impact convergence of the echo canceller adaptive filter. \tLine Echo Canceller with Bulk Delay Compensation Bulk delay compensation can be used for access network configurations with signal delays between the line echo canceller and hybrid circuit ports. \tHidden Markov Models in Acoustic Echo Cancellation A discussion of hidden Markov models used in acoustic echo cancellation \tSignal De-Correlation Discussion of advantages of signal de-correlation in different applications \tCross-Correlations in Echo Cancellation The cross-correlation between various signal components can be revealing to the state of the echo canceller. \tStability Control by Echo Canceller Discussion of echo canceller’s adaptive filtering and stability control in the open and closed loop systems \tPotential Instability of NE/FE System with Echo Cancellation Discussion on stability analysis of Near-End/Far-End systems with echo cancellation \tPotential Instability of NE/FE System without Echo Cancellation Discussion on stability analysis of Near-End/Far-End systems without echo cancellation \tAdaptive Filter Algorithm Stability Discussion on controlling adaptive filter algorithm stability during initial adaptation. \tNonlinear Acoustic Echo Cancellation A discussion of non-linear acoustic echo canceller design \tThe Combined Reduction of Echo and Noise Tackling noise reduction and residual echo reduction in a joint effort. \tPost Filtering for Residual Echo Control Post filtering of echo cancellation systems is important for environments with large levels of non-linear distortion. \tVariable Step-size and Regularization Parameters for NLMS In echo cancellation, proper control of step-size and regularization parameters of the NLMS can improve the overall performance of the system. \tFrequency Offset Compensation in Echo Cancellation Frequency offset in echo cancellation refers to when the sampling frequency of the far-end and near-end signals are not the same. \tAligning Audio Streams Captured using Unsynchronized Clocks When using multiple data collection devices that are not driven by the same master clock, audio streams must be aligned for testing audio algorithms. \tDynamic Time Warping Aligning two sequences of feature vectors by warping the time axis \tPsychoacoustic Echo Cancellation Understanding perception of echo can improve acoustic echo cancellation. \tEcho Control on Codec Parameters Direct modification of codec parameters provides a low complexity solution to voice quality enhancement in cellular networks. \tStatistical Joint Control of Acoustic Echo Canceller and Post-Filter Based on statistical properties of the adaptive filter, the echo canceller step-size and the post-filter can be controlled jointly. Challenges of EC \tNon-Linear AEC Discussion of acoustic echo path non-linearities limiting AEC performance \tHandling of Nonlinearities in Echo Cancellation A discussion on how an adaptive filter reacts to non-linear distortions. \tThe Challenges of Stereophonic\\Multichannel Echo Cancellation's As in all acoustic hands-free communications systems, acoustic echo cancellation is a requirement. Multichannel echo cancellation provides an additional set of signal processing challenges as compared to monophonic echo cancellation. \tAcoustic Echo Paths Characteristics and AEC A discussion of AEC handling of acoustic echo path delays, early reflections and late reflections, echoes related to non-linear distortions. \tEcho in Voice over IP Networks Discussion of reasons to deploy echo cancellers in VoIP networks contrasted with their use in PSTN. \tPerception of Echo How round trip delay and bandwidth influence the perception of echoes. \tCritical Distance A discussion of critical distance for positioning loudspeakers and microphones when designing a sound or a control room. \tCritical Distance and RT60 Discussion of method for estimating critical distance for room reverberation \tControlling RT60 – Practical Notes Discussion of controlling RT60 when evaluating speech enhancement devices \tEcho Cancellation with Dereverberation A discussion of the effect of dereverberation processing combined with echo cancellation. \tEcho Cancellation in IP Networks The implementation of Voice over IP (VoIP) networks, presents a new set of challenges in optimizing the voice quality and providing the expected toll quality. \tThe Affect of Convergence Speed in the Two-Path Method The Affect of Convergence Speed in the Two-Path Method. \tFixed Point Mathematics for Acoustic Echo Cancellation How fixed point mathematics can improve acoustic echo cancellation performance \tBasic Linear Algebra Subprograms (BLAS) in C Examples of dot product, matrix multiplication, and matrix matrix multiplication using CBLAS Library Estimation \tMethods of RT60 Estimation A discussion of methods to estimate RT60 to characterize room reverberation effects. \tPractice of RT60 Estimation in Bands Discussion of methods to estimate room reverberation in subbands \tEstimating Echo Return Loss and Echo Return Loss Enhancement To achieve an ubiquitous solution for an acoustic echo cancellation system, an adaptive filter control system for the echo canceller and the post-filter is required. \tEstimating ERL from AF FIR Taps Method for estimating the ERL value of the echo path using the adaptive filter FIR taps. \tRoom Impulse Response A discussion on estimating the room impulse response, i.e. the transfer function between the sound source and microphone. \tImpulse Response Estimation for Audio via Complementary Sequences Use of complementary sequences for impulse response estimation of audio devices and acoustic systems to minimize adverse effects of background noise. \tA and C Weighting via Bilinear Transform Discussion on the standard weighting curves for unbiased digital filtering using bilinear transformation Testing \tG.168 Test Methodology Discussion of details pertaining to LEC/NEC testing methodology \tG.168 Defined Echo Path Models A discussion of evaluating any line/network echo canceller when using a laboratory setup \tEnergy and Level Estimation for G.168 Testing Methods of signal energy/level estimation for G.168 compliance testing. \tLine and Acoustic Echo Diagnostics Diagnosing and debugging methods to determine what contributes most to the presence of echo for a given system configuration and acoustic scenario. \tEqualization For ETSI-Compliant Audio Facility Discussion for setup of an audio testing facility for acoustical evaluation of audio designs and products \tETSI Audio Room Equalization – Selected Details Discussion on frequency band selection and the equalization process used for audio facility setup. \tMinimum Phase LTI Systems in Context of Equalization A discussion of how a direct-inverse method can be used to equalize minimum phase LTI systems. \tEcho Path Delay Identification Offline Method to independently estimate the echo path delay with high degree of confidence. \tLevel Measurements via ITU P56 and Weightingg Discussion of practices for measuring audio signals \tEcho Paths for Hands-Free Terminals Discussion on ITU P.340 and modeling echo paths for hands free terminals. EC & Noise Reduction \tRobust Adaptive Algorithms for Echo Cancellation An acoustic echo canceller may need to address different acoustic and noise control environment issues. Constraints include the volume of the enclosure, the required bandwidth, and the tolerable delay. \tForensic Speaker Recognition Preprocessor Discussion on using speech preprocessing to improve speech recognition rates in ASR and other applications. \tThe Combination of Adaptive Filters An acoustic echo canceller may need to address different acoustic and noise control environment issues. Constraints include the volume of the enclosure, the required bandwidth, and the tolerable delay. \tComb Filtering in Acoustics A discussion of the comb filtering effect, caused by the position of a loudspeaker, that can impact the listener’s experience. \tMore on Observations Regarding Musical Noise Discussion of musical noise and its characteristics \tSynthetic Noise for Voice Enhancement Discussion of synthetic random noise signals used in Voice Enhancement during development, verification and testing \tSynthetic Noise of Predefined Spectrum for Voice Enhancement Methods for generating random noise signals with a predefined spectrum for Voice Enhancement \tBlind Source Separation for Noise Reduction in Mobile Blind Source Separation or Independent Component Analysis is a multi-channel technique that can be used for noise reduction/cancellation in Mobile Telecommunications, such as cell phones and tablets Speech Dereverberation \tSpeech Dereverberation using Channel Inversion and Equalization A discussion of channel inversion and equalization techniques used to dereverberate speech. \tDereverberation using Spectral Subtraction A discussion on methods to remove reverberation from received speech signals \tVoice Activity Detection for Dereverberation A discussion of using VAD to estimate the speech reverberation time. \tCombination of Dereverberation and Adaptive Beamforming A discussion on combining dereverberation and beamforming algorithms. \tVarious Models of Room Reverberation A discussion of different room models used for speech enhancement device evaluation during development \tReverberation Cancellation Versus Suppression A discussion of different techniques for handling reverberation.