Küch F (2005)
Publication Language: English
Publication Type: Thesis
Publication year: 2005
Publisher: University Erlangen-Nuremberg
In todays telecommunication devices often cheap audio hardware is included which introduces non-negligible nonlinear distortion into the loudspeaker signal. In case of hands-free telephone systems or mobile communication devices, these nonlinear audio components cause nonlinearly distorted acoustic echoes that can not be sufficiently attenuated by purely linear echo cancellers. This application exemplifies the growing demand for nonlinear adaptive signal processing methods. In this work, we address the task to provide nonlinear adaptive algorithms for applications in acoustic echo cancellation in order to overcome performance limitations of linear approaches. Based on a nonlinear discrete-time model for the acoustic echo path, we focus on special types of adaptive polynomial filters which require only little a priori knowledge about the audio hardware actually included in the telecommunication device. If moderately-sized loudspeakers represent the only source of nonlinear distortion, second-order Volterra filters can been used to model their frequency-dependent nonlinear behaviour. Additionally, we consider the case that only the amplifier or the miniaturized loudspeaker of a mobile phone causes the nonlinear distortion in the echo path. For this scenario, an orthogonalized version of adaptive power filters is proposed in order to improve the echo cancellation performance compared to purely linear approaches in case of saturation-type nonlinearities included in the echo path. Experimental results obtained for real loudspeaker systems are presented in order to verify the suitability of the discussed nonlinear adaptive algorithms for nonlinear acoustic echo cancellation.
Küch, F. (2005). Adaptive Polynomial Filters and their Application to Nonlinear Acoustic Echo Cancellation (Dissertation).
Küch, Fabian. Adaptive Polynomial Filters and their Application to Nonlinear Acoustic Echo Cancellation. Dissertation, Erlangen: University Erlangen-Nuremberg, 2005.