A comparison of different loudspeaker models to empirically estimated non-linearities

This paper investigates and questions the suitability of modelling non-linear loudspeaker distortion with scalar diagonal (SD) Volterra series. This approach, popular in studies of non-linear acoustic echo cancellation (NAEC), is compared to an alternative non-scalar diagonal (NSD) model. The new model is estimated empirically but based on the theoretical underpinnings of non-linear convolution. Using common, real-speech test signals, the loudspeaker outputs synthesised by each model are evaluated objectively through their comparison to real loudspeaker outputs measured in controlled conditions. Results show that non-linear distortion estimated with the NSD model better reflects that measured empirically. We also show that NAEC experiments conducted with SD loudspeaker models have the potential to over-exaggerate performance, whereas those conducted with an NSD model better reflect practical performance.