Simulation of Reconstruction of Oversampled Signales in Digital Loudspeakers
The technique of oversampling and noise shaping has the potential to improve the resolution of digital loudspeaker systems, at the expense of increasing the signal bandwidth. Previous work has shown that the acoustic radiator in a digital loudspeaker system can act as a reconstruction filter if the oversampled signal bandwidth exceeds the transducer bandwidth. If the oversampled signal is within the transducer bandwidth, the use of reconstruction filters has to be considered in the system. This paper presents an investigation of reconstruction with both pre-acoustic and post-acoustic filtering. Mathematical modelling suggests that the reconstruction in a direct digital-to-analogue loudspeaker should take place before the summation of the digital bitstreams to avoid intermodulation distortion. This is counter-intuitive because the electronic driving signals are no longer digital in the digital loudspeaker system.
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