Loudspeaker Equalization with Post-Processing
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Loudspeaker Equalization with Post-Processing Wee Ser Center for Signal Processing, School of Electrical & Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore Email: [email protected]
Peng Wang Center for Signal Processing, School of Electrical & Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore Email: [email protected]
Ming Zhang Center for Signal Processing, School of Electrical & Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore Email: [email protected] Received 1 November 2001 and in revised form 23 June 2002 Loudspeaker equalization is an essential technique in audio system design. A well-known equalization scheme is based on the deconvolution of the desired equalized response with the measured impulse response of the loudspeaker. In this paper, a postprocessing scheme is combined with the deconvolution-based algorithm to provide a better equalization effect. Computer simulation results are given to demonstrate the significant improvement that can be achieved using this method. Keywords and phrases: loudspeaker equalizer, post-processing.
1. INTRODUCTION A loudspeaker is a device that converts a signal from its electric form to audible sound wave. Noticeable distortions may be introduced in this conversion leading to a significant loss of sound quality. The technique of loudspeaker equalization has thus been developed to deal with this problem. Among all the equalization schemes presented in the literature [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13], the deconvolutionbased scheme [1] has the simplest filter structure and is widely used. However, this scheme does not work effectively at low and middle frequencies. Multiband approach overcomes this shortcoming and is able to provide satisfactory equalization for the entire frequency band of interest [2, 3], but its complex structure prevents it from being used in low-cost systems. In our previous work reported in [4, 5], a warped filter has been incorporated into the multiband equalizer design to reduce the structural complexity. In this paper, a different design approach is investigated. By suitably combining the deconvolution-based equalizer with a postprocessing technique, a better equalization effect can be obtained with a marginal increase in the structural complexity. This paper is organized as follows. In Section 2, the deconvolution-based equalization scheme is briefly described and the principle of the proposed equalization
scheme with post-processing is introduced. In Section 3, the optimization process for the proposed scheme is discussed. Computer simulations have been conducted to demonstrate the effectiveness of the proposed scheme, and the results are given in Section 4. The paper ends with the concluding remarks of Section 5. 2.
PRINCIPLE OF THE PROPOSED SCHEME
Loudspeaker equalization involves the inverse filtering of the signal that is distorted by the loudspeaker. In the simplest case, it can be depicted as a convolution process, that is,
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