An MDCT-domain audio denoising method with a block switching scheme

In this paper, an audio denoising method is proposed for improving the quality of handheld audio recording devices. The proposed method reduces noise differently depending on the block size in the modified discrete cosine transform (MDCT) analysis of an audio coder. Specifically, denoising for a long block is performed by multi-band spectral subtraction (MBSS) with perceptually weighted scalefactor bands, while that for a short block is performed by subband power scaling to maintain coherence of power with the previously-denoised long block. In order to evaluate the performance of the proposed method, it is first embedded into MPEG-2 advanced audio coding (AAC) that is popularly used for audio recording devices. Then, its performance is compared with that of a conventional audio denoising method based on block thresholding in terms of cepstral distortion, subjective quality, and computational complexity. It is shown from performance comparison that the proposed method outperforms the block thresholding method in both objective and subjective measurements. Moreover, the complexity of the proposed method is sufficiently lowered to be implemented on most resource-constrained handheld audio recording devices, unlike the conventional method.