Comodulation masking release in bit-rate reduction systems

Martin D. Vestergaard, Karsten Bo Rasmussen, Torben Poulsen

    Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

    Abstract

    It has been suggested that the level dependence of the upper masking slopebe utilised in perceptual models in bit-rate reduction systems. However,comodulation masking release (CMR) phenomena lead to a reduction of themasking effect when a masker and a probe signal are amplitude modulated withthe same frequency. In bit-rate reduction systems the masker would be theaudio signal and the probe signal would represent the quantization noise.Masking curves have been determined for sinusoids and 1-Bark-wide noisemaskers in order to investigate the risk of CMR, when quantizing depths arefixed in accordance with psycho-acoustical principles. Masker frequencies of500Hz, 1kHz and 2kHz have been investigated, and the masking of pure toneprobes has been determined in the first four 1/3 octaves above the masker.Modulation frequencies between 6Hz and 20Hz were used with a modulationdepth of 0.75. CMR of up to 10dB was obtained at a distance of 6 Bark abovethe masker. The amount of CMR was found to depend on the presentation levelof the masker; a higher masker level leads to a higher CMR-effect. Hence,the risk of CMR affecting the subjective performance of bit-rate reductionsystems cannot be ruled out.

    Original languageEnglish
    Title of host publicationActa Acustica Supplement 1 : Collected Papers
    Number of pages4
    PublisherS. Hirzel
    Publication date1999
    Publication statusPublished - 1999
    Event137th Regular Meeting of the Acoustical Society of America, 2nd Convention of the European Acoustics Association - Technical University of Berlin, Berlin, Germany
    Duration: 15 Mar 199919 Mar 1999

    Conference

    Conference137th Regular Meeting of the Acoustical Society of America, 2nd Convention of the European Acoustics Association
    LocationTechnical University of Berlin
    CountryGermany
    CityBerlin
    Period15/03/199919/03/1999

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