DSP based real time implementation of an advanced analysis tool for audio channels

A description is given of the noise-to-mask ratio (NMR) meter, a device used to measure the audibility of error signals according to the laws of psychoacoustics. The authors review the working principles of the NMR and describe its real-time implementation aspects. The application of the NMR to several source coding schemes is shown, and future developments in this area are discussed. It is concluded that NMR measurements currently cannot replace listening tests completely. What they can do is deliver objective, reproducible results that help to point out critical pieces of music as well as weak parts of algorithms. It is noted that even subtle changes in the audio channel under test will usually result in measurable differences even when listening tests are not applicable