Bark Spectral Distortion (BSD)

BSD was developed at the University of California [145]. It was essentially the first objective measure to incorporate psychoacoustic responses. Its performance was quite good for speech coding distortions as compared to traditional objective measures (in time domain and in spectral domain). The BSD measure is based on the assumption that speech quality is directly related to speech loudness, which is a psychoacoustical term defined as the magnitude of auditory sensation. In order to calculate loudness, the speech signal is processed using the results of psychoacoustics measurements. BSD estimates the overall distortion by using the average Euclidean distance between loudness vectors of the reference and of the distorted speech. BSD works well in cases where the distortion in voiced regions represents the overall distortion, because it processes voiced regions only; for this reason, voiced regions must be detected.