The perception of spectrally shaped additive noise in speech

The spectrum of additive noise was systematically varied according to three variables: correspondance between the noise and speech spectrum (4 levels), equal weighting or weighting according to the width of the Articulation Index bands, SNR of the output signal (2 levels). All combinations of these 16 noise conditions were added to high quality speech sampled at 8kHz, and presented to listeners for judgment. Difference judgments were analyzed by a multidimensional scaling procedure to gain information about the number and nature of the important subjective variables. Overall quality ratings were obtained as a measure of the improvement in perceived quality due to the spectral shaping of the additive noise. Several objective measures were also tested for their sensitivity in predicting the overall quality ratings.