The effect of fundamental frequency on the brightness dimension of timbre

The dependency of the brightness dimension of timbre on fundamental frequency (F0) was examined experimentally. Subjects compared the timbres of 24 synthetic stimuli, produced by the combination of six values of spectral centroid to obtain different values of expected brightness, and four F0's, ranging over 18 semitones. Subjects were instructed to ignore pitch differences. Dissimilarity scores were analyzed by both ANOVA and multidimensional scaling (MDS). Results show that timbres can be compared between stimuli with different F0's over the range tested, and that differences in F0 affect timbre dissimilarity in two ways. First, dissimilarity scores reveal a term proportional to F0 difference that shows up in the MDS solution as a dimension correlated with F0 and orthogonal to other timbre dimensions. Second, F0 affects systematically the timbre dimension (brightness) correlated with spectral centroid. Interestingly, both terms covaried with differences in F0 rather than chroma or consonance. The first term probably corresponds to pitch. The second can be eliminated if the formula for spectral centroid is modified by introducing a corrective factor dependent on F0. (c) 2007 Acoustical Society of America.