Pitch center of stringed instrument vibrato tones.

The determination of the pitch center of frequency modulated sounds has been the focus of a number of previous studies. The sources have usually been pure tones or synthetic complex sounds with a well-defined spectral composition. These synthetic sounds differ in temporal and spectral properties from the sounds produced by musical instruments; and it is these acoustic sounds which performers are trained to produce and to perceive in order to make intonation choices. Thus samples chosen for this study consist of approximately 1 s of acoustic sounds produced by a virtuoso violist playing the notes D4, C5#, A5, and G6 with and without vibrato. The sounds without vibrato were then resampled to give frequencies from -15 to +21 cents with respect to the mean of the sound with vibrato. Two-interval two-alternative forced choice (212AFC) experiments were carried out comparing the sounds with vibrato to those without vibrato using two sets of musically experienced listeners as subjects. A control set consisting of the comparison of pitch levels of the unmodulated sounds was carried out simultaneously. Results are consistent with the finding that the pitch perceived is that of the mean. The difference limen inferred from the control set was 2.8 cents for the first group and 2.5 cents for the second group with an upper bound on the error of 1 cent.