In sound mixtures of more than one musical source, different vibrato patterns act as a cue that multiple sources are present for both human listeners and source separation algorithms. Matching the vibrato patterns of the signals in the mixture reduces the perception of multiple sources, particularly when the sources play in unison. This work introduces the vibrato matching algorithm, which first suppresses vibrato in a target signal and then transfers vibrato from a source signal to the target. An existing vibrato suppression algorithm is combined with a new algorithm for vibrato transfer, which imparts frequency modulation and amplitude modulation to the harmonics of the target signal, and amplitude modulation onto the spectral envelope of the non-harmonic residual component. Examples demonstrate the algorithm's utility as a vibrato control mechanism and as a tool for blending sound sources. Matching vibrato degrades the performance of source separation algorithms, suggesting a similar degradation in listeners ability to detect the presence of multiple sources.
Figures & tables
Figure 1: Signal flow for the vibrato matching algorithm. A target signal t(n) has its original vibrato suppressed and is then modulated using AM and FM patterns from a vibrato source signal s(n) .
Figure 2: Deriving an AM envelope from an RMS envelope.
Figure 3: Spectrograms of a vocal with vibrato (left), a vocal with different vibrato (middle), and the left signal after its vibrato was suppressed and vibrato from the middle signal was transferred onto it (right).
Figure 4: Spectrograms of a saxophone with vibrato (left), a violin with vibrato (middle), and the saxophone after its vibrato was suppressed and vibrato from the violin was transferred onto it (right).
Figure 5: Spectrograms of two vocal signals in unison, before and after matching vibrato patterns.
Figure 6: Spectrograms of a vocal signal and a flute signal separated by a perfect fifth, before and after matching vibrato patterns.
Figure 7: Unison source separation on a mixture of two vocal signals, before and after matching vibrato patterns.
Figure 8: Unison source separation on a mixture of bass oboe and bassoon, before and after matching vibrato patterns.