A double-slip motion of a cello sound is investigated experimentally with a
bowing machine and analyzed using a Finite-Difference Time Domain (FDTD)
cochlear model. A double-slip sound is investigated. Here the sawtooth motion
of normal bowing is basically present, but within each period the bow hair
tears off the strings once more within the period, resulting in a blurred
sound. This additional intermediate slip appears around the middle of each
period and drifts temporally around while the sound progresses. When the
double-slip is perfectly in the middle of one period the sound is that of a
regular sawtooth motion. If not, two periodicities are present around double
the fundamental periodicity, making the sound arbitrary. Analyzing the sound
with a Wavelet-transform, the expected double-peak of two periodicities around
the second partial cannot be found. Analyzing the tone with a cochlear FDTD
model including the transfer of mechanical energy into spikes, the doubling and
even more complex behaviour is perfectly represented in the Interspike Interval
(ISI) of two adjacent spikes. This cochlear spike representation fits perfectly
to an amplitude peak detection algorithm, tracking the precise time point of
the double-slip within the fundamental period. Therefore the ear is able to
detect the double-slip motion right at the transition from the basilar membrane
motion into electrical spikes.Comment: 9 pages, 7 figure