International Symposium on Performance Science
ISBN 978-2-9601378-0-4© The Author 2013, Published by the AEC
All rights reserved

Effects of musical experience on synchrony
judgment accuracy: Taking into consideration
its relation to cochlear delay
Eriko Aiba1,3, Minoru Tsuzaki2, Noriko Nagata2, and Seiji Nakagawa1
1 Health Research Institute, National Institute of Advanced

Industrial Science and Technology, Japan
2 Faculty of Music, Kyoto City University of Arts, Japan
3 School of Science and Technology, Kwansei Gakuin University, Japan

Musicians are sensitive to the synchrony of multiple tone onsets. However, even when several sounds have a simultaneous onset, their temporal relationship might not be preserved at the cochlear level because of“cochlear delays” in perception. The purpose of this study was to investigate whether cochlear delay significantly affects synchrony judgment accuracy and whether this phenomenon is dependent on musical experience. We conducted a psychoacoustic experiment to measure synchrony
judgment accuracy in professional pianists, amateur pianists, amateurinstrumental musicians (non-pianists), and non-musically trained people. Our experimental stimuli comprised three types of chirps, which allowed us to control for the amount of cochlear delay. We found that, regardless of the type of instrument, musicians had more accurate synchrony judgment. This may be due to the effect of careful listening, whichis required as part of musical training. However, asymmetric aspects of
temporal processing in the human auditory system were unaffected bymusical experience.
Keywords: musical experience; cochlear delay; auditory periphery; synchrony judgment; pianists

A change in onset asynchrony of musical notes of just a few milliseconds canresult in a significant difference in musical expression. Thus, it is importantfor musicians to be able to carefully discern the synchrony of tone onset.
However, even when the components of discrete sounds physically begin atexactly the same time, their temporal relation might not be preserved at the378

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cochlear level because of “cochlear delay” (e.g. Békésy and Wever 1960). The
stiffness of the cochlear basilar membrane gradually decreases from the basalside to the apical side (e.g. de Boer 1980). As a result, the higher componentsof an input wave excite the basal side, while the lower components excite theapical side. The vibration in the region of the cochlear membrane associatedwith the lowest frequency is thus delayed by about 10 ms relative to the vibration in the region associated with the highest-frequency (Uppenkamp etal. 2001).
In our previous research, we measured synchrony judgment accuracy using three types of chirps that elicit different amounts of cochlear delay: acompensated delay chirp, enhanced delay chirp, and intrinsic delay chirp(Aiba et al. 2008). We found that judgment accuracy was higher for the enhanced delay chirp, which evoked enhanced cochlear delay, than for the compensated delay chirp, which cancelled out the cochlear delay. This finding
indicated that the human auditory system may have an asymmetric aspect on
temporal information processing. We also found that the judgment accuracyof professional musicians was significantly higher than that of non-musicians(Aiba et al. 2011). In this case, most of the musicians were pianists, who areable to simultaneously control the timing of many different tones in order toplay their instrument. Therefore, we hypothesized that pianists in particularhave a greater ability to judge synchrony than other types of musicians.
The purposes of this study were (1) to investigate whether the amount ofcochlear delay has a significant effect on synchrony judgment accuracy and(2) to assess whether musical experience has an effect on synchrony judgment accuracy.
We conducted a psychoacoustic experiment to measure synchrony judgment accuracy in professional musicians, amateur musicians, and non-musicians. We used three different types of chirps to manipulate levels of cochlear
delay.
METHOD
Participants
Eight professional pianists (25.5±4.7 years of training), eight amateur pianists (17.4±7.2 years of training), five amateur musicians (non-pianists,6.6±4.5 years of training) and seven non-musically trained people (0.4±0.7years of training) with normal hearing and no history of hearing problems
participated in this study. All of the professional pianists had received at least
one prize in a domestic or foreign competition.

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Materials
We employed three types of sounds meant to induce different amounts ofcochlear delay: (1) compensated delay chirp, (2) enhanced delay chirp, and(3) intrinsic delay chirp (see Figure 1). In the compensated delay chirp, thefrequency was instantaneously increased to cancel out the cochlear delay. We
used a frequency pattern originally calculated by Dau et al. (2000), wherein
the frequency increases as a function of time. In the enhanced delay chirp, thetemporal function was opposite to that of the compensated delay chirp. In
these two chirps, the frequency either increased from 0.1 to 10.4 kHz or decreased from 10.4 to 0.1 kHz. The stimuli had tapered transients at both ends
with a raised cosine wave of 0.1 kHz. We also used an intrinsic delay chirp(pulse), which had no delay imposed on any frequency component. The intrinsic delay chirp was passed through a low-pass filter with a cut-off frequency of 10.4 kHz.
Procedure
We used a two-interval, two-alternative forced choice (2I2AFC) procedure
wherein participants were asked to detect synchronous pairs of stimuli. Twopairs of sounds were presented to the participant in each trial: one interval

Figure 1. The panels on the left show the waveforms of each chirp, and the panels on theright show the corresponding function of cochlear delay. The solid lines on the rightshow the frequency pattern as a function of time for each delay condition. The broken
line shows the time required for all frequencies to reach maximum amplitude at thebasilar membrane. (See full color version at www.performancescience.org.)

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contained a synchronous pair and the other interval contained an asynchronous pair. The asynchronous pairs had seven types of temporal asynchrony(0.2, 0.4, 1.0, 2.3, 5.1, 11.4, or 25.6 ms), spaced in a rough logarithmic pattern.
The order of presentation of the synchronous and asynchronous pairs wasrandomized across trials. The two pairs were separated by a 500–700 ms
inter-stimulus interval. The type of sound was consistent within each trial.
There were three sound-type conditions: (1) compensated delay, (2) enhanced delay, and (3) intrinsic delay. The total number of stimulus-type combinations was 72 (three sound-type conditions, twelve variations of temporal
asynchrony, and two patterns of synchronous pair order). The participants
repeated each combination 10 times, which brought the total number of trials
to 720. All factors (sound type, temporal asynchrony, and presentation order)
were randomized and executed as within-participant factors.
The participants were informed that each trial would have two intervals
containing two sounds, and that the two sounds would be synchronous in one
interval but asynchronous in the other interval. They were asked to choose
the interval containing the synchronous pair. Participants had as many
training trials as they felt they needed, and received feedback after eachjudgment. They were able to take breaks at any time.
Thresholds were estimated from the seven points on the psychometricfunction by fitting a sigmoid function on the data for each participant andcomputing the temporal asynchrony value corresponding to 75% correct responses.
RESULTS
The average estimated thresholds for each level of musical experience andeach sound type are shown in Figure 2. A two-way factorial fixed-effect
ANOVA was performed with music experience and sound type as the mainfactors. Music experience (F3,80=7.14, p<0.01) and sound type (F2,80=21.7,p<0.01) were both significant as main factors.
The accuracy of synchrony judgment was highest among the group of
professional pianists. We found no interaction between level of music experience and sound type. We used the Tukey-Kramer HSD test to investigate detailed differences in sound type and music experience, respectively. We founda significant difference between professional pianists and amateur pianists
and non-musically trained individuals in terms of judgment accuracy. Additionally, we found no significant differences in judgment accuracy between
amateur musicians (non-pianists) and amateur pianists. There were significant differences in judgment accuracy among all three sound types.

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Figure 1. The average estimated thresholds and SDs in ms for each level of music experience and sound type. The arms at the side of the graph legend indicate the participantgroups that showed significant differences (*p<0.05).

DISCUSSION
We found the judgment accuracy of professional pianists and non-musicallytrained individuals to be the highest and the lowest of the participant groups,respectively. However, we found no significant differences between amateur
musicians (non-pianists) and amateur pianists in terms of judgment accuracy. Our results indicate that, regardless of the type of instrument a musicianplays, careful attention regarding the synchrony of tone onset is important formusical performance. It is possible that, as musicians work to improve theirinstrumental performance, the accuracy of their synchrony judgment increases.
With regard to sound type, the synchrony judgment accuracy of individuals with all types of music experience decreased in the following order: compensated delay, enhanced delay, and intrinsic delay condition. This suggeststhat asymmetric aspects of temporal processing in the human auditory system do not change with music experience. In all types of music experience,
the auditory system appeared less sensitive to this delay following the intrinsic, natural direction; that is, cochlear delays. There is the possibility that theimprovement of synchrony judgment accuracy of musicians occurred in theupper levels of cochlear range.
In our future research, we plan to compare the onset judgment of professional pianists, who work more with sounds that have a sudden attack, withthat of violinists, who work with sounds that often have a gradual onset.

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Acknowledgments
This work was supported by Grant-in-Aid for the JSPS Fellows No.24-10633, Grant-inAid for Scientific Research (A) No. 24243070, and the JSPS through the NEXT Program, initiated by the CSTP.
Address for correspondence
Eriko Aiba, Health Research Institute, National Institute of Advanced Industrial Scienceand Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan; Email: aiba.
eriko@aist.go.jp
References
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relation to the auditory brainstem response: the difference between pianists andnon-pianists. Journal of Advanced Computational Intelligence and Intelligent Informatics, 15, pp. 962-971.
Aiba E., Tsuzaki M., Tanaka S., and Unoki M. (2008). Judgment of perceptual synchrony between two pulses and verification of its relation to cochlear delay by anauditory model. Japanese Psychological Research, 50, pp. 204-213.
Békésy G. V. and Wever E. G. (1960). Experiments in Hearing. New York: McGraw-Hill
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de Boer E. (1980). Auditory physics. Physical principles in hearing theory. I. Physics
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Dau T., Wegner O., Mellert V., and Kollmeier B. (2000). Auditory brainstem responses
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Uppenkamp S., Fobel S., and Patterson R. D. (2001). The effects of temporal asymmetryon the detection and perception of short chirps. Hearing Research, 158, pp. 71-83.