TY - JOUR
T1 - Seeing the sound of castanets
T2 - Acoustic resonances between shells captured by high-speed optical visualization with 1-mm resolution
AU - Ishikawa, Kenji
AU - Yatabe, Kohei
AU - Oikawa, Yasuhiro
N1 - Funding Information:
This work was supported in part by the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for JSPS Research Fellow (16J06772) and in part by the Waseda Research Institute for Science and Engineering, Grant-in-Aid for Young Scientists (Early Bird).
Publisher Copyright:
© 2020 Author(s).
PY - 2020/11/1
Y1 - 2020/11/1
N2 - Sound fields radiated from the castanet, a Spanish percussive instrument comprising two shells, were optically visualized. A measurement system, which used parallel phase-shifting interferometry and a high-speed polarization camera, enabled the capture of instantaneous sound fields around the castanets, while the castanets were played, with the spatial resolution of 1.1 mm and frame rate of 100 000 fps. By carefully aligning the tilt of the castanets, the sound fields within the 1-mm gaps between both the shells were captured. From the visualization results, two acoustic resonances between the shells were identified. The first mode appeared between 1000 and 2000 Hz and exhibited a frequency chirp of several hundred hertz for several milliseconds after the impact. This can be explained by the Helmholtz resonance with a time-varying resonator shape, which is caused by the movement of the shells after impact. The second mode showed a resonance pattern with a single nodal diameter at the center of the shells, i.e., the standing wave mode caused by the interior volume. These physical phenomena involved in the sound radiation were identified owing to the unique features of the optical imaging method, such as contactless nature and millimeter-resolution imaging of instantaneous pressure fields.
AB - Sound fields radiated from the castanet, a Spanish percussive instrument comprising two shells, were optically visualized. A measurement system, which used parallel phase-shifting interferometry and a high-speed polarization camera, enabled the capture of instantaneous sound fields around the castanets, while the castanets were played, with the spatial resolution of 1.1 mm and frame rate of 100 000 fps. By carefully aligning the tilt of the castanets, the sound fields within the 1-mm gaps between both the shells were captured. From the visualization results, two acoustic resonances between the shells were identified. The first mode appeared between 1000 and 2000 Hz and exhibited a frequency chirp of several hundred hertz for several milliseconds after the impact. This can be explained by the Helmholtz resonance with a time-varying resonator shape, which is caused by the movement of the shells after impact. The second mode showed a resonance pattern with a single nodal diameter at the center of the shells, i.e., the standing wave mode caused by the interior volume. These physical phenomena involved in the sound radiation were identified owing to the unique features of the optical imaging method, such as contactless nature and millimeter-resolution imaging of instantaneous pressure fields.
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U2 - 10.1121/10.0002446
DO - 10.1121/10.0002446
M3 - Article
C2 - 33261402
AN - SCOPUS:85097036402
SN - 0001-4966
VL - 148
SP - 3171
EP - 3180
JO - Journal of the Acoustical Society of America
JF - Journal of the Acoustical Society of America
IS - 5
ER -