2017/05/17

Restoration of the acoustic characteristics of Tsurukawa Playhouse in Kawagoe: (I) Application of 3D laser scan data to acoustic simulation

以下、今年の9月の建築学会大会にて発表予定の論文を英語で説明したものです。

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AIJ 2017 Title

RESTORATION OF THE ACOUSTIC CHARACTERISTICS OF TSURUKAWA PLAYHOUSE IN KAWAGOE: (I) APPLICATION OF 3D LASER SCAN DATA TO ACOUSTIC SIMULATION

Authors:
Antonio Sanchez-Parejo  (YAB Corporation)
Yu Morishita ( Institute of Industrial Science, The University of Tokyo )
Mitsuru Yabushita (YAB Corporation)
Clemens Büttner (Audio Communication Group, Institute of Technology Berlin)

Tsurukawa playhouse is located in Kawagoe city in the central Kanto region of Japan. The wooden building built in 1907 is presumed to be the only playhouse remaining in the metropolitan area. The wooden wheels embedded in the circular stage still remain, as well as the brick passage under the “hanamichi” (the walkway that extends from the stage to the audience seats) that connects the “naraku” (area under the stage) with the “toyaguchi” (the entrance connected at the back of the audience seats, used for actors). During Taisho era, the playhouse was used to entertain with the screening of photographs after World War I and later, and until 2000, it became a movie theatre.

The necessity of its restoration and reuse, has provided us with the opportunity to apply for the first time measuring methods with 3D laser scanning for the study of the acoustic characteristics of a historical space such as this one.

Exterior view of Tsurukawa playhouse in Taisho era

3D laser scanner 
The purpose of 3D laser scanning is to create point clouds (three dimensional positions) of geometric spaces. For most situations, a single scan will not produce a complete model of the building. For Tsurukawa playhouse multiple scans, as shown in the picture below, were required to obtain information about all surfaces of the building.
3D laser scan and acoustic measurement position

3D point cloud data 
 Although different software for the conversion of point cloud into 3D CAD can be used, the big size of scan files (13.6 GB in case of Tsurukawa playhouse) and the lack of precision that requires manual fixes, made most of this software very inefficient. In our case, the use of section slices from 3D scan data was selected, a simpler and less time-consuming method for the acquisition of geometry for the room acoustic simulation. This method allowed an exact representation of the historical room which allowed capturing the damaged ceiling of Tsurukawa playhouse, helping to improve the effectivity and performance of the acoustic restoration. Moreover, the damaged ceiling of Tsurugawaza was captured by the 3D scan, helping to increase the effectivity of the acoustic restoration.


3D scan point cloud sections of Tsurukawa playhouse

AutoCAD geometry from section slices

Geometry imported in CATT Acoustic software for acoustic simulation.

Results obtained from acoustic simulations were compared with current acoustic characteristics. Both impulse response of measurements and CATT Acoustic simulation results had similar waveforms. Showing similar shape, RASTI values between 0.53 to 0.60 (Fair) obtained in CATT simulation were lower than the ones obtained in actual measurements ranging from 0.58 to 0.70 (Fair /Good), background noise settings on the simulation could have affected the achievement of the values for the simulation. The room behaved as a non-mixing geometry/shape in the simulation (standing waves due to parallel walls reflection), so the reverberation time became a bit longer for CATT simulation (1.54s) than Eyring (CATT simulation) and actual measurements results, in both cases, was 0.9s.
Impulse responses. Actual measurement, CATT-Acoustic simulation

RASTI



Time Trace video simulation


Special thanks to Kawagoe Kura No Kai and Wooden Playhouses Study Group. 

測定に際し、川越蔵の会および木造劇場研究会の皆様にご協力をいただきました。記して感謝いたします。