Due to recently changes in Japanese seismic standards, the modification of existing ceiling structures in large spaces (e.g. gymnasiums) for the prevention of possible falls have become one of the primary targets.
In most of the cases, the removal of the sound absorbing suspended ceiling for the seismic retrofitting affects directly to the acoustic characteristics of the space, creating the increase of the reverberation time and the appearing of the unpleasant flutter echo (e.g. specially when ball-bouncing a basketball ball in gymnasiums).
In this study, spaces (30x35x15 m) with different ceiling shapes have been acoustically simulated to better understand the issues that YAB Corporation has to face when quality acoustic conditions become an added priority during their renovation.
Impulse responses and ray tracing simulations show a significant flutter echo in the space with dome shape ceiling that can remind the existing flutter echo of the “whining dragon” of Toshogu shrine in Nikko.
Here, an interesting report about the whining dragon of Toshogu shrine "The Fluttering Echoes or Whining Dragon" by Sumio Yoshizawa. Published in the ICPE2006 (The International Conference of Engineering Physics 2006 in Tokyo).
Ray tracing simulation:
1DOME1
1DOME2
2CURVED1
3SLANTED1
4FLAT1
Auralizations:
Dry source: Recitation of Kazuhisa Takahashi 無響室録音：朗読 高橋和久
Impulse Responses