News 18-07 (No.367)
Issued : July 25, 2018
Yokohama Kyoritsu Gakuen’s New Worship Sanctuary
By Fumiaki Sakamaki
Yokohama Kyoritsu Gakuen (Doremus School) is a combined middle school and high school academic institution for girls with more than a 140-year history. Located in the Yamate district of Yokohama City, the campus’ main building was designed by architect William Vories in commemoration of the school’s 60th anniversary. This wood-frame structure continues to be used by the school today, some 87 years after its construction. The main school building has been registered with the city of Yokohama as a tangible cultural property because of its historical value.
During the many years that the school has continued to flourish, some of the school’s buildings increasingly exhibited wear and tear. Not long ago, the school decided to pursue a renewal plan for its campus. The plan calls for the school’s historical main building to be restored and preserved. Other campus buildings are being replaced one at a time with new structures. The renewal plan follows a schedule that maintains campus life unchanged during the construction period and enables the school to continue to hold all instruction and activities in permanent buildings without adding any temporary structures.
The project featured in this article is the first phase of the school’s redevelopment plan. It replaced the old south school building with a new south school building. One feature of the new building, a 1,200-seat sanctuary on the basement level, specifically replaces the 1,370-seat auditorium that the school previously used for worship services every morning.
The architectural firm Nihon Sekkei designed the new south school building and Hazama Ando Corporation served as the general contractor. Nagata Acoustics provided acoustical consulting services during the design and construction phases of the project. We also conducted acoustical measurement testing of the old south school building’s auditorium and of the completed new sanctuary in the new south school building.
Auditorium in the former south school building
New sanctuary (view from the audience side)
New sanctuary (view from the front wall)
At the start of the design phase of the project we measured the acoustical characteristics of the old south school building’s auditorium to obtain data for the new sanctuary’s room acoustics design. The auditorium had carpeted flooring and other elements that resulted in an excess of sound absorption and the reverberation time measured 1.0 seconds (at 500 Hz and with the space empty of people). We considered this reverberation time to be shorter than desired for a worship space. For the new sanctuary’s room acoustic design, we aimed to achieve a relatively long reverberation time appropriate to electric organ music and worship services.
The new sanctuary’s seating accommodates 1,200 students and teaching staffs on a single floor. Because the sanctuary’s location is on the basement level of the building, we could only achieve a ceiling height of 6 m. (20ft), which is not a generous height for a room of this purpose. To maximize every possible millimeter of height in the room, the interior design of the sanctuary leaves the concrete ceiling slab exposed without any additional ceiling material. For the surface treatment of the exposed concrete ceiling we specified a rough-textured finish to soften the sound reflections from that surface.
To obtain the desired long reverberation in the sanctuary, we specified that the interior surfaces have sound-reflecting finishes, except for a part of the rear wall where we specified with rock wool board which absorbs the sound. For the room’s fixed seating, we specified that the seats (but not the seat backs) be cushioned to lessen the difference between the reverberation time when the sanctuary is empty of people and when all seats are occupied.
We distributed indirect lighting and loudspeakers across the ceiling using a design that incorporates steel tracks of 1.6 mm. (0.06 in.) thickness installed so that they are not visible when seen from below. To prevent these metal tracks from producing any ringing or buzzing sounds we sprayed the rear sides of the tracks with a material that will prevent this kind of noise.
Ahlborn electric organ console
An Ahlborn electric organ used in the old south building’s auditorium has been relocated to the new sanctuary, including moving both its speakers and console. We installed the Ahlborn electric organ’s existing loudspeaker on the rear wall of the sanctuary and distributed additional, new speakers at the front lectern and at the ceiling equipment grid. With the support of the new, auxiliary speakers, the organ’s music can be heard throughout the sanctuary.
When the project completed, we measured the acoustics of the new sanctuary and obtained a reverberation time of 1.6 seconds (at 500 Hz, with the space empty of people). This result provides a significantly longer reverberation time compared with the auditorium that the sanctuary replaced. During the measuring process, we invited the organ music teacher to attend and play in the new sanctuary. The teacher confirmed the ease of playing the organ in the new space and also complimented us on the sanctuary’s acoustics.
The new Japanese school year began in April. I am glad that we were able to build a space where the students can enjoy their daily worship services and other activities with improved acoustics.
(Photographs courtesy of Susumu Koshimizu)
Nagata Acoustics Inc.
Hongo Segawa Bldg. 3F, 2-35-10 Hongo
Bunkyo-ku, Tokyo 113-0033, Japan
Tel: +81-3-5800-2671, Fax: +81-3-5800-2672
1990 S. Bundy Drive, Suite 795
Los Angeles, CA 90025
Tel: +1-310-231-7878, Fax: +1-310-231-7816
75, avenue Parmentier
Tel: +33 (0)1 40 21 44 25, Fax: +33 (0)1 40 21 24 00