News 14-04 (No.316)
Issued : April 25, 2014
[ Japanese Version ]
Stage Acoustics in Concert Halls: My Experience with Danish Radio Concert Hall
By Dr. Yasuhisa Toyota
Danish Radio Concert Hall
January 20, 2014 marked the 5th anniversary of the opening of Danish Broadcasting Corporation's Danish Radio Concert Hall (DR Hall). (Our March, 2009 newsletter for the opening.) The concert that evening wasn't a special gala, but a regular season concert. I had the pleasure to attend it and a post-concert reception. The DR Symphony Orchestra is the resident orchestra in the hall and plays all of its rehearsals and concerts there. The relationship of the hall to the orchestra and to the Danish Broadcasting Corporation is similar to that of NHK Hall, the NHK Symphony Orchestra and the Japan Broadcasting Corporation. However, NHK Hall is a multipurpose hall, not a concert hall and the NHK Orchestra typically rehearses not in its hall but, instead, in a separate rehearsal hall. The DR Symphony Orchestra's ability to rehearse in its hall and the concert hall acoustics of the space are distinguishing operational and acoustical characteristics of DR Hall compared to NHK Hall.
DR Hall has a vineyard style configuration and seats 1,800 persons. Berlin Philharmonic Hall is an early example of the vineyard configuration. Suntory Hall in Tokyo and Walt Disney Hall in Los Angeles are two of the many examples of halls with this shape designed by Nagata Acoustics. In a vineyard configuration, the audience seating surrounds the stage in a tiered arrangement of banks of seating-sometimes likened to the small plots of land of specialty grape vineyards. Other examples of halls designed by Nagata Acoustics and similar to DR Hall's interior layout include Sapporo Concert Hall "Kitara" and Muza Kawasaki Symphony Hall.
Suspended Acoustic Canopy and
Orchestra Risers on Stage
The DR Hall stage has two movable acoustics-related features: (1) electric-powered orchestra risers across the entire floor of the stage, including under the string sections, and (2) a suspended acoustic canopy installed in the open space above the stage. The acoustic canopy can also be raised or lowered using electric power. We designed the canopy with an electric motor to enable easy access to lighting fixtures, microphones and other equipment that are also located above the stage. Unlike the orchestra risers that the orchestra adjusts to different heights depending on the orchestra configuration and music program, Nagata Acoustics' intended the electric-powered canopy to be moved only by technicians servicing lighting fixtures, microphones and other suspended equipment.
We determined the optimal height of the suspended acoustic canopy during our room design of the hall and expected this height to stay unchanged for orchestra rehearsals and performances regardless of the repertoire or configuration of performers. Our design planning did include a scenario in which the orchestra might adjust the height of the canopy ever so slightly using the electric power provided and this possibility was taken into account during the canopy's design.
Needless to say, it's human nature that if you design something so it can be moved, someone will want to try moving it. Among the orchestra's players, those with a strong sense of curiosity expressed the desire to experiment with the height of the acoustic canopy as well as the heights of the risers and these musicians energetically persuaded the orchestra's management to let them change the height of the canopy. Both Danish Broadcasting Corporation and the orchestra's management considered the request a simple one and they too thought it fine to freely play around with the canopy's height.
The Nagata Acoustics team responsible for the project only learned about the canopy height experiments after the orchestra players had tried out a number of different configurations. Trying out different heights for the canopy put the orchestra into a state of confusion. The orchestra's players could not agree on the best height for either the canopy or the stage risers. If one player preferred a certain low height another player disagreed and preferred a specific high height. One might say that the opinions were "all over the map" with the orchestra unable to reach a consensus.
Likewise, the conductors expressed a range of preferences. It was impossible to gain a consistent recommendation from the conductors who perform with the orchestra and this contributed to the rather extreme state of confusion about how to proceed.
In general, evaluating stage acoustics is a tricky business and this becomes even more complicated when the ensemble evaluating the stage acoustics is an orchestra. An orchestra contains a great variety of instruments and their location on stage within the orchestra creates a unique environment for each player. The music parts played by each musician differ from the parts played by their colleagues and the conductor plays a critical role in how the orchestra sounds and performs. Each musician comes to his or her opinion of a stage's acoustics through the context of a complex set of conditions that varies from musician to musician.
Another complicating factor is the phenomenon that as the musicians gain experience on a stage, their evaluation of the stage acoustics changes. Even on exactly the same stage and under the same conditions, as the musicians gain more experience practicing and performing in the space-that is, as time passes-their opinion of the stage acoustics changes.
It's not unusual to hear or read about "the best on-stage acoustics". However, there is no one-size-fits-all solution for the "best stage acoustics". For example, the acoustical characteristics on-stage at the Vienna Philharmonic's Musikverein differ significantly from the on-stage acoustics at the Berlin Philharmonic's Philharmonie Hall. For each orchestra and each hall, there are unique stage acoustics that enable the orchestra to comfortably play at its best.
When I was contacted by the DR Orchestra about the confusion and dilemma that experimentation with the stage canopy had created, I immediately advised an end to the experimentation and requested that the acoustic canopy be moved to the height specified in our design documents. I recommended that the originally specified height be used as is for at least one full year without making any adjustments. After the orchestra would invest this period of time to gain experience in the hall, if necessary, small, incremental adjustments could be considered, keeping in mind that achieving the best on-stage acoustics requires following the essential and important process of practicing and performing on the stage over a period of time.
When I visited the hall in January for the concert on the hall's 5th anniversary, considerable time had elapsed after the series of events that began with the orchestra experimenting with the canopy's height, becoming confused about the proper height, contacting Nagata Acoustics and implementing our prescription of a "no changes at all" period. After the January 20 concert, I participated in a productive meeting with the orchestra players and Danish Broadcasting Corporation representatives. I learned that the orchestra players' temporary dilemma was for the most part a thing of the past. The orchestra has settled into the on-stage environment. Nagata Acoustics' role is now to be available to the orchestra to discuss-if necessary- how adjusting the position of the acoustic canopy would affect the on-stage acoustics and to work with the orchestra as it cautiously considers if this is a possibility it wishes to pursue.
By Dr. Keiji Oguchi
Düsseldorf is one of Germany's most famous cities and today has a mix of contemporary and historical buildings that attract both business and tourism. It also has the largest Japanese expatriate community in Germany, making me feel very much at home whenever I visit. I recently toured the home hall of the Düsseldorf Symphony Orchestra to observe at first hand its acoustically interesting and successful 2005 renovation.
<< History of Tonhalle >>
Exterior of Tonhalle
The history of the Tonhalle building dates back to 1926. The building was originally built as a planetarium. After sustaining damage during World War II, a portion of the building was renovated for use as a multipurpose venue. In 1970, a project further renovated the war-damaged building, retaining the dome ceiling while adding a large acoustical canopy above the stage and changing the venue into a concert hall for classical music.
In 2005, the building underwent another major renovation, this time to remove asbestos and improve fireproofing. The 2005 renovations also eliminated acoustical issues caused by the hall's dome shape.
<< The Pre-2005 Tonhalle Sound Focusing Problem >>
Interior of Tonhalle
In the May, 2000 edition of this newsletter I wrote about the focusing phenomenon that invariably occurs somewhere in any circular or elliptical-shaped room because of these shapes' significant amount of concave surfaces. Tonhalle Düsseldorf's cylindrical shape topped by a dome of approx. 20 m. (66 ft) diameter makes it a paradigmatic example of the kind of hall shape that experiences sound focusing problems.
Before the 2005 renovations, Tonhalle had a sound focusing problem known as the "poltergeist that knocks at the door (Klopfgeist)". The dome's concave wood surface caused sound focusing of sound reflections in one area of the hall. According to a report by the acoustical consultant of the 2005 renovation project, Mr. Vercammen of Peutz Bv, in the hall's problem area, sound focusing from the dome had a 110 ms delay compared with the direct sound. Also, Mr. Vercammen reported observing a larger peak of 14 dB for the sound focusing compared with the direct sound on an ETC (energy, time and curve) graph.
<< The Remedy for Tonhalle's Sound Focusing Problem>>
Metal Fabric Surface
In my May, 2000 article on this topic I discussed two strategies for mitigating sound focusing: (1) Disrupt the smooth arc of the surface causing the sound focusing; (2) Add scattering and/or sound-absorbing treatments to the concave surfaces. For the 2005 renovation, Peutz adopted the strategy of leaving the roof dome intact and replacing the interior dome ceiling with an acoustically-transparent ceiling that looks like a dome shape from the audience perspective.
Peutz's design worked within the constraints of the dome-shaped roof to reflect the sound either directly downward or to redirect it to points on the ceiling other than those in the direction where the sound focusing would occur. Before implementing the design, Peutz validated its effectiveness using acoustical scale model test.
Within the constraint of inside the dome roof, Peutz constructed a new ceiling which consists of horizontal donut planes and vertical rises with zigzag shape. This design is thought of apparently to employ both of the strategies mentioned above.
<< My Visit to Tonhalle Düsseldorf >>
A while ago I had the opportunity to visit Tonhalle. Indeed, the visual ceiling appears to have a dome shape. However, in fact, it has an acoustically transparent, metal wire mesh surface. The blue lights distributed down from the actual complex ceiling behind the metal mesh create a magical-looking interior. The wire mesh of the ceiling continues down to the wall behind the audience seating and I could see through the wire mesh that the wall has a complex arrangement of sound reflecting angles.
In addition, Peutz's design includes other details to minimize the surface area that would direct sound to the center of the dome. They used cylindrical piping for the support structure of the wire mesh and, on the circular balcony's balustrade wall that faces the stage, they added a line of protruding elements made of glass.
During an orchestra rehearsal I attended, I sat in a number of different hall seats. I had the impression that even for pulsive sounds by percussion instruments, the sound focusing phenomenon has pretty well been eliminated. I was able to confirm at first hand that the 2005 renovations were a big success. The literature on this hall's design-which preserves the look of a dome shape while removing any sense of a sound focusing phenomenon-provides good material on mitigations for halls of this shape.
The Tonhalle URL is http://www.tonhalle-duesseldorf.de.
Nagata Acoustics Salon Welcomes Mr. Joji Kuriyama, Digital Audio Device Pioneer
By Kosuke Suzuki
Last month we invited Mr. Joji Kuriyama to speak at our Tokyo main office. Mr. Kuriyama is one of the foremost pioneers of digital audio devices. During his visit, Mr. Kuriyama gave a seminar and retrospective about some of his concert hall-focused work. Previously, in 1990, the Japanese-language version of this newsletter introduced readers to a world's first digital mixing console at the Vienna State Opera House, and Mr. Kuriyama was its project manager at the time. In Japan and around the world, "Joji Kuriyama" is a well-known and highly respected name in his field.
<< The TOA SAORI DSP >>
Mr. Joji Kuriyama
Mr. Kuriyama began thinking about building a digital mixer even while he was still a student. After earning bachelor's and master's degrees at Kyushu Institute of Design, he joined the electronics manufacturer TOA Corporation where he was initially assigned to the Telephone Switch Department and gained electronics expertise.
After his initial assignment, Mr. Kuriyama became engaged in digital signal processing (DSP) development. In 1989, less than 10 years after starting his employment at TOA, Mr. Kuriyama completed development of the SAORI DSP, which continues its strong popularity to this day.
<< The Vienna State Opera House and Mr. Kuriyama >>
On one evening during the time Mr. Kuriyama was developing SAORI in Japan, the Vienna State Opera House's "tone meister", Mr. Wofgang Fritz, was having a dinner with TOA Corporation's president in Vienna. Mr. Fritz told TOA's president about his idea to replace the opera house's sound system with one that is entirely digital. TOA's president remembered the work his young employee Mr. Kuriyama was pursuing and called Mr. Kuriyama, "What is a digital mixer? Can you make such a device?"
Mr. Kuriyama explained the main concept and replied, "Yes, I can make it." Soon thereafter, TOA Corporation put Mr. Kuriyama on a plane and sent him to Vienna all by himself to meet with Mr. Fritz. Mr. Kuriyama was just one among a number of contenders for this prestigious work. According to Mr. Kuriyama, when he arrived in Vienna it was still very uncertain whether he would be selected to build the digital sound system.
Mr. Fritz took Mr. Kuriyama to the opera house sound control room where a copy of "The Magic Flute" opera score lay open for the night's performance. Mr. Kuriyama began reading the score and he asked Mr. Fritz the meaning of handwritten marks that had been added to the pages. Mr. Fritz was very surprised since none of the engineers that had come before Mr. Kuriyama could read an opera score and, as Mr. Kuriyama recalls, Mr. Fritz's demeanor softened noticeably.
Mr. Kuriyama recounted that he can read opera scores because of a required course he took in college. Mr. Fritz's awareness of Mr. Kuriyama's music-reading skill led to a friendship between the two men that grew into a trusting relationship and to the opera house awarding the project to TOA.
<< The Vienna State Opera House's Digital Sound System >>
The contract with the Vienna State Opera House required Mr. Kuriyama to complete the new sound system in no more than two years. During this short time frame, and starting from a 100% analog system, both Mr. Kuriyama and Mr. Fritz agreed that the new system must be entirely digital. They researched and studied innumerable technical papers and treated every detail of the design and implementation with uncompromising dedication to building a complete and high quality digital sound system.
For example, because ambient noise is extremely minimal in concert halls and opera houses, Mr. Kuriyama needed to make sure that when there are no input signals to the loudspeakers, the amplifier doesn't emit residual noise. He added an external relay control function for this purpose. Also, while today we may think of touch-panel displays as something ordinary, when Mr. Kuriyama used them a quarter century ago they were an extraordinary innovation. Even the name of the console was ahead of its time, the letter "I" for integrated and "X" for mix was combined to form the "ix" model name of the mixing console series.
<< Mr. Kuriyama's Passion for His Profession >>
Mr. Kuriyama's story epitomizes how a person can grasp an opportunity that comes along seemingly by accident and turn it into the realization of a dream. He never compromises his high standards and has created devices that have stood the test of time and retained their popularity.
Listening to Mr. Kuriyama, it was obvious that he continues to pursue his field of interest with passion and enjoyment. I was moved to my core by his enthusiasm. By following in Mr. Kuriyama's footsteps, I believe we should be creating venues that will be loved and used for a very long time although the construction industry operates mainly with both schedule and budget constraints these days.
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
2130 Sawtelle Blvd., Suite 308
Los Angeles, CA 90025, U.S.A.
Tel: +1-310-231-7878, Fax: +1-310-231-7816
75, avenue Parmentier
75011 Paris, France
Tel: +33 (0)1 40 21 44 25, Fax: +33 (0)1 40 21 24 00
[ Japanese Version ]