Sound Travels, Shaping Architecture
Sound Travels, Shaping Architecture
  • Cho Ku Yun-ji 기자
  • 승인 2008.09.06 01:06
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On 21 November 2007, a new music hall for Korean traditional music opened.  This, called ‘Seoul Namsan Gugakdang,’ was built by the Seoul city government with the aim of making a typical Gugak music hall.  Unlike the National Center for Korean Traditional Performing Arts located at the Seoul Arts Center, Seoul Namsan Gugakdang is made up of Hanok (Korean traditional house)-style materials inside and outside the hall.  This not only enables the audiences to enjoy the very traditional Korean-style hall, but also maximizes the sound effects of the Korean traditional music, Gugak.  It has been designed specifically for the Gugak sound, with regards to reverberation time.  According to Wikipedia, when sound is produced in a space, a large number of echoes build up and then slowly decay as the sound is absorbed by the walls and air, creating reverberation, or reverb. By adjusting reverberation time to exactly 1.2 sec when empty, the audience could appreciate the traditional music in the best environment without the use of microphones.

Very Soft, Very Comfortable and Very Well-absorbed

Have you ever thought of the reason why chairs in theaters are soft?  Is it for your convenience during the performance?  It could be partly true.  In fact, the soft seats are designed to play an important role in reverberating echoes.  This form of science, called Architecture Acoustics, was begun on 29 October 1989.  A physicist named Wallace Clement Sabine was conducting an experiment on reverberation time at Fogg Art Museun in Harvard University.  To reduce the reverberation time which was not suitable for lectures, he used sound-absorbers as a solution. 

Reverberation time is decided by many variables including sound-absorbers and even the number of audience members.  To make full use of a hall, there should be a proper reverberation time depending on the purpose of the hall.  Generally, it is assumed that for a space for performing music, the proper reverberation time should be 1.5~2.5 seconds.  However, in the case of a lecture room, the reverberation time is based on 1~1.5 seconds.  In a theater or music hall, as the number of people is not always the same, the soft chairs also play an important role as sound absorbers.  With the help of those chairs, we could be offered not only comfort, but the best condition for appreciating music.

Secret Hidden in Ancient Greek Theaters

The ancient Greek theater, dating back to the 4th century B.C. and arranged in 55 semi-circular rows, remains the great masterwork of Polykleitos the Younger.  Audiences of up to an estimated 14,000 have long been able to hear actors and musicians – unamplified - from even the back row of the architectural masterpiece.

How this sonic quality was achieved has been the source of academic and amateur speculation, with some theories suggesting that prevailing winds carried sounds or that masks amplified voices.  It's in the seats.  Researchers at the Georgia Institute of Technology have discovered that the limestone material of the seats provide a filtering effect, suppressing the low frequencies in voices, thus minimizing background crowd noise.  Furthermore, the rows of limestone seats reflect high frequencies back towards the audience, enhancing the effect.

Researcher Nico Declercq, a mechanical engineer, initially suspected that the slope of the theater had something to do with the effect.  "When I first tackled this problem, I thought that the effect of the splendid acoustics was due to surface waves climbing the theater with almost no damping," Declercq said. "While the voices of the performers were being carried, I didn't anticipate that the low frequencies of speech were also filtered out to some extent."

However, experiments with ultrasonic waves and numerical models indicated that frequencies up to 500 hertz (cycles per second) were lowered, and frequencies higher than 500 hertz went undiminished, he said.  (

Interesting Science Story in Architecture, Lee Jae-in, Sigongsa

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