The science of modern concert-hall acoustics was born in the late 1800s and early 1900s in the United States. The father of architectural acoustics was Wallace Clement Sabine, an assistant professor at Harvard who helped to plan the internal acoustics of the new Boston Symphony Hall, erected in 1900, and is considered to have be one of the best concert halls for its acoustics in the world.
By testing various halls using seat cushions, people, a pipe organ, various other materials and a stop watch, Sabine carefully measured the time required for different sound frequencies to decay within the various spaces. Today, there are six attributes in considering the acoustics of concert halls. These six attributes are the standard for which all concert halls are based.
1. Reverberation Time
According to Leo Beranek, the musical quality of a concert hall is closely related to its width. Additionally, audiences absorb a considerable amount of sound. The number of people spread out over the area of the concert hall is one of the key determining factors in effective acoustics.
2. Concert Hall Width
The width of the concert hall directly affects the ability of the audience to hear the performers and “feel” their proximity. Listeners should hear the music as if they are close to the performers on stage. If your hall’s ceiling is shaped in a way that it does not reverberate sound correctly, you might benefit from contacting a roofing company to make it work better.
The more audience members there are, the less sound energy each person receives and absorbs. So when the desired reverberation time is achieved, the loudness of the hall is set.
4. Diffusion of Sound Waves
Sound wave diffusion is affected by irregularities and ornamentation on the surfaces of the hall which reflect the sound waves. In a hall with sufficiently irregular surfaces, such as coffered ceilings, statues, hanging light fixtures, etc., high frequency sounds scatter as they reflect and renders the music as softer and more pleasant to the audience.
5. Spatial Impression
When sound reflects laterally and reaches the audience members from the side, it gives the auditory illusion of being enveloped in the sound. So a narrowness of a hall will contribute to the impression of spaciousness in the sound.
6. Early-to-Late Energy Ratio
This ratio is determined by measuring the energy of the direct sound and subsequent sound in the first 80 milliseconds and the sound energy that arrives after. If the early sound is too strong, the reverberation may be too weak to yield the appropriate resonance which is appealing to audiences. Conversely, if the energy in the reverberant sound is too strong, the music gains a “bathroom” quality.
There are various aspects which affect the internal acoustics of a concert hall. The father of modern architectural acoustics was able to pinpoint six attributes which work together to help or hinder the acoustics of the space. Through careful planning, the layout of the concert hall can be developed to promote excellent acoustics and facilitate an excellent concert experience for all.