Concert Halls with Natural Acoustics

Old concert halls with natural acoustics are continuously reconstructed and new ones are being built worldwide. However, the number of recognized halls with good sound increases only slightly, despite the fact that, due to the development of computer technology, engineers have a large amount of affordable measuring equipment of all kinds and computer acoustics modeling software.

The fact is that the hall acoustics design is not only engineering work in the field of construction. It also includes a creative component, similar to the work of an architect that sometimes allows combining the features that are beautiful for the eyes and useful for the ears even on an intuitive level. Designing halls with natural acoustics is an art, the highest level of acoustics engineer's work. Unlike all kinds of halls with electrical sound amplification, where the sound power of the source is not important, in the halls with natural sound, this is the main value. The task of an acoustic engineer is the ability, using space planning solutions and properly placed interior elements, to "bring" these vibrations to every viewer anywhere in the hall without distortion and significant attenuation. At the same time, over the past 50 years, the viewers themselves have been already spoiled enough by the powerful and rich sound produced by the amplification equipment. Therefore, they perceive captiously, you can even say capriciously, a live sound in the presence of the slightest defects therein. As with commercial cinemas, more and more new concert halls for natural sound are "muffled". They use more special sound-absorbing materials than they shall. Therefore, the sound becomes weak and faint, even if the shape and proportions of the hall itself are quite successful.

Therefore, it is during the construction and reconstruction of halls with natural acoustics a real acoustic engineer becomes an uncompromising Cerberus and, to the dismay of manufacturers of specialized sound-absorbing materials, jealously defends the interests of good sound.

When designing such premises, the following principles should be observed:

The shape and proportions of the hall should be selected based on the requirements of the best diffuseness (uniform distribution) of sound in the room. For halls with natural acoustics, an ideal ratio of length, width, and height of the room is equal to the "golden section" proportion: 1:0,62:0,38.
Depending on the hall volume, the reverberation time in it must be within the range as recommended for halls with natural acoustics.
Surfaces in the area of the sound source - portals around the stage and an apron above it - can act as reflectors of sound, directing sound energy to distant parts of the hall. The hall interior shall contain a uniform and, most importantly, balanced alternation of sound-absorbing and scattering surfaces.
Any acoustic defects, such as "fluttering" and "theatrical" echo, must be avoided in the hall. These defects occur in the presence of parallel sound-reflecting surfaces, as well as in the presence of reflective surfaces of a large area, which are placed at large distances from the sound source and directing the sound back to the performer, but with a long delay.
The interior of the audience hall shall use fireproof and eco-friendly materials suitable for long-term operation, featuring a well-known and stable acoustic performance.

Computer and physical modeling play a separate role in the design of premises with natural acoustics. Preliminary construction of such models makes it possible, even at the design stage, to identify significant acoustic defects and problem areas of a hall, to consider various solutions, and to choose the best one.