Multi Purpose Halls in History
Along the history, specific building designs have been developed and some specific functions for Acoustics in Multipurpose Halls. Musical events were carried out in the prom halls and with the rising attention on music special building types were started to be designed for musical functions. Foundation of the new designs obviously based on the prom halls in which the initial events had been made. Had started with this halls’ rectengular shape and then tried new approaches. Growing acoustic science as music came into prominence and new developing specialists pointed out some faults in different types of buildings, meanwhile bringing backs occured with progress by the help of developing and accumulating knowledge. Primarily multi purpose halls appeared by concert, opera, theatre halls’ being converted. The trigger of it was the economical reasons. Maintenance of a building which has multiple purpose was less costly than several buildings’ maintenance which have one purpose for each. In this case multi purpose utilization in a hall became a requested feature. The acoustical requirements for music and speech are different than each other and sometimes even the contrary. Priority is to find the least common denominator and this is rough to provide. Most of the time one of the functions come to the fore and design way is determined in accordance with this one more coherent than the other function.
In the speech halls, speech is supposed to be made easily without a reinforcement sound system and intelligibility of the speech is a requirement which should be provided. Sound levels of male and female are different. Distinguishing of these sounds is an important discipline to provide.
Computable parameters are the objective ones which are being affected by the physical conditions. Subjective parameters are not computable and these are used to bring an explanation to the different perception of acoustics in a room by the audience. Some of the objective parameters are as followed; reverberation time (T30), early decay time (EDT), binaural quality index (BQI), strength of sound (G), bass ration (BR), initial time delay gap (ITDG), early lateral fraction (LF80), definition (D50), clarity for music (C80), centre time (Ts)… Some of the subjective parameters are as followed; intimacy, liveness, warmth, loudness, spaciousness, brilliance…
Influences of the design process on acoustical comfort and performance should be remembered and the optimal case should be provided. The design parameter variables at hand; material effect, floor rake, terrace seating, terrace walls have an impact on the total energy in the halls, the early and total energy which is receiving to the receivers and consequently also has an impact on acoustical parameters.
The seatings which have better acoustical comfort than the other seats are back group seats. Because these are the closest ones to the back wall and ceiling so that they have more of the early reflections, lateral reflections and early energy. As a result, hearing conditions here are better than the other seats (front and middle group) in terms of speech intelligibility, speech transmission, envelopment by sound and intimacy of the hall. Concave surfaces cause focusing defect in the hall. In order to keep focusing defect not increasing, the form of the ceiling should be picked in a way, in which it won’t cause focusing. Absorbing and reflecting materials that are used on back walls to eliminate or minimize these defects (echo and focusing) should have a high scattering coefficient as well to contribute to the solution of these defects. Deep floor rake increases the echo defect by providing longer reflection paths, it should be kept in mind. It can contribute to the solution of echo problem to keep smaller the radius of the circle on the plan plane. Although the ceiling is delivering the reflections to the receivers geometrically, in order to increase the amount of the total energy and reflections, ceiling reflectors can be used. Should have care on usage of the terraces in the hall.
It should be remebered that materials which are used for acoustical control contribute to taking under control the sound decrease in a hall and acoustical comfort. Materials should be used on proper building components with proper absorbing, reflecting and scattering coefficients.
Acoustics in Multi Purpose Halls