Concert Hall Acoustics - Essay Example

Concert Hall Acoustic Acoustic has been an important influence on music. It has a vital role to play in creating the sound effect in the concert hall. The sound quality of a performance is dependent upon the acoustic of the space surrounding the artists as well as the audience. Even if the quality of the performance is amazing there is no use of it if the sound in the hall is with poor acoustic and even if the greatest artists and musicians come together to play the music there is no guarantee whether they would be able to create the good effect because of the sound quality. There performance can be good but not outstanding. But if these musicians play in the concert halls like Boston Symphony Hall or Amsterdam’s Concertgebouw or Vienna’s Grosser Musikvereinssaal, then that would be amazing performance no doubt. It means that good performance depends upon the excellent combination of the greatest musicians as well as the good hall acoustic. Computational acoustic is the science which can be used to study concert hall acoustic. The creation of a beautiful music is rather an art than a science. Now a day the concert hall design is based on the involvement of the combination of precedence, engineering, and art. It is regarded as an ideal concert hall where there is a fine blend of acoustician and architect and where the engineering make it easy for the art to embellish. The acoustics of any concert hall is basically consisting of three major factors: 1. volume 2. Equalization 3. Reverberation. 1. Volume: The sound in the concert hall has two types of volumes: directly radiated sound and reflected sound. Directed sound is a primary sound which reaches to the ears directly while the reflected sound reaches the ear after being reflected of the various mediums such as walls, Ceiling and floor. 2. Equalization: Equalization is a further description of volume. Sound consists of vibrations which can be called as the frequencies and ideally the concert hall should not have the high frequencies. It has to have on the other hand a very placid, melodious and warm sound. The musicians can get the freedom in the production and articulation of the sounds if the sound is mellow. Thus the equalization is the major factor in any acoustic and in sound and it can change the quality of a sound. 3. Reverberation: The sound quality that is called reverberation is the result of the first arriving reflected sound. It is the process of the reflected sound bouncing back all reflecting surfaces until it stops. (Concert Hall Acoustics, An Explanation of the factors involved in Acoustics with an analysis of those Factors in Relation to San Francisco’s Davies Hall .) The technique of reverberation was first applied in Boston Symphony Hall which was developed by Wallace Sabine hundred years ago. And this Hall is regarded as one of the best auditorium in the world. At the time of designing the hall the acoustic engineers have to look at the various factors which include the background noise level, the amount of reverberation, the amount of sound arriving from the side, In modern concert hall science and engineering are used to make an acoustic which increases artistry of the musicians. Concert hall Acoustic is an old technique and research has been done over last century on this subject. The acoustic creates a tremendous effect. Outdoor music can be popular but the sound quality of the outdoor music is always poorer than that of indoor music. In outdoor music the audiences get the sound directly from the orchestra with no reflection from the walls or ceiling or floor. In concert halls generally the sound can be altered by placing treatment on the walls and ceilings. Three basic forms of treatment are there. They are large flat surfaces, absorbers, and diffusers. Absorbers are not used in concert halls as they remove the sound energy from the space. In concert hall even the smallest sound energy is also very important because there is a limit for the energy produced by the orchestra. There are many processes involved in the design of architectural concert hall which comprises of determining the volume, shape proportions, materials, and finishes of acoustically critical spaces. Applied research, site measurements and analysis of concert hall acoustics data, hands-on lab testing of materials and equipment, and studies with physical and computer models are all part of the creative process of concert hall acoustics. The role of surface diffusers in concert halls has been as issue of discussion and debate. One concert hall designer claims that too much diffusion is detrimental to the sound quality of the upper strings while the other contradictory view the disappointing acoustics of certain major halls on a lack of surface diffusion have been blamed by the engineers. Use of Diffusers in Concert Halls Diffusers are used in various ways. They can be used to lessen echoes which arise from the back walls of auditoria. It will take a long time for the sound to reach from the stage to the rear wall of the concert hall. There can create an echo if the strong reflection comes back from the rear wall to the front of the wall. The echo problem in the old concert halls could be eliminated by placing absorbent on the rear wall to absorb the acoustic energy. It would definitely be able to prevent the reflection occurring and thus to solve the echo problem. Such method has already been adopted in London’s Royal Festival Hall. But here the absorption removes acoustic energy and thus reduces the sound of the orchestra. That is why the modern solution now is used and that is the use of diffusers to break up and disperse the troublesome reflections and it can be done without the loss of the acoustic energy. The examples of this new solution are Carnegie Hall in New York and Glyndebourne Opera Hall in UK. The architectural trend changed in twentieth century and large expanses of flat areas appeared in many concert halls. The post war concert halls in UK have very little embellishment. In those days the general style was to produce clean lines following modernist style but these surfaces had either very less or no diffusing capability. The Symphony Hall in Brimingham in UK is there which has a little surface diffusion. Manfred Schroeder is the pioneer in the development of modern diffuser. He was one of the skilled acoustic engineers of twentieth century. He developed the phase grating diffuser. It is also known as the Schroeder diffuser. One of the pioneer applications of these diffusers is used by Marshall and Hyde in Michael Fowler Centre, New Zealand. Here they have used large overhead reflectors to give the audience the early reflections in the balconies in a revolutionary design. Here the large volume partly comes from the space behind the diffuser. It has been established that lateral reflections were important in concert halls because they promote a sense of envelopment or spatial impression in the room. (M. Barron: The subjective effects of first reflections in Concert Halls-the need for lateral reflections’ journal of sound and vibration, 1971, 15, 475-494) Thus Marshall and Hyde realized the need for lateral reflection to apply diffusers to the large overhead surfaces instead of using the flat reflectors. By the mid 70s in one research of concert hall acoustic it was shown that the most important qualities of a good hall are that the sound field is diffuse or well mixed and the sound reaches the listeners’ ears sideways. And this international trend arrived with the design of the Sigyn Hall in Finland. Hundred years ago W. C. Sabine took the first initiative in the evaluation of the acoustical qualities of the concert halls in numbers with his famous equation of reverberation time. At first the invention was based on the monoaural or monophonic properties which would consist of factors like fullness of tone, clarity, loudness, and timbre. After 1960 it was discovered that stereophonic qualities are critical when trying to achieve excellent acoustics. Computer Revolution And Acoustical Design. The traditional tool in hall design is the scale model. In the advance technology and the use of computer has brought incredible revolution in the hall design technique and now instead of scale model numerical models have been used now a days. As compared to scale model computer models have innumerable advantages. Computer model is built numerically from corner points and plane surface. The best example of acoustical computer modeling and designing of acoustical improvement is Turku Concert Hall. The project was carried out during the year 1998-2003. During this project 20 different computer models were made to examine the improvement of the quality of the Concert Hall. Turku Hall of Finland was built in 1952. There were some acoustical problems in this hall such as disturbing back wall echo. But later on acoustical design and computer modeling was developed. The creation of the concert hall which is acoustically pleasing was a challenge and that skill was possessed by some fistful builders. The senior acoustician of Davies Hall, Robert B. Newmann, said that "the acoustic of every new concert hall is an experiment. But the computer has facilitated the skill. Using the proper rules of physics the acousticians have devised the computer programs which can easily predict the behaviour of the sound in the concert halls. Sources: 1. Concert Hall Acoustics, An Explanation of the factors involved in Acoustics with an analysis of those Factors in Relation to San Francisco’s Davies Hall . http://www.anstendig.org/Acoustics.html 2. http://www.ark.fi/ark4_96/acoustics.html 3. http://www.jaffeholden.com/concert_hall_acoustics.html 4. http://www.acoustics.salford.ac.uk/acoustics_info/concert_hall_acoustics/ 5. M. Barron: The subjective effects of first reflections in Concert Halls-the need for lateral reflections’ journal of sound and vibration, 1971, 15, 475-494 Read More