How do reflectors in auditoriums improve sound quality?

[dreit]

In many theaters and auditoriums some of the ceilings are concave or have things hanging from them. How does this enhance the traveling of sound?

 

[schip666!]

Actually concavity would be a problem as it focuses sound making coverage uneven -- unless it's well planned in advance. Convex (arching out) surfaces are often hung over, say, orchestras in order to disperse the sound more evenly. Dangly bits might disperse or absorb, both reasonable hopes in controlling reverberation and evening out the frequency response of a room. All these effects are analogous to the way mirrors and other objects affect light, they just need to be bigger to affect sound.

 

[mishrashubham]

But wouldn't a concave ceiling (concave as observed from the inside) help distribute sound coming from a point source. Something more along the lines of the following image.

 

[dreit]

Yeah, I thought concavity would have more of a projection effect like the image above. I guess it really depends on how the stage opens up into the actual theater.

 

[schip666!]

Yes you are right...I was thinking of a spherical concave reflector which would tend to focus rather than disperse. I forgot about all those old-timey bandshells which have some kind of concavity behind the stage. The shape in the lovely drawing provided by mishrashubham would seem to do the job we need. But it's tricky because you don't always have a point-source soloist to distribute.

 

[JDługosz]

The http://www.dallasculture.org/meyersonSymphonyCenter/photos.asp" shows a big thing hanging above the stage where I go. It can be moved into different positions.

This concert hall was a big deal when it was first built, in terms of having good sound.

Wikipedia summarizes, "a system of canopies weighing more than 42 tons is suspended above the stage and can be raised, lowered, or tilted to reflect the sound throughout the audience chamber.[5]"

 

[sophiecentaur]

A serious problem in big buildings, particularly high ones with domed roofs, is the echo from the ceiling. Whilst reverb is nice and atmospheric, a distinct echo is bad. In the Royal Albert Hall, there are 'mushroom' reflectors, suspended at various heights, to break up a single, annoying, echo into a random set of small echos which still give the benefit of a large auditorium but without the echo problem.

In very large auditoria /ums, and in outdoor venues, a reflector overhead can improve the listening for people at the back but they can colour the sound. This doesn't matter because the 'purists' all spend a lot of money and sit up front.