Help needed with acoustics of chapel

[buckshead]

If you know anything about acoustics, can you refer to my question in the Sample Discussion

[schneb]

If you know anything about acoustics, can you refer to my question in the Sample Discussion

I can help. But not sure where to go. How about a link?

[buckshead]

I put the following on elsewhere in the forum


We are in the process of designing renovations for a local Methodist Chapel. The building is also used by a famous local (and international) male voice choir. (for practice)

The ceiling of the building needs to be replaced and insulation added.

The problem: The choir is very worried about the work messing up the acoustics of the building. The ceiling is currently plaster laid on laths fixed to joists, about 150 years old. If we replace this with plasterboard, which is softer, will we spoil the sound?

Whatever we do will be wrong, (we realise that) but we would like to be less wrong. (if possible) .

Anyone tell me about acoustics of this type of roof. It is also sort of barrel vaulted but will be altered to flat.

Am I on a loser here?

[schneb]

The ceiling of the building needs to be replaced and insulation added.
Considering what it costs to heat and air condition such a facility, I can understand.

The ceiling is currently plaster laid on laths fixed to joists, about 150 years old. If we replace this with plasterboard, which is softer, will we spoil the sound?
Plaster is basically concrete. It is extremely hard, yes, and there will be some change. However, most of your acoustic sound will be based on the design of the ceiling more than what it is made of. As long as you do not blow cottage cheese ceiling coating, you should be fine. Rather, keep the ceiling smooth and painted.

If the current ceiling is still good (ie, no falling debris) consider insulating with injected foam. It would save a LOT of work and debris clean up. Using Urethane foam is more costly, but it is a much better insulator and will not matte down over time like fiberglass. Result? More efficient insulation, no loss of current acoustics.

Whatever we do will be wrong, we would like to be less wrong. (if possible).
Urethane injection is what I would recommend if at all possible.

Anyone tell me about acoustics of this type of roof. It is also sort of barrel vaulted but will be altered to flat.
THAT will cause all the harm you fear. All the acoustics will be altered. This is an inexpensive answer that will solve insulation woes, but will ruin the beauty and sound of the interior. If it were my facility, I would tear off the roof, insulate accordingly, then reroof. If the interior ceiling still needed work, I would talk to a REAL pro about recoating the plaster. Talk to a restoration professional, not a drywaller. Dry wall guys are get in, get it done, then leave. They do not understand or care about acoustics or building aesthetics.

Am I on a loser here?
Of course not, you may just be this facility's savior. But, if the barrel ceiling is lost, your ambiance (both acoustically and aesthetics) will be. Sound bounces. Currently, the reflection is omnidirectional because of the barrel shape. Change this to flat and you focus the reflection and lose the omnidirection. Not only that, but your interior will look, what professionals term "remuddled". I would highly advise against it and do more homework for an alternative that preserves the look and sound of this facility.

Is there an interior shot available online?

IMHO (as always), Schneb

[GrahamKeitch]

Hi Derek,

I can't really help with the acoustics questions - but a lot of what schneb has said would appear to make sense. As a singer, I can understand the concerns of the choir - although I wouldn't have thought this would be a problem for rehearsals. Live performance and recording is another matter. Is the building listed? If so, you will be restricted in what you can do internally as well as outside. Also, in C of E churches, you have to apply for faculties before undertaking any work but I'm not sure this is the case for a Methodist chapel. Anyway, good luck.

Regards, Graham

[buckshead]

Thanks everyone. Graham yes we are in touch with Property Services for the Circuit and have permission. As usual there is insufficient funds for this work or at least for anything more than the intended use as a chapel.

The building is being altered to act as a community centre as well as a chapel. In this way it will generate more funding with which to maintain the building for the future.

Use of the building by the choir is a secondary facility. The building is too small and the funds too tight to employ specialist acoustics.

The Architect wants to flatten out the ceiling, but there are really weird trusses in the roof and this would be difficult so we will stick to the main shape I believe. I just wanted to confirm my opinion about the effects on the sound quality and everyone here seems to agree with me

Thanls for the help

[schneb]

Does the community have any regard for the structure? Perhaps a fundraiser to administer the improvements? I live in a historic city in Southern California, and we must fight often to preserve our historic sites. Just need to find the right people willing to stand up for the structures.

Sometimes you just need to be creative. Here is a consideration that I would offer. A Roman drapery canvas. Basically, you have a tight, horizontal cable--one on each side of the main sanctuary. You have a curtain that is on rings that slides on the cable from one side to the other. It is sewn in such a way that panels droop down in sections. During rehearsals, it can be pulled back for the acoustics. During town meetings, it can be pulled out for warmer gathering aesthetics and less room reverb. Minimal damage to the existing structure, yet designed to be expandable to other purposes.

[gnair]

Some of the points are really excellent here. However, when musical acoustics are involved, there is no substitute for a professional acoustician being involved as a consultant. In 2002-2005, I was in charge of the design and construction of my university's new $12m concert hall. NO architect knows enough to safely predict what his/her actions are going to do to the building's characteristics.

It seems like a lot of money to spend on a consultant, but in the end, no consultant is like being your own lawyer in a trial. Don't do it.

GN


Does the community have any regard for the structure? Perhaps a fundraiser to administer the improvements? I live in a historic city in Southern California, and we must fight often to preserve our historic sites. Just need to find the right people willing to stand up for the structures.

Sometimes you just need to be creative. Here is a consideration that I would offer. A Roman drapery canvas. Basically, you have a tight, horizontal cable--one on each side of the main sanctuary. You have a curtain that is on rings that slides on the cable from one side to the other. It is sewn in such a way that panels droop down in sections. During rehearsals, it can be pulled back for the acoustics. During town meetings, it can be pulled out for warmer gathering aesthetics and less room reverb. Minimal damage to the existing structure, yet designed to be expandable to other purposes.

[schneb]

Don't do it.

If you are going to spend that kind of money for a concert hall, I whole-heartily agree. However, in the context of the question and the lack of budget, I felt it required alternative thinking and not remuddling. For example, the use of the horizontal Roman curtain could possibly solve the acoustic issues for a community center, while preserving the historic and acoustic nature of the building. And that at a minimal cost.

[gnair]

Ah, Schneb ... what I wrote was not an attack on your ideas ... many of them are excellent. Our concert hall has not been the only acoustic question that I've been involved with. People always assume that an acoustician will cost too much ... a simple consult can go a long way.

I do wish them luck with the project.

G


If you are going to spend that kind of money for a concert hall, I whole-heartily agree. However, in the context of the question and the lack of budget, I felt it required alternative thinking and not remuddling. For example, the use of the horizontal Roman curtain could possibly solve the acoustic issues for a community center, while preserving the historic and acoustic nature of the building. And that at a minimal cost.

[schneb]

Ah, Schneb ... what I wrote was not an attack on your ideas ... many of them are excellent. Our concert hall has not been the only acoustic question that I've been involved with. People always assume that an acoustician will cost too much ... a simple consult can go a long way.

And did take it that way either. On the contrary, you are right. Seems folks think of acoustic consultation as being an afterthought, when it reality it should be the first thought. Lets hope enough folk think of it before the final design of a church, auditorium, or music hall!