What ceiling/roof is best?

P

phlopip

New member
Just curious which roof shape is best to control the sound, a pent roof such as most houses have or flat or higher one side than the other so kind of slanted?
 
hmmm...

not sure dude.

I'd think angled upwards in the middle but like I said, not sure.

I do know that higher is better. :)

I'd also think a lot of controlling the sound is gonna come from the rest of the room....it's shape, dimensions and treatment.

Course...I could be just talkin out my ass in which case I'd stay up wind if I were you.
:D
 
I'm guessing (wildly) that a non-symmetrical slant would be better than a flat or symmetrically slanted roof.

Also, reflective floor (hard) and absorbing ceiling (soft) is the best combination.
 
you need to ask that here. http://www.johnlsayers.com/phpBB2/index.php
Click to expand...
Why?
I can.

The answer is...

1.The roof has nothing to do with reflections or the acoustics of the interior shell unless the interior shell has a very low Transmission loss. Usually, at least in residential construction, the roofs are splayed for two reasons. Water abatement and ease of spanning long distances by virtue of trussing. Since trussing requires a bottom chord, this "normally" results in a flat ceiling, although the use of Scissor trusses will allow an interior splayed ceiling. On the other hand, if a roof is built via rafters, then "usually", a ceiling JOIST is required to keep the outer walls from deflecting outward due to roofing weight. Again, this creates a flat ceiling..UNLESS, the rafters are actuall BEAMS. Which then allow a splayed ceiling plane too.
So..if you are planning any type of splayed ceiling, unless you have height to build a "decoupled" second leaf, the ceiling will be an integeral part of the roof. As such, structural transmission of sound to the roof is inherent. For those who are planning on a studio from the ground up, all these considerations must be addressed.

2. The roof is part of the exterior envelope, and as such needs to match the TL of the rest of the shell as much as possible. Unless of course it is 2' thick concrete or the walls are very high:D This also has to do with sound propagation to adjacent neighbors, your budget, needs and existing construction

3. If you are referring to a CEILING, this is part of the interior envelope, and is usually relatively much lighter in construction than an exterior. Thats not to say it shouldn't have a very high TL also.

4. If you ARE referring to a ceiling, then which room are you referring to? A Control Room or Live Room?

5. If you are referring to a CR, then the "school of thought" paradyme is at play. One team suggests the benifit of a sloped ceiling does not justify the expence, as there are only 2 reasons for it. One..to prevent flutter echo, and two, to reflect early reflections to the back wall to create a RFZ(reflection free zone). Both of which can be addressed by absorption, which is much cheaper. This view is a financial value as well as acoustics judgement as one of the best acousticians in the world is on this team.

The other teams view is... absorption removes "valuable" energy from the room, which they deem important enough to expend mucho bucks to implement by virtue of splaying the ceiling upwards from front to back at a minimum of 12 degrees. Sometimes this is done in two steps, although it takes a very experienced acoustician to calculate the reflection "ghost" images to correctly place these planes in relationship to engineering position in order to create an effective RFZ. Not only is the ceiling splayed, so are the side walls. This is done to direct EARLY REFLECTIONS in such a way they do not interfere with the direct sound from the monitors and to create a long TIME DELAY GAP. Most contemporary Studio designers are on this team.:D And sometimes, they will STILL use absorption above the engineering position regardless if the ceiling is splayed. And sometimes, they will build ENORMOUS bass traps there as well. Which makes me wonder why they splayed it in the first place.

Two things they don't want. At least untill some designer has enough clout to convince clients otherwise. :p

a. a ceiling sloped DOWNWARDS towards the rear wall from any point front to back.

b. A REVERSED cathedral type ceiling. This is called a "compression" ceiling which was the new "school of thought" in the late 70's. After a short lived period of celebrity status was enjoyed by the studio designer who initiated this school of thought, enough engineers discovered sonic anomolies that were attributed to this idea, and it fell out of vogue. Whch tells me a lot of this stuff is ambiguous and based on a given Studio Designers preferences...and reputation.:D Although, over time, proven design philosophys remain in use.

6. If you are referring to a Live Room, then other justifications come into play. First is ceiling HEIGHT. Since a microphone for a vocalist in a normal resididential room is within 30" of a FLAT ceiling, COMB FILTERING is the main concern. In this situation, absorption above the mic is the treatment dejour
for abatement. For those with the luxury of a higher FLAT ceiling, adustable absorption/diffusion panels are usually employed. For those who are fortunate enough to build from the ground up, or have an existing room with both a high and splayed ceiling, again, a combination of treatments is the norm. However, most PRO studios have a very high FLAT ceiling in the live room, as usually, these are commercial buildings with FLAT roofs.

So, to answer your question. It depends. On many factors.
 
So what yer sayin is to go with round vertical ceilings?
Click to expand...
Where did I mention "round"?:confused. And btw, how can you build a vertical roof?:D I believe that becomes a wall.:laughings:

No, what I'm saying is...whether to splay a ceiling depends on many factors, of which, "school of thought" opinion plays a role. And that role depends on who you believe.;)

If it were dependent on PURE SCIENCE, then it would indeed be either one or the other. :rolleyes:
 
Use a mansard style roof line (somewhat pitched and curved) and get rid of every equal and square corner in the room.

You need to break the waves and rid the possibility of multiple harmonics that square and equal corners create.

Think in terms of a B2 bomber with no right angles.

That's the key. Get rid of every 90 degree angle and your work is done.

I have done two very high security buildings at Lawrence Livermore Lab (among many other sound rooms, theaters, and the like) that others said were impossible to do. You could not stand the reflections in either areas. A huge difference now.
 
That's the key. Get rid of every 90 degree angle and your work is done.
Click to expand...
And what work would that be? Splaying walls/ceilings does not get rid of modal issues. It only makes them less predictable. So what are you referring to by "work"?
 
While it won't eliminate modal issues, it will deal with direct reflection problems. That could be a great thing depending on the goal.

Frank
 
It will rid direct reflections and the resultant multiple harmonics from those reflections.

Low frequency is the tough one since the wave is so long, but design the room correctly initially, and that issue is nearly put to bed.
 
GCalo said:
It will rid direct reflections and the resultant multiple harmonics from those reflections.

Low frequency is the tough one since the wave is so long, but design the room correctly initially, and that issue is nearly put to bed.
Click to expand...

True, but that takes some doing and some serious money. Definitely doable though.

Frank
 
"If I were a rich man"???

Not expensive as it is easy to do in the original design. Even a retrobuild is not tough.
 
Use a mansard style roof line (somewhat pitched and curved)
Click to expand...
I'm positive the personel at Lawrence Livermore Lab were delighted
with theirs.

I'm curious though. What does a mansard roof have to do with an interior envelope? Especially if the interior envelope is a room within a room TL strategy:confused: BTW phlopip, do you have a "significant other"? She might appreciate being considered as she may not like a mansard roof style. I know my wife would kill me if I made this sort of decision without consulting her.:D

Oh...and what do you mean by a "pent roof"? I've never heard that term before.

Low frequency is the tough one since the wave is so long, but design the room correctly initially, and that issue is nearly put to bed.
Click to expand...
Could you please explain what this so called "correct" room has that a room with splayed walls and or ceilings doesn't and how your roof concept deals with low frequency abatement?



Not expensive as it is easy to do in the original design.
Click to expand...

Exactly what is "not expensve and easy to do? :confused: You haven't explained anything yet.

Even a retrobuild is not tough.
Click to expand...

Perhaps you would be kind enough to explain this "not tough" design strategy/technique so typical home studio enthusiasts with a 9x11 bedroom studio in a 930sq' home can take advantage of it. I'm sure they will appreciate the "not expensive" aspect as well should they be in the planning stage.
 
Primary goal is to rid all the 90 degree angles. Those trap the harmonics and cause the multiple additional harmonics which destroy the clean signals.

Do whatever it takes to get rid of them.

As to ceiling, the ceiling style I mentioned is generally for new construction or for rebuilds. For existing rooms you can use angled foam blocks or you can sheet rock in a piece to rid the 90 degree angle. (see drawing).

If you are using an existing room, you can purchase angled foam to put along ceiling line, etc. to rid the corners and will also act as damping. This should not offend the lady of the house if the room is dedicated to your usage.

Ceiling design helps control all harmonics to rid the multiples. It is not just one factor;it is everything combined. The ceiling is a great place to start when building or remodeling. Look at all the 90 degree angles with respect to the room!

I missed "pent". Help me there.

Therefore a "correct" room has few right angles, few equal length walls, and negligible harmonic issues.

Search for acoustic materials, etc, and you will come up with a ton of info. Auralex is a good one. They seems to have everything you would need.

Hope this answers what you were asking. If not fire away.
 

Attachments

  • wall drawing.jpg
    wall drawing.jpg
    3.9 KB · Views: 296
That can do but a design such as that can cause some problems as well.

If you look at my drawing, turn it 45 degrees to right, you have effectively a mansard configuration for the corner which works extremely well for ceiling design. That is a more ideal way to go.
 
You must log in or register to reply here.
Back
Top