John Sayers' Recording Studio Design Forum Archive

I am placing sound proofing panels above the mixing position. Is that correct? Should I angle it? It will be 2 panels covering only 1.5 X 1.8 meters rectangle in total.

What kind in general are the panels meant to be above the mixing position. Does it need to absorb bass or just diffuse.

I am also seeking answers to my other post.

Yoga,

> I am placing sound proofing panels above the mixing position. Is that correct? <

No, you want to put absorbing panels on the ceiling above the mix position.

> Should I angle it? It will be 2 panels covering only 1.5 X 1.8 meters rectangle in total. <

No need to angle it.

> Does it need to absorb bass or just diffuse. <

Neither. You want to absorb mid and high frequencies so they don't give "eary reflections." For more on this see the sidebar Creating an RFZ in my Acoustics FAQ:

www.ethanwiner.com/acoustics.html

--Ethan

Are acousitc tiles or foams sound proofing materials or sound absorbers. Can acoustic foam be used in the same way as rigid fibreglass is used. Example, when making your bass traps, instead of using fibreglass, use acoustic tiles or foam of equivalent rating. Does fibreglass and acoustic foam act in the same manner?

yoga,

> Are acousitc tiles or foams sound proofing materials or sound absorbers. <

Absorbers. This, and all your other questions, are answered in my Acoustics FAQ I linked above. I know it's a lot to read, but I put it into one place to make it as easy for you as possible. And when you're done - even if you have to read it twice - you'll know a lot about acoustic treatment.

--Ethan

yoga,

yoga wrote:Can acoustic foam be used in the same way as rigid fibreglass is used. Example, when making your bass traps, instead of using fibreglass, use acoustic tiles or foam of equivalent rating.

Yes, that would work fine.

Does fibreglass and acoustic foam act in the same manner?

If you mean do they absorb sound the same way, the answer is more or less yes. If you mean do they absorb the same amount of sound, the answer is no. Generally, the thickness of (sculpted) foam to (flat) fiber is roughly 2:1 for the same performance. But that can vary widely since fiber tends to be available in a wide range of densities, whereas good acoustical foam tends to be around the 2 lb/ft³ range of density.

In other words, for the same general performance as a flat piece of 2" fiber, you will need about 4" of acoustical foam.

There are other factors to consider, but the above is a good general overview. Also worth noting are:

• Air gaps behind any absorber help with low frequency performance.

• Sculpted foam has better off-axis performance than flat fiber panels. This is more important in the high frequencies than the lows. As you approach what's called "grazing incidence" on an acoustical absorber, absorption decreases.* This is quite noticeable for a flat fiber panel, but not nearly so signficant for sculpted foam panels. This can sometimes result in a "foam room" sounding more consistent than a "fiber room," all other factors being equal.

*To steal an analogy from a good friend of mine, think of "grazing incidence" being like skipping a rock across a pond. If you drop the rock in the pond, this is like "normal incidence" - sound hitting a panel straight on does not come back just like the rock doesn't bounce off the surface of the (not frozen ) water. Skipping the rock can result in it bouncing off the surface. Get the right angle and you can skip it quite a bit, just like if you hit a flat absorber at the right angle, the sound will bounce right off.