Playing in a Garage (acoustics & some old cars)

[abstamaria]

When I started to address the acoustic issues of the garage, I thought I should borrow some carpets from another room and cover the walls with egg cartons.

What I learned since is that carpets and egg cartons will absorb only the higher frequencies, which have very short sound waves, and not affect the lower frequencies. This is a diagram that shows the effect of egg cartons. The lower frequencies (notes) will sound (and reverberate and be reinforced) as before, but there will be a pronounced dip in certain of the higher frequencies. What one wants is equal absorption, and for that purpose size (or more accurately the depth and density of the absorbing material) matters.

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It therefore turned out that the simplistic carpet-and-egg-carton treatment I envisioned would not be adequate. Selling my old car, painful for me, did free up the garage space and allowed a small budget that I would not have otherwise had. I bought a nice guitar and some gear but did not expect acoustic treatment to be so complicated. I was lucky though in that one of my old-car friends was in the business of sound treatment and would help for free.

[GoldenStreet]

Hi Andy

There's a thread here - viewtopic.php?f=11&t=3788&hilit=shadows+map -
that leads to this link - http://maps.google.com/maps/ms?ie=UTF8& ... 4f363e86e8 - that has some Shadows related places plotted

Roger

Am I right in thinking that Hank lived in Totteridge at some point in the 60s?

Bill

[RogerCook]

Totteridge Lane as far as I know

[abstamaria]

Just to report that that the band came over today to play and that the just-completed acoustic treatment had noticeable, positive impact on the band’s sound. The band was quite surprised. Each instrument came through the mix very clearly for all of us, including the drummer. In retrospect, we were getting a very confused sound before acoustic treatment, but had just accepted that. Now we are getting a good clean sound. We are all quite pleased.

I replaced the open steel rack with the low shelf shown here. The acoustic panels can be seen in the photo, too.



Andy

[abstamaria]

Before we decided on how to treat the room, my friend in the acoustic treatment industry came over and brought a machine that generates its own noise and measures room modes. After some time, he concluded that the room emphasizes 250 Hz and, to a lesser degree, multiples of that frequency. That seems closer to a B rather than an E, but that’s what the measurements indicate.

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Later, he consulted his colleague, also a friend who mine who studied acoustic engineering in the US, who recommended thick acoustic panels on the ceiling. I am reluctant to do that as the ceiling is already so low! That is in addition to the wall panels shown in the earlier photo.

Andy

[abstamaria]

The compromise solution was to install acoustic panels (the white rectangular sections) on the ceilings, with thicker sections above the drum kit, as shown here. As seen in the earlier photo, we also installed acoustic panels, covered in a dark grey cloth, on some walls. (I like to say that the white, insulated tubing shown on the ceiling in the photo are frequency-specific absorbers, but they are actually airconditioning conduit. The workshop/"studio" is a utility room, almost a basement.)



The idea is not to completely dampen ceilings or walls with acoustic foam, but to leave several sections bare and reflective, to preserve a natural sound.

The panels we installed are made of very dense foam (rockwool is a good substitute), so should be easy and inexpensive to replicate on a DIY basis. I was lucky in that another friend manufactures acoustic panels and other devices for concert halls, churches, recording and audiophile studios, and the occasional rock concert (he did the treatment for the recent Lady Gaga concert here; he says her sound engineers came with specifications for the treatment they needed and were very meticulous). His crew made and installed the panels for me at a very reasonable cost.

Here is a close-up of a wall panel.



I am posting all this in the hope that it will be useful to some in the future!

Regards,

Andy

[Didier]

Hi Andy,

Obviously, you are already well above the average "garage band" !

Didier

[abstamaria]

Thanks, Didier. I didn't intend it to be that. I thought it would be a simple job of moving out the car and workshop things. The sound seemed all right before, but it is only in comparison to what we are hearing now that I realize we were getting a confused sound before.

My best,

Andy

[abstamaria]

One of the questions I posted a year ago was where to place a drummer in a practice studio. The problem was that the drummer could not hear the guitars over the sound of his drums.
I thought that part of the problem was the location, which in the case of our rectangular “studio” placed the drums at one far end and the amplifiers in the middle. I thought also that the sound from the cymbals, snare, etc, bounced around quite a bit, adding to the din the drummer was hearing.

Although not recommended by the acoustics fellow, I thought it would help to place the drum kit on a thick rubber mat, to minimize reflections off the floor and, as an incidental benefit, keep the drums and hi-hat from slipping. I did some reading on the Web, and there are several recommendations for rubber “isolation” mats, principally to reduce sound transmission through the floor (and avoid infuriating neighbors). The mats are supposed to improve the drum kit’s’ sound, too. One of the commercial products is Auralex, which has this to say:

“The HoverDeck Sound Isolation Riser is specifically engineered to reduce coloration from floor resonance by decoupling the drum kit, resulting in a "tighter", more "pure" sound for both studio and FOH.”

There were thick, interlocking rubber mats at the supermarket hardware section, so I bought these as an inexpensive solution.

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I can’t isolate the effect of these mats, as the acoustic panels are now on the ceilings and walls (and the drummer has been using light, bundled-stick drumsticks), but the drummer said at last weekend’s session that he can hear everything clearly now. And so can we. Maybe the mats help.

Andy

[abstamaria]

Room acoustics is a black art to me, but I am trying to set down here the little I learned and in the process perhaps make the subject clearer to myself.

The culprits are echoes and excess ambience, resulting in a confused sound and peaks and valleys in certain notes depending on where one is in the room. Low frequencies are often a problem, with large volume variations, especially in smaller rooms, caused by bass waves bouncing off the wall behind the listener. Nulls as deep as 30 dB are not only common, but typical.

The problem seems worst with a live band in a room with hard walls, exactly my situation.

One solution offered on the web is bass traps, which absorb low frequencies in the hope of providing a much flatter, tighter, and more even response for the bass amp and the kick drum. One of the proponents of bass traps, the US company that sells Realtraps, says it's not possible to have too much low frequency absorption. They have a very informative site with interesting articles on acoustics. Here is a link (I have no connection with them):

http://www.realtraps.com/art_basics.htm

Some articles on the web state the reverse and say that too many bass traps will suck the sound out of a room, so it's confusing.

The Realtraps seem an interesting solution but are quite expensive to buy and to ship, particularly as I am so far away. Perhaps I can have them made locally.

Andy