Reducing echo in the big garage workshop
I have been working on setting up my big garage workshop
so that it's also a good space for making videos. Early last year, I made some
tarp clips for hanging canvas drop cloths
(meant to use when painting) to help absorb the echo. I hung some, and
they made a difference. But then I decided I should paint the walls and ceiling
before hanging the drop cloths. Painting that shop stretched out over a long time.
Now that I have the shop painted, it's time to tackle the echo problem again.
As usual, I'm using my motorized scaffold to work on the walls and ceiling.
I'm using some fairly heavy canvas drop cloths and attaching the
tarp clips along the edges...
... then screwing the tarp clips to the ceiling. For a 9'x12' (2.6 x 3.5 meter) drop cloth,
three along each long edge appears to be enough.
I hung two 9'x12' (2.6x3.5 meters) drop cloths on the ceiling, and one drop cloth on each of
the opposite walls. Just the four drop cloths made surprisingly much difference, even though
I don't have any sound dampening material behind the drop cloths.
Judging how bad the echo is is very subjective, so I made audio recordings at various points in the work to later review.
I also bought three 9'x12' disposable drop cloths, which were much cheaper than the
canvas ones. I hung these along another wall, but reviewing test video and sound
after hanging them, they don't appear to have helped any.
I guess they are just too light to make much difference. They only cost $5 each,
compared to $25 for three canvas ones, so in terms of (not) bang for the buck
they weren't any worse.
So I hung the three disposable drop cloths in front of each other
in the back corner and hung two more of the canvas ones in their place.
Then I hung another drop cloth on the ceiling. This one would get hit by
the garage door when it's opened, so I also attached it in the middle.
With all the fabric now hung, it makes a world of a difference. Enough so that I can talk to the camera from two meters away and still have good sound.
I'm sure people will tell me I could just use a clip on microphone, but the whole idea of all this is that I won't have to use one. Besides, I really dislike the sound in videos done with clip on microphones in echoy rooms.
As I was editing the video, I looked at the sound graphs from me clapping.
The upper (purple) one is of me clapping in the shop when it was still
mostly empty, the lower one is now. The vertical divisions
are 500 milliseconds. So originally, it took well over half a second for
the reverberations to die down, and now it takes about 0.2 seconds.
It also makes the space quieter overall. I originally found the fan that I use to blow air into the back of the stove annoyingly loud, but now it's ok. Before, I heard not just the fan, but also all the reverbrerations of that sound.
Getting rid of reverberations is more challenging in a big space. As the sound bounces back and forth, a certain fraction is lost on every bounce, but in a small space the sound has to bounce back and forth a lot more often in the same amount of time, so it decays faster.
What the shop sounded like over the last year:
January 2014 - Mostly empty: Workbench video
February 2014 - Some stuff moved in: Scaffold build
April 2014 - Two canvases hung before painting: Wifi booster dish
September 2014 - Chaos in the shop: Wasp sucking machine
See also:
Making sound absorbing panels
Wooden tarp clips
Building a scaffold
Wifi antenna
About my camerasand making videos
To my Woodworking website.
