MadSci Network: Physics

Re: How loud is 39dB?

Date: Thu Dec 12 19:14:19 2002
Posted By: Aurelio Ramos, Grad student, Computer Engineering
Area of science: Physics
ID: 1039503343.Ph

In my personal opinion 39 db is "distractingly loud".

I can assure you at that distance the noise will be clearly audible, if 
not somewhat anoying, unless you play your movies at very loud levels. I 
speak from experience, since I went thru a lot of trouble to quiet my PC 
down to about 25 dB (A weighted).

25 dB is the average background noise level of relatively quiet home and 
office locations. Your projector is nearly 15 dB above that level, a 
noticeable difference.

39 dB would be similar to the sound level of soft conversation at about 8 
feet or so, except that being broadband in nature (as opposed to a 
specific pitch), it would not be as distracting as a nearby conversation. 
Another example at nearly that noise level would be a household fan set 
to medium low speed at about 6 feet, or sitting inside a compact car 
(honda civic, toyota tercel, etc) with the windows closed while the 
engine is idling, while the car is parked in a quiet place.

However, At 2 feet from your head, I think that noise level will be 
simply too loud for most people's tastes. Notice that most manufacturers 
report noise level at an industry standard 6 feet's distance (except of 
course car manufacturers, who report noise level from the driver's head 
position). And the closer you get, the louder it gets. Try to imagine a 
household fan running at medium low speed 2 feet away from your head and 
you get the idea. It's not unbearable, but certainly distracting.

Depending on the projector itself and on the room, you may be able to 
place it higher up to distance it from your own ears, possibly at the 
expense of image quality (since the image could get distorted by changing 
the angle of projection) But as far as sound, the closer you can place 
this projector to the ceiling, the better.

If mounting the projector far is not enough for your personal taste, and 
if the wall behind your living room leads to another room in the house, 
another idea would be to make a hole in the wall, mount a double pane 
glass window, and install the projector in the opposite room. Make sure 
there is adequate, clean ventilation in the projector room to keep it 
running cool.

Good luck!


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