Low-Noise Basketball Backboard 1

[Athanatsius]

My kids love basketball and play in our cul-de-sac, but a neighbor has complained about the noise from the ball and backboard. I have found some low-noise foam-filled basketballs that bounce about like a real basketball, and now want to make a sound-dampening backboard that will produce very little noise. Any suggestions as to how to construct it?

 

[ivymike]

attach it to something farther down the street?

 

[IRstuff]

Can't you foam the backside of the backboard?

TTFN

 

[CESSNA1]

Athanatsius:

Make sure it is firmly attached to the pole or two poles. Then spray on automotve undercoating to the back of the backboard. If there is a space between the backboards then foam in between. The supporting pole(s) can also vibrate so you may want to use elastomeric mounts between the backboard and the pole(s). You may also want to add stiffeners to the backboard.

Regards
Dave

 

[Athanatsius]

Thanks for the great ideas! I placed a similar post on a sound studio acoustics forum and got some additional ideas, too. Here is the plan I am envisioning, so far:

1. Cutting the backbard from laminate treated plywood.
2. Gluing a rubberized or composite sheet to the front of it that wraps around the edges.
3. Screwing it to a stiffening frame of treated 2"x2"s, tucking the sheet under the frame.
4. Spraying the back of it with an automotive underhood spray.
5. Mounting it to the pole with elastomeric mounts.

Any other ideas, please let me know. Once I build it, I will let you know how well it works and will post a picture when I am done.

 

[CESSNA1]

Athanatsius: Let us know how it works, and whether you did anything else.

Regards
Dave

 

[spciesla]

Attach foam to neighbor, preferably to his ears!

 

[MikeHalloran]

Laminate rubber and then plywood over a thick steel backboard.



Mike Halloran
Pembroke Pines, FL, USA

 

[Dinosaur]

It seems to me there are two problems to quieting a backboard. The first problem is making the attachment to the structural support "rattle free". I think you may have to construct the backboard itself from something more substantial (e.g. very heavy) to further reduce the noise. Will your neighbor appreciate your efforts or will he continue to complain? Seems to me as long as the kids are not out before eight in the morning and are in at eight in the evening, you gotta expect kids to be kids. Good Luck

 

[Rob45]

First, I want to say you are to be commended for your concern for your neighbors; not everyone is so considerate.

I'd suggest that what you need is a backboard that doesn't vibrate and hence won't radiate noise. A sheet of lead would be ideal, but might be hard to hold up, so I'd suggest this as an alternative: you can make the backboard from a sheet of "dB-Ply" plywood from Greenwood Forest Products (Portland, Or.) It is a plywood that incorporates a viscous damping layer.
Others have suggested foam or other materials sprayed to the backside of the backboard and while these will slightly reduce the noise, they are not as effective as you might wish.
What you want is a means of applying a constrained-layer damper to the backside of the backboard: one way of doing this would be to apply a layer of 3M trim cement or equivalent to the backside, and use it to mount a layer of sheetmetal or plywood. Then vibrations in the backboard are dissipated in trying to shear the adhesive.

Then you'll only have to deal with the kids' shouts when they score the winning basket...

 

[GregLocock]

Incidentally a rule of tumb is that the damping layer should be 3/4 of the way through the thickness of the board, that is the construction should be

3/16" ply
damping layer
5/8" ply


roughly

This will be far more effective than a sprayed-on layer of goop.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Athanatsius]

Thanks for the excellent advice. GregLocock, in the example you provide above, how thick should the damping layer be? If 3/4 of the way through, then 2 7/16" ? Or do you mean that the layer should begin at 3/4 of the depth?

 

[Tmoose]

What does the problem "sound" like?
Sharp thump? The "tunk" or slap the basketball makes itself when bounced on concrete?
Hollow ringing of the steel pole?
Once the pole is stiff and full of expanding foam, and
Damping and stiffness have been applied liberally to reduce the flexing and ringing of the backboard, (and perhaps noticeably influence the ball's rebound) but in the limit you're left with a rigid body motion, which makes a fine loudspeaker.
When all else is optimized Howzabout making backboard perforated with holes sized for the frequencies of interest. The purpose is partly to equalize the pressure front and rear. Mighty effective in making quiet belt guards, etc.

 

[electricpete]

I'm no sound expert... but I did have a cheap basketball hoop in my backyard at last home. I think the main source of noise was that the backboard is a thin sheet of metal that acts like the head of a drum. Thicker sheet with something behind as recommended above seems better.

Another variable you might explore is the inflation pressure of the basketball.

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[GregLocock]

I'd use 1/16" of goop in that example, to start with. There is a way of trying to calculate it, but any sensible engineer would just suck it and see!

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Wicsteve]

Try a layer of 5/8 inch cement board (similar to sheet rock) laminated to plywood