We would appreciate comments on our experiment.

[Andred]

Hi all, we are doing an experiment using sound barriers. The experiment is that a sound barrier is placed in between a highway and a service road. There is a town next to the servive road, on a hill. The experiment is to see wat barrier, if any will work the best in this senario. this post holds our Materials and Procedure.

MATERIALS:
• Large cardboard box
• Topsoil
• Bedrock (if scale goes that deep)
• Grass
• Wood sound wall to scale
• Cement sound wall to scale
• Filler soil and grass
• Tape/CD recorder and player
• Audometer
• Small plants
• Map of Roslyn
PROCEDURE:
1. Research to give yourself a basic understanding of sound physics
2. Gather materials
3. Put the map of Roslyn together
4. Build an approximate model in a cardboard box. Use topsoil as the base for your model and the grass/filler soil to hold it in place. Create your various sound walls and place them the correct distance away from the top of your topsoil hill.
5. record sound at highway, or create an approximate sound
6. Place sound source at highway on model and receiver at designated area
7. Play sound with no barrier (control)
8. Record dB at receiver
9. Repeat steps 4-6 replacing the empty space with a sound barrier until all barriers are tested
10. Run second and third trials
11. Record data
12. Conclude

[deleted-2574]

Hi Andred!

I don't have any specific comments on your procedure, except that it is seems pretty thorough!

You might try feeding "how do you evaluate sound barriers?" to answers.com, and see if you get any more ideas.

[geoffbruton]

Hi Andred,

This sounds like an excellent project! Although this is not in my field, your general outline looks very well put together. One of my concerns, however, is that you may not find a sufficient difference in noise reduction in your scale model, since you are planning on using an actual recording (dB level) of a real highway.

Consider the fact that in a real-life scenario, the actual noise levels produced by highway traffic are reduced by the introduction of a, say 20 feet high wall. In your experiment, it looks as though you are planning on using an actual dB recording with a *scale* model. I'm am not sure if you will be able to measure anything truly meaningful...

What have you been able to uncover through your research with regards to how noise levels increase (or decrease) with regards to the dB units? Would it be feasible to reduce the sound level in proportion to the scale in your scale map? Just a thought!

Hopefully someone else on this list may be able to give you some suggestions in this regard, and let us all know if this would actually be an issue.

Good luck and please keep us informed of your progress.

Geoff.

[deleted-71495]

Hello,

I would like to make two points here:

(1) I think your procedure should also control the environment of the scale model. Remember that sound gets reflected by objects like walls, etc. So I would not conduct the scale experiment indoors, unless you can find a soundproof room (with egg-carton shaped foam covering the walls or similar). Outdoors, on the other hand, your receiver is more likely to pick up other noise which will add to the dB you measure. But you can probably find a reasonably quiet place, measure the baseline dB, and then what is added by your noise source.

(2) I too am in doubt whether the scale model is going to give you meaningful results. But you can figure this out by running some trial experiments beforehand. For example, why don't you use a setup where the sound barrier is much bigger in dimension than your noise source (speaker, hammer, radio.. whatever is handy) and see what kind of readings you get depending on (i) distance of noise source to barrier (ii) distance of receiver to barrier (iii) some variations of the two, including displacing source or receiver closer to the barrier's edge while maintaining the distance. That should help you estimate what kind of scale factor is useful for you. And it may already be the data you were looking for in the first place...

[deleted-71360]

A few thoughts, some may be useful to you.

To make meaningful sound measurements, you need to be in a quiet place. Really quiet. Miles out in the country away from anyone or anything else. If you can hear anything more than your own breathing, you are in a noisy spot.

Some recent news stories on sound walls stated that the people near them liked the lower sound levels while people some distance away from them reported louder sounds. My suspicion is that the nearby people benefited from the sound block in the near-field. The distant people probably were suffering from reflected sound from the opposite side of the road and the noise they heard was coming over the near-side wall.

A smooth surface will give a directional reflection while a rough surface will be more dispursive. Smooth and rough are related to wavelength, which are on the order of inches to feet.

Robert Reavis

[Andred]

Hi again. Thanks for your comments. We too are trying to figure out the issue of scale. As to doing the experiment outside, it is winter in NY. therefor, our readings would be affected. We hope to block some outside sources with our cardboard box.

Sorry for any spelling mistakes, my keyboard isn't working well.