standard methods for sound damping

Hey!
We developed a material for reducing the sound level. the material, in the form of a sheet, will be kept in between two metallic sheets.We would like to know how much sound it dampness. As we have to supply it to some automotive industries, we would like to have the standard method to determine the amount of sound it dampened. can anybody tell me the standard procedure to do it? or any standards available on it.

thanks
pmsrao

 

[GregLocock]

There are a few industry standard methods.

The real standard is to measure the sound transmission loss (STL) in an STL suite. The SAE probably has a standard for this.

Another standard is the use of an APAMAT machine that throws ball bearings at a sheet of treated steel, and measures the resulting noise.

However, neither of these gives any more than a rough guide to the performance of your system (a constrained layer damping material) in a specific application.

Why not ask your customers what tests they'd like done? Cheers

Greg Locock

 

[Rob45]

For sound transmission-loss, the "standard" method would be the ASTM E90; other customers such as Ford and General Motors have their own variations on this basic test.
For a constrained-layer damping material, though, perhaps what you want to do is to measure the loss factor at various frequencies, i.e., the bandwidth at the half-power points divided by the resonant frequency.

 

This particular application dooesn't typically figure into STL for Auto, as the double layer will never completely cover say the floor pan. This system called constrained layer damping is used to increase mass, stiffness, and convert dynamic energy into heat in the areas such as footwells and rear wheelhouse. The proper
test for this is the Oberst bar method. Not sure of the standard for the test but it ends up getting post processed with ASTM E768. Pranab Saha of Kolano & Saha is your best bet for an expert to contact in this arena.

Hope this helps,

Eric

 

[Rob45]

Well, since Rao said "we would like to have the standard method to determine the amount of sound it dampened," I assumed he was referring to sound attenuation, not vibration damping (and not, of course, to getting sound wet).
Thus the reference to the STL testing.
Mr. Saha would refer you to an Oberst Beam test, but this doesn't necessarily tell you what you want to know if for example, you're trying to reduce sound transmission through a firewall.