Sound/Vibration Measuring Equipment 3

[arale07]

i'm new in the field. my company has two sounds chambers in two different locations. we do a lot of testing in both rooms. apparently test results from the two chambers for the same product sample differ up to a few dB's. what equipment would be approriate to measure the sound/vibration difference between the two chambers?

thanks!

 

[MotorVib]

There will always be a little differents between test stands. You will need define what is needed for the product, is it a coustmer or is it just a generial system check.

Take a good look at the background noise it can tell you how good your test stand. 3ed shift and Saterdays are good times to checks the test stands.

Chris

"In this house, we obey the laws of thermodynamics." Homer Simpson

 

[arale07]

Thanks Chris.

it's a new product in development. engineering is trying to get it below 62 dB. right now im getting borderline results at the engineering facility. and it apparently measures louder in the production facility sound chamber. if the ambient dB is lower than 40dB at both facilities, and im using the same equipments(moved from one facility to the other), the only difference in two tests performed is the chambers, where could the difference of the result come from? im lost.

 

[FeX32]

My first thought was the same as MotorVib but since you indicate the ambient dB to be similar then maybe the room/facility change changes the way the surroundings attenuate the sound from your system. Are the test stands in each situation identical?
If they are not identical then there is your problem.

good luck,





Fe

 

[MotorVib]

One other thing check the operator and see how they are testing. It might be something as simple are mic location.

Also what how the test stande is isolated?

Chris

"In this house, we obey the laws of thermodynamics." Homer Simpson

 

[GregLocock]

Look in this forum for a thread on testing semi anechic chambers. Apply the same testing to your two rooms.

Cheers

Greg Locock

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

 

[arale07]

the unit is bolted to a standing rack in the center of the room. there's a dummy torso with ears (2 mic's) left and right, below the test unit. 3rd mic is 2 inches above the unit, 4th is set to a distance away. one accelerometer on each side of the unit. A PC station is positioned in the corner of the room. All data is recorded with Bruel&Kjaer.

 

[GregLocock]

Ah OK you are testing some sort of telecoms gear or something. Another thing you can do is called a gage R&R,

http://en.wikipedia.org/wiki/Gage_R&R

, you can use it to characterise the statistical difference between the two facilities.

the chances are that he differences are due to the frequency response of the two rooms, if the difference is repeatable, so quoting single dB figures isn't much help.

Cheers

Greg Locock

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

 

[SomptingGuy]

How is the rack treated? Is it foam-wrapped?

- Steve