MIL-STD-810 Test Method 515.6 Acoustic Noise

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Jim Shaw, EVP of Engineering at Crystal Group, discusses MIL-STD-810 Method 515.6 Testing.

Video Transcript: Episode 83 – “MIL-STD-810 Test Method 515.6 Acoustic Noise”

Hi, Jim Shaw here from Crystal Group.  Wanted to spend a moment just talking about MIL-STD-810.  And today we are focused on acoustic noise, which is Method 515.  And what’s this all about? Well surprisingly enough this is a lot like vibration, Method 514 but acoustic noise is really how a product that you’re building responds to a noisy environment.  It could be a someplace that mounted to a jet engine.  It could be external stores on an aircraft.

It could be next to a rocket motor on a missile.  One of things that you’re testing here are pressure waves.  And these waves can be from 5 kilopascals to 87 kilopascals.  So it’s actually quite a bit of energy in those areas that you’re looking at where its noisy.  And those pressure waves induce essentially vibration.  And that vibration can impact your equipment.  The frequencies of that vibration are anywhere from 10 hertz to really 10 kilohertz.  There’s a lot of energy in that area.

The things that you are looking for in acoustic noise really is how does your equipment stand up to that kind of noise.  You’re looking for that same kind of things that you’re looking for in vibration.  Is there fatigue, is there chaffing of wires, are you breaking solder joints, are you damaging any of the equipment materials or any of the structure? Ironically it’s a lot like the vibrations spec, it’s just being applied by rather than kinetic motion from a variety of different input mechanisms you’re actually driving that energy and putting it into the system through sound waves.  So that’s in effect what you’re doing when you’re doing acoustic testing.

There are three kinds of acoustical tests.  There is diffuse acoustic noise.  And that’s essentially the equivalent of mounting your external stores on an aircraft.  So what kind of vibration would that create? Then there’s also grazing incidence noise.  That’s essentially equipment that’s located in a ducted area, that would have a very loud type of an environment, very noisy environment.  And then the last one really is cavity resonance.  You get into that sometimes when you are in a let’s say a bomb door area or a storage area where doors open and then you get kind a buffeting resonance type of an energy.  And that can be quite destructive also.

This test is a Life test.  So you’re really testing endurance of the product.  As every other method in MIL-STD-810 each one of these methods has to be tailored, each procedure tailored to the specific application.  Again you’re looking for how does the equipment stand up to that type of exposure to those energy levels.  So that’s in essence what you’re trying to test for with this particular acoustic test.  It’s a lot like the vibration types of testing that we do.  That’s what we are looking for.  I hope that’s helpful.  Thanks a lot.

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