Vibrations, audio components, and sound

Blizzard said:

What do you recommend? This one looks pretty cool. Wider frequency range as well. Can connect to mobile devices.

http://digiducer.com/

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That does look more capable when coupled with something like the spectraplus software.

However, first question you have to ask is what do I want to measure for what reason?

For example, that digiducer transducer is pretty large and (relative) high mass. If you attach that to something of (relative) low mass you will significantly affect its vibration characteristics. For example, attaching that transducer to the thin folded steel lid of an amplifier or cd player or similar would not be a good idea.

Blizzard said:

One of these unit's are on my "to buy" list.


http://www.dytran.com/Model-5346A1-...Vibration-Sensor-Analysis-Software-P3045.aspx

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These and the other device posted are very cool toys. I've been wanting to get one myself for quite a while to play with. Personally I would love to know where JA of Stereophile gets those "plastic tape" accelerometers from he uses when measuring resonant modes on speaker cabinets. I think one of the tape style attachments in combo with one of the devices posted here would be real fun to play with.

Not a cheap toy by any means but I could see myself staying occupied with it for quite some time

BE718 said:

That does look more capable when coupled with something like the spectraplus software.

However, first question you have to ask is what do I want to measure for what reason?

For example, that digiducer transducer is pretty large and (relative) high mass. If you attach that to something of (relative) low mass you will significantly affect its vibration characteristics. For example, attaching that transducer to the thin folded steel lid of an amplifier or cd player or similar would not be a good idea.

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Mostly speakers and audio electronic enclosures. I want to optimize the vibration dampening characteristics to ensure vibration from speakers isn't transferred into the electronic components. Especially the clocks in the DAC. According to the guy who measures the phase noise of my clocks, even the slightest bit of air movement around a clock causes spikes in the phase noise. He knows because he watches clock phase noise plot in real time while connected to his $100000 machine. Even when he blows a slight breeze over the clock, the phase noise spikes. So I trust him that vibration isolation is important when it comes to DAC clocks.

Here's one that is 3 Axis and measures up to 2.7kHz on X & Y with Z maxing out at 600HZ. Pretty wide bandwidth but its large and you'll need to bring your soldering iron to use it unfortunately

http://www.nxp.com/products/sensors...s:FXLN83xxQ?fsrch=1&sr=1&pageNum=1#targetApps

I've been playing with the built-in cheap i-Phone 3 Axis accelerometer for quite some time. I use it for 1000ft view when measuring equipment rack and component chassis vibration while experimenting with different isolation feet..etc

I would much prefer to have one of these other devices listed here though.

cjf said:

These and the other device posted are very cool toys. I've been wanting to get one myself for quite a while to play with. Personally I would love to know where JA of Stereophile gets those "plastic tape" accelerometers from he uses when measuring resonant modes on speaker cabinets. I think one of the tape style attachments in combo with one of the devices posted here would be real fun to play with.

Not a cheap toy by any means but I could see myself staying occupied with it for quite some time

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He uses PVDF piezoelectric sensors. They are pretty cheap to buy actually. Here is a nice article on them: https://www.sparkfun.com/datasheets/Sensors/Flex/MSI-techman.pdf. And sample from their web site: https://www.sparkfun.com/products/9197

amirm said:

He uses PVDF piezoelectric sensors. They are pretty cheap to buy actually.

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Thanks Amirm, I've been passively searching for this contraption for a few years now, embarrassingly

Now I just need to figure out how to use it in combination with a similar setup as posted earlier in this thread with a USB/Software kit like posted by Blizzard earlier in this thread. Back to my cave I go to do some more reading

amirm said:

He uses PVDF piezoelectric sensors. They are pretty cheap to buy actually. Here is a nice article on them: https://www.sparkfun.com/datasheets/Sensors/Flex/MSI-techman.pdf. And sample from their web site: https://www.sparkfun.com/products/9197

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Just be aware of a few things with these accels. First you will need a charge amplifier and care will need to be taken with cabling and the mounting. Also the resonant frequency of the transducer is at a relatively very low frequency. This could be very problematic. See the graph in the data sheet.

Actually considering all that I would say this type should be avoided.

Blizzard said:

Mostly speakers and audio electronic enclosures. I want to optimize the vibration dampening characteristics to ensure vibration from speakers isn't transferred into the electronic components. Especially the clocks in the DAC. According to the guy who measures the phase noise of my clocks, even the slightest bit of air movement around a clock causes spikes in the phase noise. He knows because he watches clock phase noise plot in real time while connected to his $100000 machine. Even when he blows a slight breeze over the clock, the phase noise spikes. So I trust him that vibration isolation is important when it comes to DAC clocks.

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Yes vibration can cause phase noise in clocks, but you you need to put this in perspective and ascertain if it's actually causing a problem in the DAC output.

To evaluate this properly you will need a shaker table .

Equipment cases do indeed vibrate due to acoustically induced vibration and one of the things I will show is the resonance in my Tag processors lid. However much I vibrated the amp with in room loud music, tones and pink noise, I could find any evidence of issues in the output. Note it's clock crystals are surrounded by soft rubber.

As I alluded to previously if you want to measure the vibration for example of the clock crystal you will need a transducer of appropriately low mass. Something appropriate will have low output levels and more issues with noise and low frequency response.

Not trying to put anyone off but there are pitfalls and the instrumentation (of decent quality and capability) ain't cheap


Some accel suppliers

Bruel & kjaer
Endevco
Wilcoxon