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Author Topic: 5D Mark III sensor cleaning noise (squeaks)  (Read 8910 times)

tron

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #30 on: October 31, 2012, 07:04:30 PM »
I'm now a bit worried that I've never heard or felt anything from my 7D during sensor cleaning.  :-\
Maybe because it doesn't work?   ;D
Seriously now I haven't noticed anything on my 5DMkII and 5DMkIII. They must be broken too...  ;D

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #30 on: October 31, 2012, 07:04:30 PM »

dlleno

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #31 on: October 31, 2012, 07:20:27 PM »
Dude Mt. Spokane thats no good.  I've got industrial noise and age related losses that frustrate my wife,  but nothing like you or rush limbaugh.  these outside-the-box methods are awesome and still emerging, to be sure ,and I certainly hope you are able to find some relief or improvement! 

@ Tron/AdamJ  lol forgive my reversion back to the technical -- I'd say that if you can't hear it, and you're hearing is ok/normal for your age, , then that is good!  Best case is that a teen-aged girl can't hear the sensor cleaning routine :D  then you know that no parasitic resonances are happening in the camera!   


TAF

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #32 on: October 31, 2012, 10:19:27 PM »
I just took some measurements, and my 5D3 sensor cleaning 'sound' is a series of two smooth frequency sweeps from 100 kHz up to about 125 kHz and back down.

So I would conclude you are hearing some structure in the camera vibrating, and not the actual signal.

indeed, given this data,  it is probably sympathetic resonance.  so the sweeps themselves -- is this a single tone sweep or what is the bandwidth of the signal that sweeps through 100KHz to 125KHz?  I take it you were measuring with a wide band audio spectrum analyzer, measuring actual acoustic energy? 


Yes, actual acoustic energy.

I am using a device specifically intended for detecting ultrasonic emissions, the Wildlife Acoustics EM-3:

http://www.wildlifeacoustics.com/products/ultrasonic-monitoring/em3

I'm still learning to use the instrument, so I cannot yet ascertain the purity of the sweeping tone.  It is fairly narrow on the spectrum display (which is very small), but until I can expand the range (or more correctly reduce the bandwidth so as to enlarge the displayed signal), I can't answer that.

I will post more when I get there.


TAF

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #33 on: October 31, 2012, 10:35:52 PM »
People can generally not hear ultrasonic tones, but they can dectect pulse trains at much higher than ultrasonic frequencies.  They sound like a chirp.


In the case of the Dukane pinger, you don't even need to hold it against the bone behind your ear to hear the once per second tick; it sound like a fairly loud clock.  Nothing special to that, the square wave pulse is obvious, and I suspect it is the end diaphragm of the device popping.

What I find interesting is that once you do put it against the bone behind your ear, and if you listen really carefully in a quiet room, you will start hearing the actual tone that comprises the pulse.  Imagine the highest pitch squeak you can, and then picture it getting higher in pitch still.  That's what it sound like.  It is a very odd experience.

This doesn't really surprise me, though.  The human ear is a very efficient acoustic filter, optimized for the frequencies we're supposed to hear.  It does a pretty decent job of reducing the 'out of band' signals that we're not really intending to listen for (the text book "Fundamentals of Acoustics" covers the math pretty well; my copy is at the office so I'll post the authors name tomorrow night).  But when you bypass the filter and put the input directly into the detector, finding that the little cilia in there vibrate at a much higher frequency than expected isn't shocking to me.

I have a few transducers that will operate out well past 50 kHz.  I'll have to try a few sine waves (no impulse to confuse things) and see what I can hear.  My cats may not like the experiment (the always sit outside the door to the workshop and meow when I play with ultrasonics), but I think I can confuse them for a few minutes for science.


dlleno

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #34 on: November 01, 2012, 07:18:54 PM »
lol nice work TAF I hope your cats survive the experiment :D   indeed,  bypassing the natural low pass filter of the ear is comparitively uncharted waters.  Here's hoping something useful appears in time for Mt. Spokane!  :D

TAF

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #35 on: November 03, 2012, 06:35:39 PM »
Follow-up:

1. The text book authors are Kinsler and Frey (and two other guys who I have forgotten)

2. My experimental results.  Putting the transducer to the bone behind my ear and exciting it with a sine wave, I could hear a tone up to around 50 kHz.  I did have to keep increasing the drive level.  I won't be repeating that experiment; above 50 kHz or so, all I got was a headache.  As for my four cats; the young ones (3 and 4) sat by the door staring curiously, the middle aged one (12) meowed, and the older one (15) slept (I think she's deaf).

3. All this got me to thinking, so I did a literature search.  A report from the Journal of the Acoustical Society of America (Corso J. Bone-conduction thresholds for sonic and ultrasonic frequencies. J Acoust Soc Am 35:1738-43, 1963) reports that the traditional human guinea pig (aka college students between 18 and 24 years of age) can hear out to 100 kHz under these conditions.

4. Interestingly enough, the other thing I found was reference to some research where they used an ultrasonic signal which was amplitude modulated, very much like an AM radio (eg: a 100 kHz carrier and a 2 khz voice band signal) and the test subjects heard not the 100 khz signal but the modulation.  Very interesting result.

My apologies for the digression.  I think you need not concern yourself with a small squeak.

When I learn how best to use the test gear, I'll report back if I find anything interesting about the cleaning sweep.


tron

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #36 on: November 03, 2012, 10:52:51 PM »
My cats may not like the experiment (the always sit outside the door to the workshop and meow when I play with ultrasonics), but I think I can confuse them for a few minutes for science.
Nooo poor cats. If there is not such thing as ... cat ear plugs  ;D put them in a room far away and close the door.

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #36 on: November 03, 2012, 10:52:51 PM »

HoneyBadger

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #37 on: November 04, 2012, 12:42:16 AM »
I have had two 5dIII (returned one) both made 2 high pitch noises when turning it on and off while it said it was cleaning so I would not worry about it. I am also one of those can can tell if a crt is on anywhere in the house. And those damn apple chargers for their laptops drive me crazy with their high pitch noise!
5dIII; 40mm 2.8, 16-35mm 2.8L II, 100mm Macro 2.8L IS, 70-300 4-5.6 IS, 70-200mm 2.8L II, 24-70mm 2.8L II

dlleno

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #38 on: November 06, 2012, 02:06:33 AM »
I have had two 5dIII (returned one) both made 2 high pitch noises when turning it on and off while it said it was cleaning so I would not worry about it. I am also one of those can can tell if a crt is on anywhere in the house. And those damn apple chargers for their laptops drive me crazy with their high pitch noise!

If you are hearing CRTs from NTSC Televisions, you know you can hear 15.7 KHz then :-D  Computer monitors generally run well above the threshold of human hearing. For example, a CRT capable of 1024 lines at a 60 Hz refresh rate runs at about 64KHz, which means in order for these devices  to be audible you would have to be hearing some subharmonic, which of course is quite possible. 

laptop chargers are a different animal.    Unlike the CRTs with flyback transformers, these are switching supplies running well above the audio range,   However, it is still not uncomon for these to produce some subharmonic mechanical vibration or even a real resonance in the audio range as a side-effect.  It wouldn't suprise me if these produce acoustic energy well below the upper threshhold of human hearing. 

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Re: 5D Mark III sensor cleaning noise (squeaks)
« Reply #38 on: November 06, 2012, 02:06:33 AM »