ultrasonic effects on microphones

EDIT:
here is a link to a YouTube video with sound, please ensure you have your volume control set to an appropriate level and that you use hearing protection at all times.
http://www.youtube.com/watch?v=3eso8ZjbTL8

just posting a link i'm not going to even bother
if you suggest that it's something that might

but never hurts to have protection

I saw the video with the sound off. then started to add a little volume... It's heavy machinery. Whenever working with anything in terms of machinery always wear ear protection and in most cases eye protection as well. Forget how loud it can be and such. always wear ear protection and eye protection.

right , there's a point where the impact from a high level
transient [ like a hammer on pipe ] will be equaled
by a lower level sound over a longer duration
[ lawnmovers for 8 hrs ] and gray area in between

apologies okgb,
I thought it would speak for itself.
of course, I wouldn't challenge the use of ear protection in any environment likely to be of even minimal risk. to be honest I was interested in what people might have to say about the video without my thoughts about it first, merely prompting idle conversation... I may have wrongly assumed the correct place for this type of thread tho... brewery?
maybe i could embed the video so you don't have to click on anything. i'll look into it, still not that tech savvy

anyway, it is an ultrasonic welder,
my initial thoughts were about the intense effect it had on the camcorders internal microphone. to me it is reminiscent of a bit reduced signal, or something Aphex Twin might use.. horrible digitized clipping sound.
then you see the guy doing it is blissfully unaware of any sound, and is not concerned with protection.
hey, its not my video. he can wear whatever he wants. I would have thought audio orientated folk would be more inclined to discuss the microphones reaction/response and relevant lpf's/cause and effect etc. as opposed to the current heath and safety regulations ignored by a random factory worker.

i'll be sure to find something more interesting next time

if you ask me, you should have called the thread "do you think the audio will damage the mic" or something else along those lines and then explained to use low volume when viewing... to my knowledge you can't post videos into threads. All you can do is post the link.


darwin award? no. but definitely nothing I would way to do with out ear protection...

this seems as good a place as any
another slightly related point to consider is
I used to leave mics set up ready to go on a drum kit
at my place but realized there was no reason for the mics
to be exposed to the level when we were merely jamming
[ i got worried about my beyer 88 sitting in the kick ]

I guess mic diaphrams don't often " go " from level alone
there's usuallyage in the consideration , but not many can afford
new mics so it is prudent to think about the conditions

good points.
never really thought much about mics that were unused but still in the room except a ribbon thats covered.
i hit record just in case any magic happened at a jam once but only the 2nd tomtom mic was enabled that made for an interesting listen back

I wonder about situations like with your beyer 88,
if the mic is not plugged in at all... what determines the natural air pressure resistance without a connected load?
is this more dangerous for the mic than leaving it plugged in and just not using it?



ok ill be careful to direct conversation more with the title in future i suppose it would be interesting to know why ultra sonic sounds have such an effect on the audio produced from this mic, i thought the frequency response on these was rounded off by design or physical construction.

so, sorry about the title. lets get the safety out of the way, Please ensure your speakers are set appropriately for a Youtube(dot)com video and that you always wear ear protection if you watch this video. but that considered...

I could speculate that the sample rate used  interprets elements of these high frequency sounds differently and the result IS actually close to bit/sample rate reduction?
or that the frequencies in question have 'sub-harmonics'? which the mic picks up but are somehow inaudible to humans until played back?
either way i thought a low pass filter or the size of the mic would normally prevent these sounds getting to the media?

As long as you cannot hear it (not even subharmonics) ultrasound doesn't damage hearing.

living sounds said:

As long as you cannot hear it (not even subharmonics) ultrasound doesn't damage hearing.

Click to expand...

I disagree... but then again I am not an ear doctor so what would I know.

well, ear doctors may tell you the upper limit of human hearing is 20kHz, and there is talk about frequency above this still having an effect on humans (how we sense it etc.) as you well know. but no effect beyond this as far as i'm aware, can actually be measured sonically.

ultrasonic is anything above this audible threshold hence the name,
if i could step away from the hearing damage thing, we've all read the pamphlets, my fault for misleading title
just to clarify for those who cannot follow links/see youtube, in the video there is sound when the machine operates... however the uploader states that the actual sound is very quiet, even right next to the machine(ultrasonic).

any thoughts/theories as to how the mic did it?

One of my projects involves very high intensity ultrasonic sound, at about 100 kPa. (1 Pa=94 dB spl). I also design microphones to
pick up this sound.

It's dangerous as hell. If focused it will burn things if there is an acoustic impedance match from a resonance. Even with ear protection
it will go right through the tissue of one's head, reach the inner ear, and cause loud subharmonics due to nonlinear effects and bandwidth. I have to wear a face shield when working with it. The face shield has to be designed as a resonant device to insure the sound is blocked.

Normally there is a many thousands of times acoustic impedance mismatch between air and tissue, but not at certain resonances.

The microphones I design to pick it up sometimes shatter, even though the diaphragms are hardened maraging steel.

Ordinary audio microphones will pick up ultrasound at certain frequencies where fortuitous resonances occur. That's what's happening here,
with obvious digital aliasing.

The welder in the video uses a ceramic Langevin transducer coupled to an impedance matching horn. It's probably a hundred or two acoustic watts.
The ultrasound does not come through your computer speakers of course.


Les
L M Watts Technology

awesome!