Anyone got ultrasound experience here?

I want to inject high power ultrasonic energy into a random mass with variable density and geometry by pressing a horn onto the surface (assume metal) of the mass (no glue or fasteners). I wish the energy to be distributed throughout the mass -- and there will be density changes along the way (high and low density liquids, gaseous volumes, metal connections). Tuning for resonance will not be possible.

Question: Without any additional details, where are my pitfalls -- what problems can I expect?

I know this is a broad question, and I can't give a lot of detail, but those with experience will understand what I am asking, I think.

 

I don't see a problem with that. Of course, ultrasound is used extensively in medical imaging.

Are you interested in transmission or reflection?
Ultrasound is used to measure density as well as for 2-D and 3-D imaging.

Here is an example of ultrasound used in diagnosing the health of trees.

https://www.naturallytrees.com.au/page/picus_sonic_tomograph_ultrasound.html

 

Are you interested in transmission or reflection?

I'm interested in directing the energy into and consuming it in liquid contained within the volume of the mass.

Edit: I want to cavitate the liquid. But the geometry/size of the system and the location of the liquid will be pretty much random.

 

I think one problem will be the horn, if you mean an air horn. There is a huge acoustic impedance mismatch between air and the assumed metal surface, so energy will be reflected rather than transferred through the surface. Or did you mean this kind of horn ?

 

Or did you mean this kind of horn ?

Yes.

 

Also, are there safety issues with handling, say, 60W@40kHz of ultrasound energy? If human flesh comes in contact with the horn, will it cause injury? This is a new subject for me, BTW.

 

Also, are there safety issues with handling, say, 60W@40kHz of ultrasound energy? If human flesh comes in contact with the horn, will it cause injury? This is a new subject for me, BTW.

Yes, there are significant safety issues. I've used ultrasonic probes in the lab - probably less power than you're describing - and recall there were required safety protocols. But I also seem to recall that the danger diminished hugely with distance from the probe. Inverse square law, I suppose.

I think the only way to get cavitation over a wide area and behind obstacles is to make a bath, like they use to clean jewelry. A point source horn can't cavitate around objects as far as I know.

 

Yes, there are significant safety issues. I've used ultrasonic probes in the lab - probably less power than you're describing - and recall there were required safety protocols. But I also seem to recall that the danger diminished hugely with distance from the probe. Inverse square law, I suppose.

Yup. I found this:

2.1 Contact Exposures

Contact exposure is exposure for which there is no intervening air gap between the transducer and the tissue. This may be via direct and intimate contact between the transducer and the tissue or it may be mediated by a solid or liquid. Contact exposure can in some cases provide nearly 100% energy transfer to tissue. However, an air gap can diminish the ultrasonic energy transferred by orders of magnitude. For example, if a person's finger is directly irradiated in the water bath of an ultrasonic humidifier, the energy transferred to the bone is approximately 65% of that which is radiated; but if the finger is just outside the water, one million times less ultrasonic energy is transferred to the finger.

The in vivo mammalian biological effects data for ultrasound contact exposure in the low MHz frequency range are summarized by the graph shown in Figure 1 (NCRP 83). The plots show the intensities below which no significant, independently confirmed biological effects have been observed.

Devices such as ultrasonic humidifiers operating in the low MHz frequency range can readily cause tissue injury if and only if there is a contact exposure. It is known from anecdotal reports that at full ultrasonic power, contact exposure of a finger to the ultrasonic beam from an ultrasonic humidifier will cause sharp pain within seconds, likely due to overheating of the bone.

There also exists the potential for hazardous effects below the MHz frequency range with high-power ultrasound. For example, high-power ultrasonic waves are used in ultrasonic cleaners and cell disintegrators because of their destructive and violent effects. It is certainly reasonable to assume that relatively intense cavitation activity occurs in the water (or solvent) baths of such devices (Ac 83; WHO 88). Nonetheless, documented cases of actual tissue damage are rare. In one documented study, exposure to ultrasound in ultrasonic cleaners operating at frequencies between 20 and 40 kHz was reported to have caused pain in the hands of the volunteers. However, exposure to ultrasound in an 80 kHz cleaner led to no immediate observable effects (Fi 68).

 

Also, are there safety issues with handling, say, 60W@40kHz of ultrasound energy? If human flesh comes in contact with the horn, will it cause injury? This is a new subject for me, BTW.

Sorry, not my area of expertise.
I am more into bone density measurements, EIT, imaging, and signal processing.

 

Also, are there safety issues with handling, say, 60W@40kHz of ultrasound energy? If human flesh comes in contact with the horn, will it cause injury? This is a new subject for me, BTW.

At this frequency and power I would worry about potential hearing damage as well.

 

Run down there to Cuba.....and see how they are doing it.

 

Contact the guys from Mythbusters. They would still like to produce the “brown note”.

 

I have worked with 2kW 22...44 kHz magnetostrictor and 1500 kHz 60W piezostrictor. Last is temporary safe for touching, but first is not. Actually nothing may be sensed, but it is written in instruction that metal box doors must be closed without of gaps. Both are making cavitation in the water, thus count that for target power if cavitation is needed.
First has AISI-306 actuator of about 10cm long and 8 mm thick, with pancake in the far end, with diameter of 15 mm and 4 mm thick. Second has reaction straight on the piezoceramics, which form the cup bottom of ca 36mm diam and 6mm thick. Both machines MUST be set into resonance, otherhow no cavitation.

 

Both machines MUST be set into resonance, otherhow no cavitation.

And that is the answer I was looking for. Thanks.

 

http://www.foxnews.com/world/2017/1...a-possibly-linked-to-u-s-embassy-attacks.html

 

http://www.foxnews.com/world/2017/1...a-possibly-linked-to-u-s-embassy-attacks.html

It wasn't me. I swear.

 

When they first said ultrasonic months ago......I was thinking >20k. I hear that sound on the video 24/7 for years now.
The sound on the video is pretty close to my ear's ring. But was easy to discern.

I thought they were damaged by sounds they could not hear.......and that was why they weren't sure the cause.

Surely most people can hear that video.......and the change in volume.

Does this mean one can take a high frequency but low power background tone 27/7 and drive people nuts?

Like me?