I have problem finding the 'true' speed of sound in aluminium, all I found ranging from 5100 to 6300 m/s. Which number (which velocity) did you use to calculate 1/2 lambda for your horn?
Yeah, the numbers vary over quite a wide range, probably depending slightly on which particular alloy it is. I used a low figure (say your 5100m/s), which will give an overestimate of the length, so you can then gradually machine it down to tune it. To be honest, I was extremely generous, and had to remove quite a lot of material!
I am interested in transfer of ultrasound from transducer to air. Is there better way than just bare transducer and short horn from ultrasonic cleaners? I have one at 40 kHz, and found that perforated PCB (FR4) gives 3 times better coupling than bare surface. I have no tools to make more holes, or different shape... is out there some article on that? Thanks.
Hi - I'm afraid I don't really know much about air-coupled ultrasound - I have seen people using a conical tapered horn with a very large end to levitate particles. The trick seems to be to try and increase the amplitude quite a bit, since air is a low-impedance medium, whereas metal (the horn) is high-impedance. Try searching around for "acoustic impedance matching ultrasound" and see if that throws anything up.
Thanks. I found rather interesting "acoustic lens" and together with "ultrasound", it gives me exactly what I accidentaly found - some sort of fresnel zone plate, or way to better focus and impedance match ultrasound, but mostly (pseudo) flat surface. I did just place PCB with many 1 mm holes in it, and it works to some extent. Now I see that fabricating better plate will be challenge, especialy to me because haven't proper tools for processing aluminium and other materials.
Hi - if you're still interested in power ultrasound stuff, I've done a video showing the measurement and tuning process for ultrasonic horns, it might be of interest. Link here - ruclips.net/video/-E7zlQEk5MA/видео.html, Best regards, Lindsay.
![World's most efficient overunity ultrasonic water heater from WITTS[www.witts.ws]](/img/1.gif)
Awesome effect!
I'm keen on this unit. How can I reach you
I have problem finding the 'true' speed of sound in aluminium, all I found ranging from 5100 to 6300 m/s. Which number (which velocity) did you use to calculate 1/2 lambda for your horn?
Yeah, the numbers vary over quite a wide range, probably depending slightly on which particular alloy it is. I used a low figure (say your 5100m/s), which will give an overestimate of the length, so you can then gradually machine it down to tune it. To be honest, I was extremely generous, and had to remove quite a lot of material!
I am interested in transfer of ultrasound from transducer to air. Is there better way than just bare transducer and short horn from ultrasonic cleaners? I have one at 40 kHz, and found that perforated PCB (FR4) gives 3 times better coupling than bare surface. I have no tools to make more holes, or different shape... is out there some article on that? Thanks.
Hi - I'm afraid I don't really know much about air-coupled ultrasound - I have seen people using a conical tapered horn with a very large end to levitate particles. The trick seems to be to try and increase the amplitude quite a bit, since air is a low-impedance medium, whereas metal (the horn) is high-impedance. Try searching around for "acoustic impedance matching ultrasound" and see if that throws anything up.
Thanks. I found rather interesting "acoustic lens" and together with "ultrasound", it gives me exactly what I accidentaly found - some sort of fresnel zone plate, or way to better focus and impedance match ultrasound, but mostly (pseudo) flat surface. I did just place PCB with many 1 mm holes in it, and it works to some extent. Now I see that fabricating better plate will be challenge, especialy to me because haven't proper tools for processing aluminium and other materials.
Hi - if you're still interested in power ultrasound stuff, I've done a video showing the measurement and tuning process for ultrasonic horns, it might be of interest. Link here - ruclips.net/video/-E7zlQEk5MA/видео.html, Best regards, Lindsay.
Is this sine wave or square wave?
Squarewave drive to the transducer, but the actual oscillation is always sinewave.