Tweet
I had trouble posting a follow up so I'm trying posting a message. See transducer from 2/9/00.
I recently discovered this group, so forgive me if this question has already been addressed. I did not see the answer in the replies to the original message.
The resin in a transducer should not have the same sound properties as water. The goal of the interface material (sound window) is to get the maximum amount of sound from the elements into the water and back from the water into the elements. This happens when the interface layer has an acoustic impedance that is equal to the geometric mean of the element (PZT = 38 MRayl) and the medium (water = 1.6 MRayl). So, the a single layer interface should have a specific acoustic impedance of about 7.8 MRayl. There will still be losses in the transmission between materials, but they will be minimized.
On top of acoustic impedance matching, the thickness of the interface material should be set up for 1/4 wavelength matching. That way, the portion of the acoustic energy that gets reflected at the interface will add in phase with the next wave and give you optimal energy transmission.
I have found one good site for different properties of materials. This site is http://www.ultrasonic.com/. They have tables giving the acoustic impedance (ZL) of PZT, water (fresh and salt), and a bunch of epoxy mixtures that they will be happy to make for you for the right price. They basically dope standard epoxies with finely ground metals or oxides (e.g. tungsten - W) to modify the acoustic impedance. Depending on the number of sound windows you want, I would expect the price to be $200-$300 per sound window.
If money is a concern, we have had success with an inexpensive plastic you can buy in sheets. Because we may use this plastic in a commercial sonar system, I don't want to give out the name just yet, but I would be happy to send you a chunk at our cost plus shipping. This material gives a good match between PZT and fresh water (we have not tried in salt water yet).
Good Luck,
Jarrod
I recently discovered this group, so forgive me if this question has already been addressed. I did not see the answer in the replies to the original message.
The resin in a transducer should not have the same sound properties as water. The goal of the interface material (sound window) is to get the maximum amount of sound from the elements into the water and back from the water into the elements. This happens when the interface layer has an acoustic impedance that is equal to the geometric mean of the element (PZT = 38 MRayl) and the medium (water = 1.6 MRayl). So, the a single layer interface should have a specific acoustic impedance of about 7.8 MRayl. There will still be losses in the transmission between materials, but they will be minimized.
On top of acoustic impedance matching, the thickness of the interface material should be set up for 1/4 wavelength matching. That way, the portion of the acoustic energy that gets reflected at the interface will add in phase with the next wave and give you optimal energy transmission.
I have found one good site for different properties of materials. This site is http://www.ultrasonic.com/. They have tables giving the acoustic impedance (ZL) of PZT, water (fresh and salt), and a bunch of epoxy mixtures that they will be happy to make for you for the right price. They basically dope standard epoxies with finely ground metals or oxides (e.g. tungsten - W) to modify the acoustic impedance. Depending on the number of sound windows you want, I would expect the price to be $200-$300 per sound window.
If money is a concern, we have had success with an inexpensive plastic you can buy in sheets. Because we may use this plastic in a commercial sonar system, I don't want to give out the name just yet, but I would be happy to send you a chunk at our cost plus shipping. This material gives a good match between PZT and fresh water (we have not tried in salt water yet).
Good Luck,
Jarrod
Comment