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Trying to buy an underwater Infrasonic magnetostrictive transducer

Discussion in 'General Electronics Discussion' started by William P Hilmes, Jul 14, 2018.

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  1. William P Hilmes

    William P Hilmes

    17
    0
    May 10, 2018
    I have been trying unsuccessfully to buy an underwater Infrasonic magnetostrictive transducer projector that operates in 5 to 30 Hz range. Every time I mention my low frequency range I am told this product is not available. Does anyone know where I can buy this type product? If I am unable to buy this product is anyone willing to build this product for me or help me build it for a fee? In an attempt to build one myself I have tried in vain to buy a magnetostrictive rod for this project. All the places that I reviewed for this purchase are in China and I must buy at least 50 Kg of material not just one rod. Does anyone know where I can buy just one rod? Any help with this project would be appreciated. Thank you.
     
  2. Externet

    Externet

    754
    164
    Aug 24, 2009
    Seen your quest in other forums... Do not get the "projector" portion of your wishes. Audio will travel mostly omnidirectionally underwater.
    And seems you are blindly pursuing the magnetrostrictive thingy...

    Remove/cut-off the outer rim that attaches the cone to a speaker frame; place the speaker in a plastic bag (I use an intravenous bag, perhaps a thick resealable freezer bag will work) fill with 'baby oil' and seal it with the wire brought outside.
    Place the bag underwater and apply your 5Hz to 30 Hz.

    Any electromagnet pulling a lid from a tin can of beans can also perform. Place a piece of sponge between the electromagnet core and the tin disc as 'spring'. Feed your 5 to 30Hz when placed in an oil filled bag.
    In other words, make a speaker with a tin circle instead of paper cone.
     
    Last edited: Jul 14, 2018
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  3. William P Hilmes

    William P Hilmes

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    May 10, 2018
    Thank you for the information. I will get it a try. As you can tell I do not have much experience with electronics. I am trying to study the effect infrasonic sound on submersed aquatic plants in Lake Seminole in South Georgia. I have a two channel signal generator to send the sine wave at a specific frequency, and amplitude.

    Why do you cut-off the outer rim of the speaker frame? What type of speaker should I use? Do I need to use a sub-woofer speaker since I will be broadcasting in the low frequency range? Does the speaker need to be in resonance with the frequency that I am sending?
    I do not fully understand the arrangement with the electromagnet with the can lid. Can you draw a picture and scan the image of both the can and speaker in a bag and email it to me at [email protected]? I would be happy to pay you for any time you spend helping me. Thank you very much!
     
  4. Externet

    Externet

    754
    164
    Aug 24, 2009
    Hundreds of ways to do it...

    [​IMG]

    A larger speaker would be convenient. You need the 'basket', only.
    Secure in its center an electromagnet like :

    ----> https://duckduckgo.com/?q=holding+electromagnet&t=canonical&ia=images
    ----> https://www.ebay.com/sch/i.html?_from=R40&_nkw=holding+electromagnet&_sacat=0

    Get a gallon paint can lid and attach with silicone to the 'basket' rim of same diametre instead of the paper cone.
    Position them so the distance from the electromagnet pole 'inside' and the lid is about 4mm (guessing)

    Apply 12VAC at 60 Hz to the electromagnet from a power adapter/transformer secondary; the tin lid should vibrate at 60 Hz.
    Adjust the gap between the electromagnet core and the lid for best vibration. Try your desired frequencies instead of the transformer (audio generator + audio amplifier)

    The electromagnet will attract and repel the tin lid at the frequency applied. Does not need to be resonant.

    A normal speaker has a moving coil. This contraption would have a 'moving' magnetic field acting on a tin disc diaphragm. No need to enclose in an oil bag, but can rust at some point.

    - Start with a tin lid and look for a canibalizable speaker of matching diametre, or reverse. Then measure the room available inside for the electromagnet height and get one.

    Already made, look for 'Diluvio' ----> http://tactilesound.com/
    Or, ----> https://duckduckgo.com/?q=subwoofer...r&t=canonical&iar=images&iax=images&ia=images
    Or, ----> https://www.electrovoice.com/binary/UW30 EDS.pdf

    You can fasten this one to the bottom inside a dinghy----> https://reactual.com/audio-equipment/tactile-sound/tactile-transducers.html
    The whole dinghy hull will be your subwoofer transmitting infrasound to underwater.
     
    Last edited: Jul 14, 2018
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  5. William P Hilmes

    William P Hilmes

    17
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    May 10, 2018
    Thank you. You opened my mind to a lot of possibilities. It sound like I need to start experimenting and see what work and what fails. I will stay in touch to give you progress up dates.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I'd love to read the ethics section of your research project!
     
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  7. William P Hilmes

    William P Hilmes

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    May 10, 2018
    This is personal research for me and to satisfy my personal curiosity. This is not for a class, a company or a research journal. If I buy or make my research equipment has no bearing on anything.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Other than anything living in that body of water.
     
  9. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    I dreamed last night and came up with a solution.:)
    Take a plastic pipe and fit a speaker to one end, a speaker designed for horn loading will be best.
    Immerse the other end of the pipe in the water and adjust the depth to resonate at the frequency you are interested in. At resonance the pressure could be quite high so a stiff cone would be advantageous.

    I leave you to calculate the resonance of the mass of the water column with the air volume.
     
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