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Thread: Bat detector

  1. #526
    Senior Member
    Join Date
    Jul 2014
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    2,330
    Quote Originally Posted by aethertech View Post
    What is your ultrasound application?

    at
    Passive Acoustic Monitoring (PAM) on underwater glider (6-channel volumetric array)

  2. #527
    Quote Originally Posted by WMXZ View Post
    Passive Acoustic Monitoring (PAM) on underwater glider (6-channel volumetric array)
    I am imagining a boat, open water, sunshine and sun block. Must be fun...

    Can I assume you are monitoring biological sources? Do you do any spatial processing as well?

    What sort of hydrophone are you using?

    Awesome...

    at

  3. #528
    Member
    Join Date
    Nov 2018
    Location
    Netherlands
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    83
    Maybe people think we might still be struggling to get the device working properly. This is not the case, we are just looking to get it to work even better than it already does.

    The next path was investigating how much we could gain by not using mic-in but using line-in instead, so I did some experiments.


    I tied some tests with a tone ladder injecting signals on mic in and line in at 0, 10 and 20db
    I did not really see any difference, just one important difference was noticed. When ik signal generator was disconnected the noise level dropped after a few miliseconds. Looking like some "mute" function on the line input.

    After these tests I wanted to confirm what I found on a bat recording so I set op my dac and speaker and recorded using the SPU microphone and amplifier in the style I was used to. Amplification was set to 9db for both line-in and mic-in.

    This is an image of two recordings, the upper is on the line in, the lower is mic in.

    Click image for larger version. 

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    You can see lighter vertical lines at the moments where no sounds are registered, they are similar to the lower noise signal i did see after disconnecting the signal generator in earlier tests.

    I took some spectrum images at different points. This one is the spectrum around the ping at about 0.07-0.08

    Line in
    Click image for larger version. 

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    Mic-in
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    This piece is the silence between two "pings"at 0.08 - 0.18

    Line-in
    Click image for larger version. 

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    Mic-in
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    These are the short pings (feeding sounds) at 0.33-0.36

    Line-in
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    Mic-in
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    Somehow the silences seem to be more silent but at the pionts where we are registering some sounds we can see almost no difference in the signals and the noise.

    To me it seems the mic in will get us recordings just as good as the line input.

    Edwin

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