OT: when you try to record dolphin, but result is mostly radio interference
My long-time friend Julian trying to record some underwater acoustics with resident dolphin known as Randy. Well, long chain of equipment (hydrophone, pream, macbook with some adapters because apple eliminated normal separate audio line in/outs) resulted in this: https://drive.google.com/drive/folders/1Mm_Gt8XneZI5fFAgJcy4lE6G5vNcALlI?usp... For some reason Audacity for mac refused to record above 44.1 Khz sampling rate, so all sound still limited to around 22 Khz frequencies. I suggested Ubuntu studio 24.04 but while personally testing my suggestion I run into problems, spend some time resetting win 8.1 on laptop (there was magical command to make Windows boot again but you need Windows install image for it to work ...)
More than Ubuntu Studio I recommend AV Linux from "our" Glen. And more than Audacity I recommend Ardour... (but even better: GarageBand, it is MacOS native)
The radio signals which are interfering could be shortwave. I would recommend using ferrite clamps on the cables which do not carry digital signals, especially those in the most sensitive area, like from the hydrophone and pre-amp. Also the pre-amp power cable, if it is not battery powered. And screen the pre-amp, if it is not in a metal box. The pre-amp itself ought to have provisions for preventing this, like a low-pass filter at the input. MatN
вт, 30 апр. 2024 г., 12:01 Mat via Cin <[email protected]>:
The radio signals which are interfering could be shortwave.
I would recommend using ferrite clamps on the cables which do not carry digital signals, especially those in the most sensitive area, like from the hydrophone and pre-amp. Also the pre-amp power cable, if it is not battery powered.
*I think* preamp in this case is battery-powered. By ferrite rings you mean like those? https://www.ebay.com/itm/403346040770 And screen the pre-amp, if it is not in a metal
box. The pre-amp itself ought to have provisions for preventing this, like a low-pass filter at the input.
MatN -- Cin mailing list [email protected] https://lists.cinelerra-gg.org/mailman/listinfo/cin
On Tue, 30 Apr 2024 12:16:57 +0300 Andrew Randrianasulu <[email protected]> wrote:
*I think* preamp in this case is battery-powered.
By ferrite rings you mean like those?
Yes, those ferrite clamps; an nearby electronics shop or ham might be of assistance. They are also used to prevent computer signals _causing_ RFI, e.g. on VGA cables. It is often difficult to determine where the RFI (radio frequency interference) is picked up. If the hydrophone cable is differential (two opposite signals, with a separate shield) usually via a XLR connector, then _in theory_ that cable should be less suspectable for RFI. The pre-amp still might be, if it's common mode signal rejection for high frequencies is not good. It can even be caused by badly configured XLR connectors/plugs, but I don't have those details anymore; it has something to do with grounding of microphone cable shield and signal ground. As a quick test wrap any item which processes the still analog signal into aluminium foil, to determine which item picks up the RFI. Some readings (search for "EMI/RFI XLR", or "EMI/RFI audio" if not XLR): https://service.shure.com/s/article/radio-interference-on-a-microphone-cable... MatN
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Mat