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Help identifying mysterious noise source
Old 21st July 2019
  #1
Here for the gear
 

Help identifying mysterious noise source

Got a Samson GoMic that plugs into my laptop via USB.

In two rooms of my house I get this awful noise:
https://vocaroo.com/i/s0t9giQtDawf

The noise has an intriguingly regular spectrum:
https://imgbb.com/

The noise is there even when the laptop is unplugged from mains, and even when all the electricity to my flat is switched off and also all the phone cables are disconnected.

The noise depends on the orientation of the USB cable - at different angles it picks up more or less noise.

The noise is only in two rooms of the flat (one vertically above the other) and not any other rooms.

The exact same noise is present if I try:
different laptop
different usb cable (even high quality shielded)
different USB microphone (also tried Samson Meteor)

However I do not get the noise with a FiFine wireless lapel mic that has a USB connector at the wireless receiver end. The mic connects to the transmitter via mini XLR, which should reject EM interference picked up along the mic cable.

Any ideas what the cause is? I mean from the evidence above it has to be radio interference from a neighbour or nearby source that is somehow influencing the microphone in those two rooms. I am mostly curious if anyone can identify what it is. I guess I won't be able to fix it unless I start knocking on neighbours' doors and asking them to turn off baby monitors etc.....

Any ideas received with interest....

PS I am aware that the signal passed down the USB cable is purely digital, so the interference is not having its effect on the signal there, but it seems that the USB cable is somehow picking up interference and passing it through to the circuitry of the mic...)
Old 4 weeks ago
  #2
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mekanik's Avatar
 

THAT noise my friend comes from either your computers gpu, or psu or mainboard voltage regulators. and it can spread through the ground plane of it.
It can aslo come from any device you have that has a pwm/"switching"/non linear heavy copper transformer psu. And the more "efficient" that psu gets the more you will hear this crap.

I had this noise from a brand new top of the line motherboard/psu/and graphics card. like a 200€ card. and the psu was over 100€, a seasonic silent one, seasonic is the best sh1t there is on the market (consumer market), and the motherboard was a top of the line gaming asus one.

I tracked it down to the psu and motherboard on my system. the voltage regulators on the mainboard does this too. but the main culprit was the psu. its ultra efficient and "platinum" rated. its simply pwm-ing at like high khz freqs. and this is what you hear.

I solved my problem with going all balanced cables out of my soundcard. and balanced all the way to the monitors. this reduced this noise by maybe 40db or so. but its not completely gone. I have to turn up the vol to 90% with nothing playing to clearly hear it now.

Now this is from a stationary computer. but it will just the same from everything with pwn psus and similar tech as computers. laptops are notorious for this noise. Balanced all the way solved most of it.
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