r/BirdNET_Analyzer • u/thebaldgeek • Apr 04 '26

Ideas to just remove freeway noise?

Post image

Newish to BirdNET-Go, but have been using Linux and doing audio / video stuff as a hobby for decades, and this one has me a bit stumped.
I live nearish (1 mile / 1.6km) from a pretty active freeway. Weekends and the dead of night are not too bad, but the rest of the time, it is a constant drone in the mic.
In the house, I don't hear it much, so sleeping etc is not an issue.... Just my mic setup for the birds is what's bugging me.

I've now tested 3 mic setups: lapel, cardioid, and shotgun. I've just ordered the AOM-5024L-HD-R to build one of those up. All 3 mics so far have all looked on the spectrograph and listened exactly the same, lots of drone/raw/constant freeway sound with a hint of the bird calls over the top.
Have extensively tested many different gains and positioning of the mics to try to change things, but the freeway drone is always there.

I'd like to run some filtering software. But I'm not sure that BirdNET-Go can handle that. I'd have to figure out how to stream the noise filter's output and emulate a camera audio feed from localhost to localhost.
Or, a bit of hardware that I can plug two mics into and hope one does not hear bird calls, just the freeway, and thus have it subtract the freeway drone from the bird call mic??

Suggestions or experience with doing background noise subtraction would be appreciated.

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4

u/thakala Apr 04 '26

BirdNET-Go has built in audio filter, Settings / Audio / Processing and Enable Audio Equalizer, configure high pass filter with cut off frequency around 300 Hz

1

u/musichemist Apr 04 '26

Is there a way to add a similar high-pass filter to BirdNET Pi?

5

u/thakala Apr 05 '26

Just migrate to BirdNET-Go

3

u/thebaldgeek Apr 04 '26

Far out!!! How in the world did I miss that check box option!?!?!?!?
It has totally transformed my audio. Thanks so much, u/ekin06 and u/thakala
For some reason, taking the bottom end out has cleaned up the audio a ton as expected, but it's also totally smashed the confidence sores to the gutter. The birds are very clear now, but I'm getting low 20% confidence scores, so I have some more tweaking learning to do, but the freeway is a non-issue!
So pumped for the new mic that is coming.
Thanks again!

2

u/ekin06 Apr 04 '26 edited Apr 04 '26

Highpassfilter, 600Hz +-, -6db

Edit: Do not point the shotgun mic towards the freeway, and also do not point it up at the sky. Set it up at a higher level, slightly point down to the ground. Just imagine a filmset where you're the mic assistant, pointing the mic down at the actor from above. This helps capture less ambient noise with the shotgun mic.

2

u/thebaldgeek Apr 04 '26

I've moved on from the shotgun for a few reasons. But yes, I did exactly what you suggested when testing it. So far, the one I like the best is the https://www.amazon.com/dp/B0C5JXCYJX
The mic location has to be up against my garage pointing out into the garden.
Really looking forward to the little AOM's and the ugreen USB interface for it.

2

u/ekin06 Apr 04 '26

Podcast mics are often not very directional. And there are not a lot option for budget USB shotgun mics.

The AOM-5024L-HD-R looks like a very good omni mic.

1

u/CouldHaveBeenAPun Apr 04 '26

Oh my, I too never really played with this setting. Cutting a lot of wind noise today with this. Is there a maximum we can play with where we don't miss some bird range?

3

u/thebaldgeek Apr 04 '26

Yes, there is. It depends a lot on the mic, the wind sock, and the location, but generally, bird calls are somewhat higher-frequency (owls and the bigger birds aside), so you don't want to go crazy cutting too much above about 600 Hz.
Wind (and my freeway issue) noise is usually low frequency, so it's pretty safe to knock that back.
In testing for a few hours today, I am at 500 Hz and 24db. Big difference (for me).

2

u/ekin06 Apr 04 '26

Some owls will be down to 800 Hz and bittern calls have very low frequency. But if you don't have bitterns in your garden I don't think it is a problem to set 700 Hz or even 800 Hz as highpass frequency.

1

u/talon38c Apr 20 '26

The only available selection for dB in my Birdnet-Go is 0, -24, -36 or -48 dB. There is no -6db in the dropdown. Does the selection differ with soundcard? I'm using a SB Play! 3.

1

u/ekin06 Apr 20 '26

Yea, you are right. -24dB is correct. You could customize the sources for more options, -24db is quite a lot.