Noise reduction is what you’re looking for. So to get rid of a specific noise, you should just record that continuous background noise by itself and then save it as a wavelength. Highlight that entire wavelength, then go to “effects”, then “noise reduction” and select “learn noise”.

Then highlight the separate wavelength (the one you want to remove the background noise from), select “effects”, then “noise reduction” and click on “reduce noise”. Now you should be able to adjust the 3 different levels of noise reduction: reduce, sensitivity and the 3rd one (can’t remember the name off the top of my head). Just keep in mind, this works well for continuous background noise like static or something that doesn’t change pitch often. If you have random noises in the background that are constantly changing pitch, it‘ll be more work for you.

Also, I agree with u/paulywauly99 . It will probably save you a lot of time and effort to control the background noise pre-production, rather than post-production.

There’s all sorts of ways to reduce noise with Audacity with Noise Reduction but it has its limits before it affects the quality of the sounds you want to keep. I’d first explore how to improve the ambiance of the room. Don’t record in the kitchen where hard surfaces abound. Put a rug or piece of carpet on your desk. You can also get mic surrounds which soften the sounds.

If Audacity's (very old) native noise-reduction is not enough, there's a free AI plugin called OpenVino that works in Audacity. it's designed to isolate speech ... https://youtu.be/eTE-8nP07tk?&t=276

It's been referenced already but step one is to try and work out what the noise is and minimise it.

I have low level background noise and apply a noisegate. At the beginning of your recording don't say anything, just have a few seconds of nothing. After recording select that portion of the audio and look at the db levels (i.e. what's the noise level). You can use that to create your noisegate which will hopefully remove it.

This video explains it and this guy has helped me a few times with his videos

https://youtu.be/Nnk7qp2TI3I?si=XtI-hVpt5rmG3KuS

Could be accidentally recording from the computer's built-in microphone ? ... https://youtu.be/iyQ4nJgGHZk?&t=100

Thank you everyone for your advices so far. Seems like in general I have a lot to learn since I have no knowledge about sound engineering at all yet. Still also find this very interesting.

Your first step should be to eliminate the source of the noise. If it's your AC unit, turn it off. If it's traffic outside, put a mattress between the mic and the wall.

Second, try using a more directional mic.

After that, any remaining unwanted sound should be easily removed with the noise reduction tool. But that's not a default setting. It's an effect you have to apply after recording.

I've recently started using audacity with a Sennheiser profile USB mic and a pretty quiet room to record audio narrations up to an hour long per session. My workflow is :

1. Noise reduction (not too much, sample a few seconds of "silent" recording first and then apply only once)

2. EQ. This one takes a bit of trial and error as every persons voice is different so you might have to just see what sounds best.

3. Normalise (I just use the default level of -1db)

4. I then apply noise gate and then listen through and remove any clicks or pops. This takes the longest amount of time.

5. Final step before exporting, I do Loudness Normalisation to -16db to -19db depending on thr recording itself.

Its quite a few steps but thats what I find yields me the best results.

But also if anybody else has any feedback or tips on my workflow that would be great.

Try running a real time EQ plugin. Use a super narrow bandwidth with the level boosted fairly high. Start at one end of the frequency spectrum and slowly sweep the bandwidth to the opposite end of the spectrum. Listen for areas where the offensive sounds/background noise seems to get louder. Once you find the worst area, turn the boost way down. This isn't a great method to rely on, but in certain situations it can be helpful.

I don't know if this will help with your specific problem and I'm sure I'm not explaining it properly, but if you want to look into it try searching YouTube for videos on "EQ sweeping" or "Seek and Destroy EQ technique".

The main thing you have to do is find and remove the sources of noise.

Treat the room, even if you have to use couch cushions, mattresses and moving blankets. Or move your mic into a more sound isolated space, like a closet full of clothes in the center of the house.

This is assuming your mic and interface are of good enough quality that they're not introducing noise. If that's not the case, replace them with something better.

Once you do those two things you'll be able to use much less aggressive noise reduction settings and it won't alter the sound of your voice nearly as much.

Noise reduction is a destructive process. So less is more.

The best place to invest time and money is to learn how to fix your audio before you even hit the record button.

That means identifying sources of noise and figuring out what you can do to reduce or eliminate them. Another thing that beginners miss is how to treat your recording space with “broadband” sound absorption. I like to say that I’d rather use $100 mic in a properly treated room than a $5000 mic in a closet.

If your recording is good, then you don’t have to do much post production at all.

That being said, Izotope RX has a bunch of great audio restoration tools for cleaning up your audio.

Supertone Clear is a nice plugin for eliminating general background noise.

Accentize has a bunch of noise and reverb removal plugins for professionals. They are used in TV and Film a lot.

With any kind of noise reduction I would do a little at a time. If I wanted to reduce noise by 12 db. I would do 3 passes of 4 db instead of one at 12 db.

Lots of good advice here. I do not like Audacity's Noise Reduction in general. If it's used lightly it can be ok, but if you need a lot of noise reduction, it really harms the sound quality.

So first reduce the noise generated by your gear (expensive). Then reduce the noise heard by your gear (inexpensive). Then use as little noise reduction as possible.

I have had much better experience with Audition's noise reduction but I've left Adobe on non technical principals and can't recomend, but it suggests there may be other better plugins out there to explore.

I find that if you’re unable to turn off any fans in your room, the AC, or still have computer sound to just let audacity record a bit of audio without you talking or making any noise so it just has the background fan noise. Afterwards you can use noise reduction, select that sound and then reduce it for the whole track. Just find the right amount to reduce it by so your quality doesn’t take a big hit and you still manage to remove enough of the bg noise. I hope this is helpful, I’m still a rookie and I’m sure there’s a better way that others will recommend.

Yes, I recommend leaving 5 seconds at least before you speak. Select that portion then go to effects and noise reduction. Select get noise profile. Now, select the entire track and under effects choose apply noise reduction.

For better effect I will normalize the audio to 0 first to get bigger peaks.

While there’s some great methods here, you should keep your eyes peeled for discounts on a plugin pack called Izotope Elements. It frequently goes on sale for ~$30 (down from like $100?) and it has an incredible Voice De-Noise effect

Its difficult. Best thing is to keep them from clapping and cheering while you are recording.

Best to turn off the fan, move the computer further from the mic, or treat your space to improve sound quality. A lot of noise removal will damage your audio and audacity has terrible noise removal.

If the projector sound is constant and there's a few seconds of it in isolation you can use the noise reduction plugin to try to remove it. That's the easiest thing to try first.

https://manual.audacityteam.org/man/noise_reduction.html

If you're planning to apply the noise removal plugin in post you should disable the automated noise gate you're currently using so you'll have a section with no voice to sample. Otherwise it doesn't work. You can reapply a gate after you do the noise removal if needed.

If Sound Activated Recording is off (it should just stop recording during silences), maybe another software is applying a system-wide noise gate, as explained here.

ensure Sound activated recording is turned off or increase the db level

https://manual.audacityteam.org/man/recording_preferences.html

Re-record, and ask for the TV to be off this time!

If the objective is isolating speech try Adobe enhance, it's free, (and better than Audacity at this task).

(It can't perform miracles like you see on CSI: that's science fiction).

Be careful with these stock settings. When boosting that high in frequency with that much gain, you can introduce noise and interference into your recording. Likewise, there's not much in the human voice below 80Hz, so boosting that low actually boosts ground loops, rumble (like garage doors), and booms (like tapping on a desk).

Thanks man this is just what I needed, seeing as Audacity won't let me use Gate (because the "Add/Remove plugins" menu is broken). This should save me a lot of fiddling!