Remove frequency ranges

I have some tracks here where only a certain frequency range is of interest. How do i remove all other frequencies from the track so that only the range i want remain? Let’s say that the range is 410-430hz.

Let’s say that the range is 410-430hz.

That’s the range you want to keep, right? What you’re looking for is called a band-pass filter.

The opposite (to remove a range of frequencies) is a band-stop or band reject. The two other standard filters are high-pass and low-pass. A very-narrow band-stop filter is called a “notch filter”.

I don’t believe Audacity has a built-in band pass filter but you can make one by first low-passing at 430Hz (removing/reducing everything above 430) and then high-passing at 410Hz (removing/reducing everything below 410).

Note that filters (analog or digital) are imperfect and and some frequencies outside of the pass-band will get through and you are trying to filter a VERY narrow range. There is a slope (dB-per-octave) that defines the “sharpness” of the filter. The cutoff frequency is always defined as the -3dB point, no matter the sharpness of the filter.

There are some weird things that happen with very strict frequency filtering.

We should have no trouble filtering out everything but that frequency range and you should be very happy as long as none of the tones in that frequencies range ever changes. The minute you get a volume change or turn any tone on or off, that process generates other tones outside of the limit. If it’s a strict limit, you run into the oddball problem of not being able to turn a tone off. The system will ring like a bell and make that tone which then dies out very slowly.

What’s the job?

I’m putting money on not being able to satisfy the job no matter how we filter the tones.


Thank you all. I was looking to get a tone with a constant frequency so there isn’t a problem about the frequency changing and i getting distorted sounds.

You can create an Equalization curve like this:


Note the blue lines are the design center and the green squiggles are what’s actually going to happen.

That illustration is centered at 1000Hz. That green error effect gets worse as you go down in frequency.

looking to get a tone with a constant frequency so there isn’t a problem about the frequency changing and i getting distorted sounds.

That’s a better description of the effect, not the job.

If “getting” is the same as “generating,” is there anything wrong with Generate > Tone? Those are precise and don’t change over time unless the computer plays them badly. If it does, that’s a computer problem.

If the job is to have a tone playing in addition to a performance, you can generate a pure tone on its own timeline and both will play at the same time and export to a mixed sound file unless you stop them.

That’s real-world sound and a tone at 420Hz.

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Very high accuracy Spectrum Analyze of just the tone.

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