Bandpass filter

Audacity Help Forum Windows
1

Hello

I am a relative novice to Audacity.

I am using Audacity 2.0.5 out of the box. I would like to use a bandpass filter (with a steep slope to make it quite “watertight”). I notice that there is a low-pass and a high-pass filter provided but cannot find any bandpass filter(s). Is it possible to get a bandpass filter in audacity? Any advice would be just great,

Thank you

Andrew

2

You can create bandpass filtering by applying both a highpass and a lowpass filter.
For example, if you wish to pass the frequency band between 400 Hz and 4000 Hz, then apply a highpass filter at 400 Hz, then a lowpass filter at 4000 Hz.

3

Hi Steve,

Thank you very much. Yes. I thought of that too but was hoping there may be a plugin or a ready-made effect that would allow multiple bandpassing e.g. 0-320Hz (ok… LP if you like), then 2,400Hz - 2,600Hz then 10KHz - 15KHz. These numbers are just illustrative - not what I am really trying to do.

I thought of using an equalizer but the filters are not steep enough and allow too much leakage.

cheers and thanks again
andrew

4

Yes you can use the Equalization effect, but use the “Draw Curve” view rather than the “graphic equalizer” sliders. http://manual.audacityteam.org/o/man/equalization.html

Here’s an example of a very deep and steep bandpass filter. Note the positions of the slider controls as well as the drawn curve:
bandpass.png

5

Thank you very much. That is the sort of thing I was looking for.

Andrew

6

Hello.
I have another questions. I am blind and It is problem for me to draw a curve using this effect. So, how to band pass It?
Thank You.

7

If 20 dB attenuation in the stop band is sufficient, then you could use the “Graphic EQ” effect (in Audacity 2.3.3). The Graphic EQ should be accessible for VI users.

If you require more attenuation than that, then you could use the high pass and low pass filters (lower down in the Effect menu).

8

OK, but can I use instead classical filters too, or not?

9

If it is accessible, then yes you could use Classic Filter (I’ve not used it in a long time, and I don’t know how accessible it is)

10

Yes it’s still shipped as part of Audacity but it is not enabled by default - you can use the Plug-in Manager to enable it/

See: https://manual.audacityteam.org/man/manage_effects_generators_and_analyzers.html

and: https://manual.audacityteam.org/man/classic_filters.html

WC

11

People, I have another question for this topic. Band pass filter uses pass band ripple, or is It something different?

12

The [u]User Manual[/u] has some information about the filter options. The Butterworth filter is “maximally flat” (no ripple).