Abrupt high and low pass filtering

Hi all,

First post so here goes :

I have 2 x audio files of a motorcycle passing through a noise test under wide open throttle.
The first file is a simulation with induction and combustion orders only (no mechanical noise). If looking at an FFT plot of the simulation the frequencies drop off sharply after 450Hz.
The second file is a recording of a motorcycle doing the noise test that includes the mechanical contribution from the engine with frequencies up to 20kHz.
What I’d like to do is cut off frequencies above 450Hz from the simulation, cut off frequencies below 450Hz from the bike recording and marry them into 1 x audio file that includes the simulated induction/combustion noise and actual mechanical (engine) noise from the recording.

Is this possible using Audacity?

Thanks, Jon

Very steep filters can be created using Audacity’s Equalization effect in “Draw” mode.
For very steep filters, set the “Length of filter” to maximum. Move the lower vertical slider on the right to scale the graph so that you can see down to -120 dB (see illustration).

Here is an example of a very steep low-pass filter with a corner frequency (filter cut-off frequency) of 1000 Hz:
and an example of a very steep high-pass filter with a corner frequency of 1000 Hz:

Thanks Steve, just the ticket :smiley: :smiley: