High Pass filter on multiple files equalizes their length

[jetsound]

Hi forum folks

New on Audacity and audio editing in general so bear with me if my questions have been answered previously

I have a bunch of variable length .wav files which contain speech and what I'm trying to achieve is remove unwanted lower frequencies which make the sound too "boomy" when played at a higher volume, especially with a sound system including a subwoofer. A simple high pass filter above approximately 100Hz will do fine.

Problem: I can do this easily to a single file, or all files individually. But, if I import all files (tens) as individual tracks and apply the filter to them simultaneously (which saves time and effort obviously), Audacity adds silence to the end of the files, making them equal to the length of the longest file (track) in the project. How can I get rid of this effect? I want the files to remain in their original length after filtering them.

Thanks for any replys

[steve]

The issue is caused because Audacity has to process the full length of the longest track, and because all the tracks are being processed in parallel (which is very quick and efficient) it means that every track is processed for that length of time, thus creating silence to pad out shorter tracks to the same length.

One way round this would be to select the tracks one at a time and use Ctrl+R to repeat the last used effect.

The other way is to set up a "Chain" (from the file menu) and process a bunch of files as a batch (apply chain to files). This method would allow you to process lots of files in sequence without user interaction, but take care with how many you select - Audacity will create temporary files for each track that is processed and these temporary files do not get cleared out until you close Audacity, so disk space usage just goes up and up with each file processed.

[jetsound]

Thanks. That brings another problem along then. I've understood that the high pass filter effect can't be used with chains. Is this true?

[steve]

You can't use the high-pass plug-in filter, but you can use the Equalizer to perform a high pass effect

[jetsound]

You can't use the high-pass plug-in filter, but you can use the Equalizer to perform a high pass effect

I assume I would need to understand the Nyqvist language to write my own chain, which is something I don't know how to do yet. To get me started, how would one set up a chain for example to include an equalizer to roll off everything below 100Hz at 24db / octave ? This is what I would need to do with the high pass filter.

[steve]

I assume I would need to understand the Nyqvist language to write my own chain

No not at all, it is quite simple really.
The hardest bit is setting the Equalizer.

It is probably easiest to make your Equalizer settings first.
Here's a screenshot that may help (click on it to view full size)

Screenshot.png (16.89 KiB) Viewed 1254 times

Notice that I have saved the setting with an appropriate name.

Once you have made your settings to the Equalizer, to create the chain:

• "File > Edit chains"
• Click on "Add" button and enter an appropriate name, then click OK. With your new chain selected, you will see in the right hand window that the only command listed is "End"
• To add the Equalizer as an additional command, click the "Insert" button, and select Equalizer by double clicking on "Equalization" in the list of available commands. You need to select your high pass pre-set, so before clicking the OK button click on "Edit parameters". The last preset used should be selected automatically, but if it's not the one you want, then select the preset now, or, simply adjust the Equalizer to how you want it.
• Click OK in the Equalizer window, then OK in the "Select Command" window. Your Equalizer is now included in the chain.
• You also need to have "Export" in the chain (after the Equalization command, but before the End command, so add this in the same way.
• You can add other commands, if you wish, in just the same way - make sure that Export (either as WAV or as MP3) is the final command before "End".
• When you have finished creating your chain, click OK in the Edit Chain window.

You can now select your chain and apply it to a bunch of files by selecting "Apply Chain" from the File menu.

Try it out on one short file first to make sure it works correctly (make sure you have a backup copy of the original file in case you've got anything wrong).

When you apply the chain to a bunch of files, don't do too many at once or you will run out of hard disk space. Audacity keeps all it's temporary data untill you exit Audacity.