Possible lab: Audio effects in Audacity

Here's a rough idea for a lab for students to do. Not sure where it would fit in the curriculum, but it could hopefully be adjusted to fit somewhere.

1. Open Audacity. If you're using a desktop computer in a lab, it likely has it installed already. Otherwise, if it's not installed on your own computer, download it from http://audacity.sourceforge.net/download/



2. Click the red circle record button near the top of the window and record a short audio clip of yourself saying something like "testing 1 2 3" into the computer mic. If you're using a Mac the audio the default audio input should be correct and it should work, but if you're on another operating system you may need to go into Audacity's preferences and mess around with the inputs to find the right one.

3. Now you have a basic waveform to work with. Make sure it's not too quiet or too loud--if it is, adjust the input volume slider in the upper right corner and rerecord.

4. This lab will examine some of the effects that you can produce in Audacity that involve (usually) selecting parts of the waveform and running a filter on it to change its structure. A handy reference can be found here: http://audacity.sourceforge.net/manual-1.2/menu_effects.html. Go through and try applying all the internal effects to your audio clip, one by one. Make sure to select the potion of the clip you want to change, or you won't be able to apply any effects, and to undo the change after you're done so you're able to tell exactly what the next change does. Try doing each filter with different parameters and figure out how they relate to the resulting sound of the clip.

5. Once you've seen what the different filters can do, try zooming in until you can see the individual samples that make up the audio file (http://audacity.sourceforge.net/manual-1.2/toolbar.html for reference). Then use the draw tool to try editing some of the samples and see how that changes the audio. Note: Each sample is only a very tiny portion of audio. Editing only one won't produce an audible effect, so edit a lot of them if you want to actually hear what is happening.

6. Finally, one more useful thing to do is to configure Audacity to work with MP3s. It does not come with the ability to do so, but you can easily install MP3 compatibility. Follow the instructions here: http://manual.audacityteam.org/help/manual/man/faq_installation_and_plug_ins.html#lame

7. Try doing some more things in Audacity. A small library of sounds can be found at [link to Janet's sound library goes here when it's uploaded onto the Smith servers]. Try joining and mixing different audio clips, exporting and importing MP3s, and whatever else you can think of. If you're feeling adventurous, try downloading extra filter libraries (there are links on the Audacity site, or use Google) and installing them.

What's the value of all this? It can help cement a beginner's understanding of sound waves (the ability to zoom out and see the large peaks and valleys of the wave as well as zoom all the way in down to the sample level), as well as provide practice using some simple, but very useful, tools for audio editing. Knowledge of these tools could be very useful in the future if you need to work with a sound file that needs simple editing, as Audacity is great for this purpose.