Audacity features an impressive amount of effects that you would not normally find on free, open-source software.
A lot of the effects are more straightforward. Fade in, fade out, cross fade, reverse, invert will happen at the click of a button. The other effects require some more settings before it is applied to the audio. You may want to play around and get a feel for what different effects do.
One of the drawbacks of editing sound in Audacity is that you cannot listen to your audio while editing. You cannot try out an effect as you are listening. Many effects give you the option to preview part of the clip with the affected changes.
Tip: You can loop your audio so that it repeats every time it reaches the end of your project by going to the menu bar Transport > Play > Loop Play. This can be particularly helpful for editing.
Equalization (EQ) lets you control the frequencies in your audio. Hz is the numerical measure for frequencies and dB is the numerical measure for loudness.
Here is a chart for understanding the range of frequencies in instruments:
The fundamental frequency is the lowest frequency and determines the pitch. Harmonics are the highest achievable frequency. kHz also means kilohertz, or 1000 x 1Hz.
You can make as many points on the graph as you want with the drawing EQ type.
With the graphic EQ type you can use the sliders for controlling the frequencies.
"Flatten" will flatten the changes you made and start new, bringing everything back to 0dB. "Invert" will flip around all the changes you made, everything you brought below the line will now be above the line and vice versa.
You can save and name the the EQ settings you made. You can also choose from some premade EQ settings.
Reverb is how a sound is reverberated in a space. It is the effect of tightly-spaced echoes. Sound waves bounce around a space and the reverberation sounds different in every space depending on the size and materials in a space. Reverb occurs naturally within any space and can be recreated digitally, which therefore creates a virtual space. Play around with the settings until you settle on something that sounds good to you.
Delay is an effect that will delay and repeat a signal. It is similar to reverb and echo, but it does not happen naturally. You can control the amount of times it repeats, the duration of the repeats, and the amount of the delay time.
Echo is simpler than delay and does happen naturally. It will delay and repeat the audio and decay at an amount of your choosing.
Earlier we talked about clipping. You never want the audio you record to be clipping because it is irreversible, unless you are recording an instrument that is meant to sound distorted. Distortion happens when the voltage needed to reproduce sound waves at their peaks is higher than the amount that an amplifier or speaker is capable of. In turn, the sound waves will be clipped off at the peaks and sound distorted. Here is a visual example:
You can play around with the different types of distortion to find what you like.
With Audacity, you can change pitch without changing the tempo. You can do this by pitch or by frequency, allowing you to transpose any audio you have to a different key.
When you change the speed, you affect both the tempo and pitch. Speeding up makes the pitch higher and the tempo faster, slowing down does the opposite.
You can also change the tempo without changing the pitch. With Audacity all these three changes are possible, which again, is not something you would normally find on a free, open-source software.