After you’ve used Mac OS X for a while, its built-in alert sounds can get downright grating, as can many of the sounds you hear in Mail, iCal, and iChat. Happily, creating a custom alert sound and adding it to your system isn’t too complicated.

Most alert sounds should be short, subtle, and easy to tolerate even if they repeat multiple times within a few seconds. Here are some easy ways to capture new sounds.

Record new sounds

The easiest way to find a new sound is to create it yourself.

QuickTime Player  Open QuickTime Player and choose File > New Audio Recording. On the right side of the Audio Recording Window a small arrow button points down. Clicking this arrow reveals a pop-up menu that lets you choose a microphone (either the one built into your Mac or a high-quality external mic), the quality (choose Maximum), and a default location for saving the file (choose the desktop). Click the Record button, create your sound, and then click Stop. Now click Play to review the sound.

Fine-tune your sound by choosing Edit > Trim, and you’ll see a small waveform representing the audio. Drag the yellow bars at each end so that they encompass only the alert’s waveform. Click Play to preview the new, shortened sound; if you’re happy, click Trim. Now choose File > Save As. Name the audio file and save it to your desktop.

Voice Memos app (iPhone or iPod touch)  Once you’ve captured a sound, tap the list button in the bottom right of the screen. Choose the sound you just recorded, tap Share, and email it to yourself. Here, too, you’ll need to trim the audio clip to eliminate silence before and after the alert sound. Open the sound file with QuickTime Player, use the trim feature to resize it, and save the file to your desktop.

GarageBand ’11  GarageBand is particularly fun, because it lets you create simple alerts using musical notes from a huge range of software instruments. OS X requires that all alert sounds be AIFF (uncompressed Audio Interchange File Format) files, and OS X 10.6’s QuickTime Player can’t save audio in this format. So you’ll need to pass your audio files through another application before the operating system can use them.

Convert your sound

When it comes to converting the sound you recorded, you have a couple of choices.

Use iTunes  Drag the clips into iTunes to add them to your Library. Now choose iTunes > Preferences. Under General, you’ll see a section for ‘When you insert a CD’. Next to it is a button called Import Settings; click that to change the app’s audio conversion method. Choose AIFF Encoder from the first pop-up menu and click OK; click OK again to return to your library.

Find the newly added audio clips, and Shift-click each one to select them all. Now choose Advanced > Create AIFF Version. The AIFF duplicates of the files will appear in seconds. Drag these files to the desktop, and you’ll see they have an .aif extension.

Use GarageBand  Open GarageBand and, if necessary, choose File > New. Double-click Voice (under New Project), give the ‘song’ a name, and click Create. Now drag the sound clip into the GarageBand workspace, making sure the coloured block representing the audio sits as far to the left as possible. Choose Share > Export Song To Disk, deselect the Compress option, and click Export. Again, name and save the file – save it to the desktop. That file will be an AIFF file.

Add sounds to your system

Popping the new sounds into the OS is easy. In the Finder, choose Go > Home. Double-click your Library folder, and then find and open the Sounds folder. Drag and drop the audio files into this folder to make them available to all applications that use alert sounds.

If you want the sounds to be available to your family members’ user accounts Option-drag the audio files into the shared user folder at Macintosh HD/Users/Shared. Your family members can then collect the custom alert sounds from this folder and drop them into their own Sounds folder at userfolder/Library/Sounds.

Adding custom alerts allows you to personalise your system in an entirely new way, providing a much richer (and potentially more intuitive) experience with your Mac.