The three most common audio standards on the web come from the three most common computer standards. Audio files used on UNIX computers have the extension .au in their names. Audio files for Windows computers have the extension .wav , and those for Macintosh computers have the extension .aif . All three types of computers can play all three types of audio files. When you record audio on your computer you should remember to save it with the appropriate extension in it's name.
Audio files can be extremely large.
Also, the better the quality, the larger the file. The lowest quality audio is what you normally get over the phone, and the highest quality is audio on CD's. When you make your recordings, you should start with the lowest quality and go to a higher quality until you are satisfied with the result. Since these two types of audio files can be so large, it's not advisable that you record very long texts. Nothing longer than about a sentence or two in length.