iMac: Microphone Only Records At 44.100 kHz Sampling Rate

The iMac computer supports 16-bit CD-quality stereo input/out; additionally, the iMac computer has a fixed sampling rate of 44.100 kHz. Since the sampling rate is fixed at 44.100 kHz, sampling at 22.050 kHz is not possible on iMac computers.

How to resample sounds to 22.050 kHz

The iMac computers ship from Apple with QuickTime 4 basic edition. One of the most useful applications included with QuickTime 4 is QuickTime Player. With QuickTime 4 basic, QuickTime Player is simply a media player. With the QuickTime Pro Player, users can import/export any sound document into and out of QuickTime Player. For information on updating QuickTime 4 to the Pro version, check out Apple's QuickTime web site on the internet at:

<http://www.apple.com/QuickTime/>

QuickTime Player can easily downsample SimpleSound documents to lower sample rates. To downsample a SimpleSound document to a lower sample rate, QuickTime Pro users can do the following:

1. After saving the sound document using SimpleSound, open the document using QuickTime Player.
2. Confirm the sound document's Sample Rate by choosing "Get Info" from the Movie menu and select Sound Track from the left pop-up menu and Format from the right pop-up menu. You should see 44.1 kHz.
3. Close the sound document's Get Info window.
4. Choose Export... from the File menu.
5. Select which type of file you want to export (Movie, AIFF, System 7 sound, Wave or ulaw).
6. Click the Options... button.
7. Click the Settings... button in the sound section of the dialog box.
8. Pick the new sampling rate you want by picking the pop-up menu next to kHz.
9. Click OK twice.
10. Click the save button.
You will have your sound at the new sampling rate.

Why Resample?

Sounds stored in 44.100 kHz can take up large amounts of file space. For example, one minute of music audio can be 10 MB in size using 44.100 kHz, whereas by resampling the same audio to 22.050 kHz the file will be 5 MB in size. Further reduction to the file can be made using various compression formats. However, as a general rule, as audio files are compressed and resampled, they lose quality. Depending on type of audio file this may be acceptable.