We have extensively covered an issue where some MacBook Pros generate a high-pitched, irritating whine.
As noted in our MacBook Pro special report and several follow-up reports, the problem has to do with power draw. When a certain amount of power is being drawn, the problem manifests. This explains why some users experience alleviation of the noise when toggling display brightness or turning off one processor using Apple's CHUD tools (which are included among the Developer Tools that ship with the MacBook Pro).
The most common fix has been turning on the MacBook Pro's built-in iSight, which temporarily changes the power draw.
One easy way to turn the iSight on quickly is to use the Mirror widget, simply activating Dashboard whenever the noise becomes apparent. In fact, some users have reported that turning on the iSight temporarily then turning it off results in a lasting elimination of the noise (until the next restart). [For more fixes, see this section of the special report]
However, as noted separately, the Intel-based Mac keyboard update released a few days ago eliminates the effectiveness of some workarounds for reducing the high-pitched whine.
We've now obtained a graph visually displaying the noise when read through a system capable of recording up to 55 to 60kHz noises.
The graph has been marked where computer wakes from sleep via a mouse click, when the whine starts, and when PhotoBooth is launched and quit. There is also a reference the 20000Hz frequency mark (commonly accepted auditory threshold of audibility for frequencies). No tasks were carried on the computer while this was running, except launching PhotoBooth.
As you can see, there is a significant difference when the whine is present. you will also notice brief periods where the whine is briefly interrupted -- generally due to a change in power draw.
- MacBook Pro Special Report follow-up #8: Display slightly bent, not latching properly -- solutions; cooling solutions; more
- MacBook Pro Special Report follow-up #7: Repeated system freezes or sudden restarts -- Checking for bad RAM
- MacBook Pro Special Report follow-up #6: Clock speed of ATI X1600 card; Shift key not recognized; more
- MacBook Pro Special Report follow-up #5: Apple addressing issues with new revisions; 'Whine' noise petition
- MacBook Pro Special Report follow-up #4: More on loose batteries, powering off
- MacBook Pro Special Report follow-up #3: Replacement units shipping with improved right speakers; Wake-from-sleep issues
- MacBook Pro Special Report follow-up #2: Cannot connect to LEAP networks
- MacBook Pro Special Report follow-up: More abnormal noises from some units
For more coverage, see our MacBook Pro special report.