Several users have reported MacBook fan behavior similar to the lamented noise generated by the MacBook Pro (see the MacBook Pro special report) where the fan kicks on then suddenly off, generating what many users have described as noise akin to the "mooing of a distant cow."
With the use of the freeware utility CoreDuo temp, several users have noticed that the "mooing" fan noise only seems to occur when temperatures rise above 67 degrees celsius. In fact, one user (Yongwon Lee) has posted a video of a partially disassembled MacBook, demonstrating that the fan turns on at 67 degrees celsius, and back off as the temperature drops slightly.
Mark O'Brien writes:
'I received my MacBook yesterday (2.0GHz, 120GB HD, 2GB RAM) and have exactly the same mooing sound. The video you linked to shows exactly what I'm hearing when the computer is sitting idle at my desk. Peak sound occurs about every 7 seconds. I'll download the Core Duo Temp app tonight and see what the readings are when the fan cycling occurs."
One reader writes:
"I recently bought a MacBook from Amazon and I am currently experiencing the same problem as your users are. I have a (1.83Ghz, 100GB HD (7200rpm) and, 2GB RAM) both upgrades were made after the purchase. I did have the 'mooings' sound prior to upgrading those two components. The Moooing sound comes only when I plug in the AC adpater. I have discharged my unit twice. If I put it on 'Better battery life' setting, I still get the mooing sound, but not as often as 'Better performance'"
High-pitched noise emanating from power adapter Some users have also noticed a high-pitched noise coming from the MacBook's power adapter.
MacFixit reader Ian Brown writes:
'I recently purchased the new MacBook. I let the battery totally discharge prior to charging it the first time. I plugged in the power adapter to charge the battery and continued to use the MacBook, but I noticed a high pitch scream from the power adapter that changed pitch whenever the disk drive was accessed, presumably due to increase load. The noise is reminiscent of old switch mode power supplies."
MacFixIt reader Garrison adds:
"Two days after purchasing a new 1.83GHz Macbook, the power supply has begun to gurgle and hiss. We've tried it in different outlets, but as long as the laptop is being used while it charges, the sound is constant: a low-pitched electric hiss that is plainly audible in a quiet room with the brick 5' away. When the laptop is powered down, the hiss disappears, even though the red light on the magnetic connector indicates that the unit is charging."Fixes
Turn on iSight Several readers have reported that turning on the MacBook's built-in iSight eliminates the whining noise.
Adjusting screen brightness In one variation of the problem, the sound can be eliminated by turning screen brightness to the maximum level, though in-house we found that doing so resulted in emission of a different, yet equally annoying high-pitched noise.
Try tilting the display back and forth a few times Several readers have reported that tilting the display back and forth, or gently squeezing on the screen casing's lower left corner eliminates the noise.
Turn off one processor core Though not a viable long-term solution, some users have found that turning off one of the MacBook's processor cores eliminates that noise.
In order to turn off one processor, you need to install Apple's Developer Tools (from the install discs included with your MacBook Pro). You will then have access to a System Preference pane labeled "Processor" that can toggle between single and dual-core operation.
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