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What is the MacBook Moo!?

Many users have observed that their Apple MacBook makes a mooing sound. The mooing sound is caused by the fan starting up and then immediately stopping over and over again. You can listen to a recording of the moo here, or view a video of a disassembled MacBook mooing here. The noise becomes very annoying when using the MacBook in a quiet environment and as yet Apple have not admitted this is a fault or produced an update to change the behaviour of the fan controller.

MacBook SMC Firmware Update - 17th August 2006

An official fix has been released by Apple! "The SMC Firmware Update adjusts fan behavior in the MacBook."

I have just installed this update and found that the fan is on (its lowest setting) even though the system temperature is only 51 degrees Celsius. So the fan behaviour has definitely been changed and will hopefully mean no more mooing! Whether it is merely a coincidence that the fix has been released in the same week I brought this to the attention of senior executives at Apple I do not know. Many thanks to all of you that signed the petition, I am sure together we made an impact on this.

MooFix Widget

I noticed that the mooing noise only happens when the processor is between 65 and 67 degrees Celsius, the annoying thing being that this seems to be the temperature at which the processor idles at. If the temperature rises slightly above this then the fan will come on constantly at its lowest speed. This is far less noticeable than when the fan is repeatedly turning itself on and off (a.k.a. mooing)!

I created a Dashboard Widget that monitors the CPU temperature and when it enters the "mooing zone" (65C - 67C) it increases the CPU temperature by a couple of degrees so that the fan stops mooing and stays on constantly. See the FAQ for details of how it does this. The widget can be turned on or off easily using the icon placed on your dashboard.

This is a rather crude fix to the problem and I hope it is only temporary. If you also experience the mooing problem and would like to see it fixed by Apple (hopefully in a simple firmware update) then please fill in the petition below.

Update 17-08-06: Apple has released an offical fix, (please see above).


So far I have not had much success in getting Apple to recognise the "mooing" as a problem and I need your help. If you also experience the problem with your MacBook please fill out the form below. I will then be able to approach Apple again with evidence that a number of people are not happy about this problem and want to see it fixed!

Update 17-08-06: Apple has released an offical fix, (please see above).

Note: None of the fields are compulsory, complete as little or as much information as you want. Your details will not be shared with anyone except for Apple Computer, Inc.

There are signatures so far.

First Name:
Last Name:
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Install MooFix Widget

Step 1.

You need to install CoreDuoTemp (version 0.9 or higher) for the MooFix Widget to work. This is because it relies on the SpeedIt framework by Increw Team and CoreDuoTemp does a nice job of installing this.

Step 2. Install the MooFix Widget. (If you use Safari the widget will be loaded automatically after the download completes.)

Current version: 0.1

How to use: To enable or disable MooFix simply click the icon on your dashbaord. When the red cross is shown MooFix is active.


Check out the forum for discussions related to the MacBook Moo problem.


Here are some comments from frustrated users:

"I plan on buying a Macbook, but only once this issue is resolved, until then I'm keeping my money." James Allen-Robertson

"My friend and I bought ourself MacBooks (one white and one black) They both moo together like a cow choir. It is just dreadful to listen to." Will Arentz

"It is the BIGGEST annoyance about the machine, its such a stupid thing that drags an otherwise brilliant machine down. PLEASE ADDRESS the issue at least." Chan Tiller-Cordy

"Just received my black macbook 4 days ago and thought that the sound was a cell phone vibrating somewhere. By the time I decided to start looking for it it would stop. Glad to realized that it is this mooing sound from the macbook... I thought I was going crazy because my cell phone was not set on vibrate!" Connie Smith


It would be great to hear your thoughts and comments. If you have any suggestions on how to improve the widget please e-mail me at jon@moofix.com.

Jon Smith