When something goes wrong on your Mac that causes it to send out a special warning sound but without a warning sound. Whether it's MacBook or iMac or MacPro, you know that something happens when the fan goes on. The culprit? Heat. The fans are in the Mac to keep the inner parts cool, but open Safari for a dozen web pages filled with animated Flash ads, and you'll hear the fans coming in soon enough, and sometimes it's loud. Very high.
How can you control the fan? OS X enables the fan to turn on automatically depending on specific temperatures, but the free Macs Fan Control app gives you a little more control over what's going on and when.
It looks like this.
What you get is real-time monitoring of Mac's fan speed and temperature sensors from the icon in Menubar.
You also get controls to set a constant value for any Mac fan. This can help resolve some noise issues, such as when replacing a Mac disk drive. Fans can also be controlled to a set speed relative to a specific temperature sensor.
Is more control better? Not necessarily.
Macs Fan Control gives you access to options that Apple really doesn't want you. Incorrect setting can cause your Mac to overheat, which can lead to failure of internal parts, so beware of the developer's warning that the app is for advanced users.