Caution Ear Protection Area Thinkpad R50 / R51
Periodic Fan Noise - Fan Howling - pulsating fan noise

Störendes Lüftergeräusch, Lüfterheulen, pulsierender Lüfter

>> solved by IBM with Embedded Controller Program V3.03 (29.July.2004) <<

IBM Thinkpad R50  TJ07RGE  Model No 1829 7RG, Bios and Embedded Controller 11.May.2004 - Factory Default, Windows XP pro SP1
This MP3 audio file demonstrates 40s of  the fan howling at every 5th second approximately. You can hear the fan noise at two fan speeds (frequencies), as the fan is increasing its speed to cool at 100% CPU. The howling noise is clearly heard in quiet environments, and very disturbing indeed. (Turn up your speaker volume, if you do not hear anything.)

Download (280 KB) and listen to:

Ear-itating Noise

Now I've got a R51 which sounded the same compared to the R50 only that the pulsating fan noise was only appearing from time to time during normal operation. Overall it was an acceptable noise emission.
Hear the R51 cooling at 100%CPU with out-of-date EmbCtrlProg V3.01, original fan 13N5182:

Then I fitted the Long Fan M10 (13R2657) into a R51 with FireWire. This appeard simple first, and then got out of control somehow.  But the Long Fan M10 is really pleasing my ears now. :-)
>> report.

This is how a Thinkpad R51 can sound with a Long Fan M10 at 100%CPU:  near silent and no high frequencies:

This recording was made with ECP V3.03, but there is no audible difference to ECP V3.01, when Long Fan M10 is installed.

Feedback and solutions welcome at:
de.comp.sys.notebooks - Thinkpad-Lüfter pulsieren immer noch
last updated: 2.Aug.2004