Hi Guys ,

I am new to ubuntu 10.10 and I like to lower the CPU fan rpm from 1500 to 1000 so its less noticeable . I am sure its possible because I used it in Windows with speedfan Program .
Motherboard : Asus M4A79T Deluxe , CPU : Phenom II x4 955 , CPU fan : Cooler Master V8 .

When I type sensors in terminal I get this :

k10temp-pci-00c3
Adapter: PCI adapter
temp1: +40.6°C (high = +70.0°C, crit = +70.0°C)

atk0110-acpi-0
Adapter: ACPI interface
Vcore Voltage: +1.00 V (min = +0.85 V, max = +1.60 V)
+3.3 Voltage: +3.50 V (min = +2.97 V, max = +3.63 V)
+5 Voltage: +4.97 V (min = +4.50 V, max = +5.50 V)
+12 Voltage: +12.36 V (min = +10.20 V, max = +13.80 V)
CPU FAN Speed: 1580 RPM (min = 600 RPM)
CHASSIS FAN Speed: 0 RPM (min = 600 RPM)
CHASSIS FAN 2 Speed: 0 RPM (min = 600 RPM)
CPU Temperature: +38.0°C (high = +60.0°C, crit = +95.0°C)
MB Temperature: +39.0°C (high = +45.0°C, crit = +75.0°C)

And if the answer is codes in terminal please explain extra because I am not good at linux terminal yet ...

I think that this is what you are searching for.
Keep in mind that manually controlling the fanspeed needs monitoring the temperatures, or you can overheat your system.