I partially solved the problem using i8kutils. Here's a guide about it:

Keenformatics - How to solve Dell laptops fan issues in Ubuntu

and a discussion here on askubuntu:

Dell Inspiron 5521 i7-3317U Fan CPU too Noisy

Here are the main steps as written on Keenformatics site (my blog).

How To solve Dell laptops fan issues in Ubuntu

1. First of all, let's download and install i8kutils. Open your terminal and write:

   sudo apt-get install i8kutils

2. Now you've got to add i8k to your modules. Open the modules file:

   sudo gedit /etc/modules

   and add the string "i8k" (without quotes) to the file. Save and exit.

3. Create an i8k.conf file

   sudo vim /etc/modprobe.d/i8k.conf

   and fill it with this code:

   options i8k force=1

   Note: Some older guides will tell you to create a /modprobe.d/options file. The "options" file isn't used anymore on Ubuntu. What does matter is that you create a file with a .conf extension (the filename isn't important, but I decided to name it i8k.conf for clarity). So beware of older i8kmon configuration guides.

4. Now restart your computer, or run this code to make i8k run:

   sudo modprobe i8k force=1

5. We will now create a i8kmon.conf file which will tell the i8kmon utility how to behave.

   sudo gedit /etc/i8kmon.conf

   Paste the following code in it:

   # Run as daemon, override with --daemon option
   set config(daemon)      0
   
   # Automatic fan control, override with --auto option
   set config(auto)        1
   
   # Report status on stdout, override with --verbose option
   set config(verbose) 1
   
   # Status check timeout (seconds), override with --timeout option
   set config(timeout) 20
   
   # Temperature thresholds: {fan_speeds low_ac high_ac low_batt high_batt}
   set config(0)   {{-1 0}  -1  40  -1  40}
   set config(1)   {{-1 1}  30  60  30  60}
   set config(2)   {{-1 2}  53  128  53  128}
   
   # For computer with 2 fans, use a variant of this instead:
   # Temperature thresholds: {fan_speeds low_ac high_ac low_batt high_batt}
   # set config(0) {{-1 0}  -1  52  -1  65}
   # set config(1) {{-1 1}  41  66  55  75}
   # set config(2) {{-1 1}  55  80  65  85}
   # set config(3) {{-1 2}  70 128  75 128}
   
   # end of file
   

   This has been edited to match my Dell Inspiron 15r 5521 fan configuration (and I hope I did it well). If you want more informations take a look at the documentation on Ubuntu Manuals: http://manpages.ubuntu.com/manpages/gutsy/man1/i8kmon.1.html

6. Now you should be able to run i8kmon from your terminal and see if (and how) it's working. Simply run:

   i8kmon

Finished!

I don't think you need to control fan speed, actually fan should not make much sound even at high speeds.

If you look at the output of sensors command for my dual-core computer and compare it with yours, you'll find that the fan speed your computer is using is keeping your processors cool, which is important.In my case the processor temp are high but fan speed is low.

Adapter: ISA adapter
Core 0:       +74.0°C  (high = +76.0°C, crit = +100.0°C)
Core 1:       +67.0°C  (high = +76.0°C, crit = +100.0°C)

w83627dhg-isa-0a10
Adapter: ISA adapter
Vcore:        +1.10 V  (min =  +0.00 V, max =  +1.74 V)
in1:          +1.26 V  (min =  +0.05 V, max =  +0.23 V)  ALARM
AVCC:         +3.36 V  (min =  +2.98 V, max =  +3.63 V)
+3.3V:        +3.38 V  (min =  +2.98 V, max =  +3.63 V)
in4:          +1.26 V  (min =  +0.02 V, max =  +0.36 V)  ALARM
in5:          +0.78 V  (min =  +1.16 V, max =  +1.86 V)  ALARM
in6:          +0.88 V  (min =  +0.28 V, max =  +0.02 V)  ALARM
3VSB:         +3.39 V  (min =  +2.98 V, max =  +3.63 V)
Vbat:         +3.31 V  (min =  +2.70 V, max =  +3.30 V)  ALARM
fan1:           0 RPM  (min =  405 RPM, div = 128)  ALARM
fan2:        1110 RPM  (min = 6490 RPM, div = 8)  ALARM
fan3:           0 RPM  (min = 1054 RPM, div = 128)  ALARM
fan4:           0 RPM  (min = 10546 RPM, div = 128)  ALARM
fan5:           0 RPM  (min = 10546 RPM, div = 128)  ALARM
temp1:        +38.0°C  (high = +64.0°C, hyst = -43.0°C)  sensor = thermistor
temp2:        +58.0°C  (high = +80.0°C, hyst = +75.0°C)  sensor = diode
temp3:        +42.5°C  (high = +80.0°C, hyst = +75.0°C)  sensor = thermistor
cpu0_vid:    +0.000 V
intrusion0:  ALARM

aditya@aditya-desktop:~$ 

I'll suggest you to check if the hardware installation of fans is correct(either yourself or from some expert). The sound should vanish by little bit tweaking.If it doesn't work then you may consider decreasing the fan speed by using fancontrol

WARNING
Please be careful when using the fan control features of your mainboard, in addition to the risk of burning your CPU, at higher temperatures there will be a higher wearout of your other hardware components, too. So if you plan to use these components in 50 years, maybe you shouldn't use fancontrol at all. Also please keep in mind most fans aren't designed to be powered by a PWMed voltage. In practice it doesn't seem to be a major issue, the fans will get slightly warmer, just be sure to have a temperature alarm and/or shutdown call, in case some fan fails, because you probably won't hear it anymore ;)

How to use Fancontrol

• First install fancontrol

  sudo apt-get install fancontrol
  

• Use pwmconfig, an script to manage fancontrol

  pwmconfig
  

  Now follow the instructions to configure your fan speed.