Hi nishachandran84 and welcome to Dell Forums.
Since no one has answered you, I am going out on a limb here.
I am guessing you are using Skype (another messenger application). It has a special effect voice sound option to fool around. Check in sound option/microphone.
If not, it could be a wrong audio driver. See here:
Since you do not say what OS you are running in your laptop, You can choose the driver here:
Hope it helps.
Dim9200/XPS 410.C2D 2.40GHz.2GB RAM.XP Pro_86 SPk3. IE8 & FF38
Avast!Free 2015. CIS 5.12(FW/D+). MBAM Premium. MCShield. WinPatrol +. WOT. OpenDNS. SAS(o/d)
"We are all ignorant, but we don't all ignore the same things..." Albert Einstein
"When you've excluded the impossible, whatever remains, however improbable, must be the truth..." Sherlock Holmes.
Here is a suggestion in addition to iroc9555's advice. Other posters have referred to audio effects that alter the sound through the mic. See if they are turned on and disable them. See if you can find them by following this path:
Start>Programs>Dell Webcam>Laptop Integrated Webcam>Dell Webcam Console
Look for a tab on the top left saying "effects", under "audio effects" and unclick the enable box. (This path was originally posted by forum member AbbyCharlotte.)