is there anyway to get rid of hiss sound on t3i?

[skratch]

i tried the the whole changing it to manual and turning rec level down but all that does is is lower the volume for the audio the camera picks up, my external mic also has the same hiss, do other canon cameras also have this hiss cause im also interested in upgrading from the t3i

[Waddizzle]

If you're hearing the his only during "silent" portions of audio, then what you're hearing is the probably the effects of audio compression at work. 

Any audio recording system has a limit to the amount of dynamic range, the difference between the loudest and quietest sounds, that it can handle.  A compression circuit boosts the gain when the audio is relatively quiet, below a certain threshold, and reduces the gain when it goes above a certain threshold, functioning as a limiter.

The net effect of dynamic range compression can be an apparent increase in background noise.

[TCampbell]

There are limits to what you can do with the audio quality of a built-in condenser mic.  You can get improved sound quality by using an external mic.  Rode makes the "VideoMic" series of microphones which mount to the camera hot-shoe (they don't use the hot-shoe for anything other than a way to attach the mic to the camera -- a separate cord attaches it to the microphone jack on the side of the camera body.)