Without knowing what camera settings were used in the photograph leaves a couple of possibilities.
#1 on my list is ISO speed. The T1i is a good camera, but is years behind current sensor capabilities. Being this is a low light shot, I'm guessing either you or the camera boosted up the ISO speed to get a reasonably exposed picture at a shutter speed sufficient to stop motion. Generally, with ISO speeds, the lower, the better. In my opinion, the T1i isn't known as a low light camera these days as it's best ISO speeds are probably 1600 and less. After that, the noise level approaches 'unacceptable' and only moderately correctable.
#2 on my list is the large dark areas in the image. Dark areas are another noise generator, especially when 'cranked up' in post processing, such as the Lightroom 'shadows' slider. I use the shadows slider frequently on my low-light photographs to brighten up peoples faces, etc.
#3 is that the images presented represent a significantly cropped image. In low light shots like this, most cameras will have some noise, but it's generally not visible when viewed as the entire image and not expanding it up to billboard size and seeing the noise.
Your profile says editing your photos is OK. I'll be the first to admit I am a self-taught hack when it comes to post processing, but I can usually come up with an acceptable result. So I took a shot at your photo. As this is a JPG image to start with, a good deal of the latitude in editing is lost. So, I played a bit with the sharpening sliders as well as noise reduction in lightroom (I'm a real hack at both...'played' is the correct word to describe my efforts) and used an add-on noise reduction product and came up with this in a couple of minutes.