Where to look for "noise"
As I recall, he addressed the issue as "grainy"... and that is something you really should not notice in today's sensors (under "normal" illumination) unless they are malfunctioning.
If I were looking for minor defect, due to noise, all you have to do is blow up a solid, light colored area, with a bit of shadowing in it, and inspect it. The telltale speckled purple and green flecks will quickly tell you if you have a noise issue. Noise is supposed to be better controlled in the new sensors, so they say. To me, nothing beats a better exposure... add light, lower the ISO.
Grainy? That's something else, entirely. That is, more often than not, light starvation in both digital and film cameras. It can result in noise... but that is a side-effect... noise is generated by the sensor... as a substitute for what it cannot get from the light. Grainy looking stuff is just not enough light making to the sensor or the sensor just not being able to use it properly. I mean, they're close... but grainy is not generated by the sensor... it is the result of not enough photon information to create a salient image.
Again... I suggest a quick comparison between the two identical images (a330 & a65) would be telling, to a point.