Actually, in-camera noise reduction (the kind you can turn on and off) is applied only to exposures of 1 second or more. However, part of the camera's conversion of RAW data to jpg does incorporate a dose of automatic NR. In fact, the conversion algorithm is an important factor in the presence of noise and the choice of converter can be significant. However, any good converter nowadays allows user selected changes to some varibles in the algorithm in order to adjust noise reduction, even DPP in a somewhat primitive fashion. As always, however, there is a trade-off between sharpness and detail extraction on one hand and smoothness and blurring on the other. And, of course, any sharpening applied by the converter will also influence noise. So to sum up, you should tell us more details about the exposure itself and the RAW conversion you did.