Is there something seriously wrong with your notebook? I wouldn't call the SDS1104X-E noisy by test equipment standards, but those standards are pretty low. I have an X220 beside the scope right now, and the scope completely swamps the notebook.
It's something in between a hair dryer and a vacuum cleaner. I regularly use SDS5000s and they are *much* more silent than the 1104x-e.
Today, I tinkered with an old 1 GHz Agilent scope at the university. It's as deep as a CRT scope despite being digital, weighs a ton, and needs a lot of cooling. In terms of sheer sound pressure, maybe it's even a bit over the 1104x-e, but since the pitch is much lower (big fan), one finds it to be more bearable (but it worn me off after a while nonetheless).
The 1104x-e exhibits both high sound pressure and high pitch.
Pity, because it's a good scope. However, consider that the fan always run at maximum rpms, and is made to cool the scope under stress with 40C.
From my experience with small fans, if you run them at 9V rather than 12V, the difference in airflow and static pressure won't be dramatic, but the difference in acoustical noise could be substantial.