Having an electric motor, it is almost silent when running on battery power and still is extremely quiet even after switching to gas - powered operation. (autolist.com)
I found this speech recognition implementation responsive, even when running on batteries, but the text did not always match my speech precisely. (tabletpcreview.com)
This unit is small and compact, and can also run on batteries for a few nights when you want it to, making it a good travel companion. (whitenoisemagic.com)