The hissing noise immediately got louder. Curious, he kept rotating the knob until it stopped turning, but all that seemed to accomplish was to increase the volume. He set it back to where it had been and turned his attention to the other knob. This one made the glowing light change to a different pattern, although the hissing noise remained unchanged. Turning the first knob all the way in the quiet direction made the glowing light go out and the hissing stop.