manometer

Maybe it's best to leave the definition of "manometer" to the imagination. Since I can hardly tell you what it is, if you don't already know that it's a device that uses a spinning mirror to indicate the effect that air pressure associated with the enunciation of different vowels sounds has on the stature of a gas flame. Makes a cozy illustration in a book whose title escapes me, and I won't fetch it now because the explanation I attempted above has me ready to snooze. Good night!