Talk:Hemispherical resonator gyroscope

The Hemispherical resonator gyroscope is often called "the wine glass gyro". To see why, take a fine crystal wine glass, "ping" it with your finger, and note the clear, resonating ring. Then, hold the wine glass next to your ear and "ping" it again while "twirling" it about the stem. Note that the tone increases and decreases as the wine glass is rotated. This tone increase and decrease is caused by a doppler effect as the maximum and minimum points on the resonating wine glass pass your ear. In more detail: When the wine glass is "pinged", the glass begins to resonate. The point on the glass, where you "ping" it, resonates the MOST. It sets up what's called a "standing wave" on the rim of the glass. The point where you "ping" the glass becomes the maximum and minimum point of the vibration standing wave. A similar maximum and minimum, is setup directly opposite from your "ping" point...as well as the points 90 degrees to the left and right, of the "ping"point. In other words the points on the glass that are creating the sound you hear are at the 4 "compass points" determined by where you "ping" it. When you twirl the glass, you are hearing the doppler effect as those 4 points of maximum sound creation, pass your ear, somewhat like the tone change when a train comes toward you then goes past. What was discovered, many years ago, was that when you ping a glass, and twirl it, the 4 points of maximum and minimum on the surface actually MOVE left or right from the "ping" point, along the glass rim, depending on which direction you rotate the glass. If you twirl the glass clockwise, the pattern moves to the left of the ping point. If you twirl it counter-clockwise, the pattern moves to the right of the ping point. This is called precession and is analogous to the movement of a spinning wheel gyro when you attempt to rotate it. If electrical sensors are placed on the surface of the wine glass, those sensors could be used to sense the direction, left or right, that the maximum and minimum points of vibrations move.