What does an altimeter respond to in order to measure altitude?

An altimeter measures altitude by responding to changes in atmospheric pressure. As a person ascends to a higher elevation, the atmospheric pressure decreases; conversely, when descending, the pressure increases. The altimeter uses this change in pressure to calculate the altitude above sea level. This is grounded in the principles of the barometric formula, which relates atmospheric pressure to altitude under standard conditions.

While the other options might play a role in aviation or meteorological conditions, they do not directly influence the primary function of an altimeter in measuring altitude. For example, vibrations in the air or wind speed adjustments do not provide a direct measure of altitude, and temperature variations, while they can affect air density and pressure, are not the primary mechanism by which altimeters gauge altitude changes. Therefore, the correct understanding of how an altimeter works is centered around its sensitivity to atmospheric pressure.