The Amazing Accelerometer. Single Unit (about $4). Which way’s up?. http://www.youtube.com/watch?v=KZVgKu6v808#t=246. Basis of the Technology. Another view. Biomedical. Automotive. Guidance/Navigation. Structural Health Monitoring. Sports Medicine: Concussions. FitBit and Nike Fuel.
If not designed properly, phase lag causes the measured signal to deviate from the actual acceleration. (Above example would be for a BAD design.). Ideally, you want to design for zero phase distortion.
Dynamic viscosity of air
Squeeze Film Damping: Thin film of air interacts with silicon masses in motion