the air molecules
a dildo wave
a transverse wave
A sine wave.
If the source of a wave is moving towards the observer, the observer will perceive a higher frequency (blue shift) in the wave. If the source is moving away, the observer will perceive a lower frequency (red shift) in the wave. This is known as the Doppler effect.
When a wave source is moving towards an observer, the pitch or frequency of the wave increases, known as a Doppler shift. This occurs because the waves are reaching the observer at a faster rate due to the source moving closer. Conversely, when the wave source is moving away from the observer, the pitch or frequency decreases.
The P-wave which is a form of body wave known as a compression or longitudinal wave.
The energy of a wave moves forward with the wave. A wave is moving energy, and the wave carries it in the direction of propagation.
That would be a P-wave or Primary wave which is a longitudinal seismic wave.
the air molecules
restposition
One factor of course would be how fast the wave is moving.
Constructive interference can be a confusing concept when called interference. It is wave interference that is moving in phase with another wave. This causes the waves to for a resultant wave with a greater amplitude. Destructive interference is wave interference that is moving out of phase with another wave. These waves form a resultant wave of lower amplitude.