Let's say you have a sound emitter and receiver a fixed distance apart on a moving object but open to the air, such as on the hood of a car. The emitter is near where the windshield wipers are, and the receiver is closer to the grill. They are in aligned along middle of the car, longitudinally. I understand that if the emitter outputs a constant frequency signal, the receiver will hear that same frequency no matter what fixed speed the car is travelling at. My question is, what about during acceleration? At any point in time, the receiver is hearing the output from the emitter x time in the past because the sound has to travel the distance they are apart. So if you are at rest and you slam on the accelerator, the receiver will still be seeing the waves from the "stationary" emitter for x time while moving at a higher speed, therefore creating a Doppler effect. Is this thinking correct? Thanks in advance!