As you run toward a source of sound, you perceive the frequency of that sound to decrease.
Step-by-step explanation:
Doppler's effect is a principle used to describe the frequency and the intensity of sound and wavelengths of a source and observer with the two possibilities.
(i) Stationary sound source and moving observer.
(ii) Moving sound source and a stationary observer. It is a relative motion.
Consider when the observer is moving towards a source, the frequency of the sound will be higher and when moving away from the source, the frequency will decrease.