Final answer:
When an emergency vehicle approaches, you must pull over and stop to let it pass. The Doppler effect helps you determine the vehicle's approach and departure by the change in siren pitch, and when the vehicle is directly in front of you, you'll hear the siren's actual frequency.
Step-by-step explanation:
When you hear or see an emergency vehicle approaching from any direction while you are driving, you must pull over to the side of the road and stop, making way for the vehicle to pass. This is crucial as emergency vehicles, such as ambulances are often rushing to aid in situations where every second counts. The Doppler effect allows you to hear the pitch of the siren change as the ambulance approaches and moves away, indicating its direction and distance relative to your position. This acoustical phenomenon is marked by an increase in frequency as the ambulance comes closer and a decrease as it moves away, guiding you on when to safely pull over.
If you are standing at an intersection or on a sidewalk, the frequency of the siren you observe will most closely match the actual frequency of the siren when the ambulance is directly in front of you as there is no relative motion between you and the siren at that point. However, for someone with Doppleraphobia, minimizing the exposure to the Doppler effect might involve moving away from the path of the ambulance or finding a quiet, enclosed space.
In the hypothetical scenario where you are standing at the center of a park with a circular road around and an ambulance drives around with its siren on, the pitch of the siren will change continuously due to the constant change in distance and angle relative to your position, a phenomenon known as sound interference and resonance.