# 1
Multiple Choice
When an ambulance with a siren passes by you, the pitch of the sound seems higher as it approaches and lower as it moves away. What causes this change in pitch?
When an ambulance with a siren passes by you, the pitch of the sound seems higher as it approaches and lower as it moves away. What causes this change in pitch?
Change in loudness
Change in air temperature
Echo from nearby surfaces
Change in frequency due to relative motion
