Final answer:
The subject involves understanding the Doppler effect and how the frequency of a sound, like an ambulance siren at 500 Hz, changes for an observer as the source moves relative to them, with shifts in frequency being noticeable due to human hearing sensitivity.
Step-by-step explanation:
The question relates to the Doppler effect, a phenomenon observed when a sound source is moving relative to an observer. In physics, the Doppler effect explains why the frequency of waves, such as sound waves, changes based on the relative motion of the source and the observer. For example, when an ambulance siren emitting a steady frequency moves towards you, the frequency you perceive increases; as it moves away, the frequency decreases. If we consider an ambulance with a siren operating at 500 Hz at a small height above the ground, the frequency heard by an observer would shift higher as the ambulance approaches and lower as it moves away due to this effect.
An important aspect to consider is the speed of sound in air, which is approximately 340 m/s and varies with temperature, height above sea level, and the medium's phase. Using the Doppler effect formula, one could calculate the speed of the ambulance if its siren's emitted and observed frequencies were known. Additionally, humans can hear frequencies between 20 Hz and 20,000 Hz, and the smallest frequency shift that an average person can detect from a 500 Hz tone is part of understanding the sensitivity of human hearing.