# Why does a siren on an ambulance sound higher pitched as it approaches you?

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## Why does a siren get louder as it approaches you?

So why do we hear a change in pitch for passing sirens? The pitch we hear depends on the frequency of the sound wave. A high frequency corresponds to a high pitch. So while the siren produces waves of constant frequency, as it approaches us the observed frequency increases and our ear hears a higher pitch.

## What scientific principle causes the sound pitch of an ambulance siren to get higher as it approaches you and lower as it moves away from you?

The Doppler effect occurs for all kinds of waves. It happens when either the source of the waves or the receiver of the waves is moving. The picture shows that the sound waves get compressed as the car moves toward you, creating a higher pitch sound.

## Why does an ambulance siren sound different when it comes closer?

As the ambulance moves away from you, the distance between you (the observer) and the siren (source of the sound) increases. Therefore, the sound waves get to spread out in a bigger area, thus making you feel as if the siren sounds low-pitched, or just different!

## Why does a siren change pitch?

The pitch of the siren of a Fire truck appears to change as the truck passes us due to the Doppler effect. … Since the speed of sound in air is essentially fixed, the perceived pitch of a tone is related to the wavelength of the sound. The shorter the wavelength, the higher the pitch, and vice-versa.

## When an ambulance is driving towards you the siren will sound?

Sound is a longitudinal pressure wave. As the ambulance moves closer to you, the air molecules get compressed together. The wavelength of the sound (these pressure waves) decreases, and the frequency increases. That results in a higher sound pitch.