The reason that a police car's siren sounds HIGHER in pitch as it approaches you, is because the truck pushes the sound waves together so that the sound wavelengths in front of the truck gets shorter. This
causes the
A
Frequency to increase, which increases the pitch
B
Velocity to decrease, which increases the frequency
C
Frequency to decrease, which decreases the pitch
D
Wavelengths to get longer, which increases the pitch

The truck pushes the sound waves together so that the sound wavelengths in front of the truck get shorter. This causes the frequency to increase, which increases the pitch.

What is wave frequency?

The number of waves that pass a specific place in a given length of time is known as wave frequency. Hertz (Hz) is the SI unit for wave frequency,

A higher-frequency wave with the same amplitude has more energy than a lower-frequency wave.

The truck pushes the sound waves together so that the sound wavelengths in front of the truck get shorter. This causes the frequency to increase, which increases the pitch.

Frequency is directly propotional to the pitch. Option A is correct.

Hence this causes the frequency to increase, which increases the pitch.

To learn more about the wave frequency refer to the link;

https://brainly.com/question/14316711