How we hear the Changes of frequency of sound?

We can hear the changes of frequency of sound by Pitch of the sound.

Explanation:

Sound waves have different parameters like Pitch, Loudness, Intensity etc. Any kind of waves consists of parameters like wavelength and frequency. So pitch is directly related to frequency. If the change in frequency is more, the pitch will be termed as high and if the change in frequency is low, the pitch will be low. So the terminology pitch is used for hearing the sound waves. While frequency is the parameter of the propagation or travelling of sound wave, pitch is the nature of change in frequency heard by the observer.