Answer:
Pitch decreases
Step-by-step explanation:
The number of oscillation or number of vibration per unit time is called the frequency of a sound wave. The frequency of sound wave is also called the pitch of the wave. It is denoted by f or
. Its SI unit is hertz or Hz.
The speed of the sound wave is given by :

It is clear form the above expression that the pitch of the sound wave is inversely proportional to the wavelength.
So, when the wavelength of a sound wave increases its pitch decreases.