The pitch of an acoustic device can be increased by
Answer Details
The pitch of an acoustic device refers to how high or low the sound is perceived by the human ear. It is directly related to the frequency of the sound wave. Therefore, to increase the pitch of an acoustic device, we need to increase its frequency. Thus, the correct option is "increasing the frequency".
Increasing the amplitude of a sound wave would make it louder, but it would not affect the pitch. Similarly, decreasing the loudness would not affect the pitch either. Finally, decreasing the intensity of a sound wave would make it less powerful, but it would not affect the pitch either.