The frequency of the sound produced by a siren increases from 400 Hz to 1200 Hz while its amplitude remains the same. Therefore, the ratio of the intensity of the 1200 Hz wave to that of the 400 Hz wave is

A

$$1 \colon 1$$

B

$$3 \colon 1$$

C

$$1 \colon 9$$

D

$$9 \colon 1$$