A source ($$S$$) of sound has frequency 240 Hz. When the observer ($$O$$) and the source move towards each other at a speed $$v$$ with respect to the ground (as shown in Case 1 in the figure), the observer measures the frequency of the sound to be 288 Hz. However, when the observer and the source move away from each other at the same speed $$v$$ with respect to the ground (as shown in Case 2 in the figure), the observer measures the frequency of sound to be $$n$$ Hz. The value of $$n$$ is ______.