From the NPR report on the Xinhua story:
We'll caution that the signal hasn't yet been investigated, and it's too early to draw a connection to the missing flight MH370. The signal's frequency is 37.5 kHz, according to Xinhua. That's the frequency underwater locator beacons use to transmit their location; it's also reportedly used by other systems.
I thought that 37.5khz was chosen partly because it was unique.