Part of me says, "How many other things sound like 37.5 KHz bursts at intervals of one second?"
But the news isn't really giving a feeling for what's actually happening, so I'm trying to imagine how this could be a mistake.
As ERD50 pointed out, we're not talking about guys actually hearing the pulses, there's got to be a device that, as in the video above, is beeping when it detects something of the right frequency.
Also, the ship that's listening probably doesn't have specialized equipment for black box pingers. They probably cobbled something together to beep whenever something close to 37.5 KHz rises above a threshold. Not hard to do, but perhaps a little primitive.
The news shows someone holding a microphone on a pole underwater. Remember that this ship isn't the one with a towable yellow bat toy.
So these guys are sitting in the hold of a ship, watching an oscilloscope, and waiting to hear their device beep. They set the threshold lower and lower, and occasionally get beeps from background ocean noise.
At some point, they start to hear some regular beeps. Just a few in a row, and not at a frequency of one per second, but they figure they are far away, so that some of the beeps are not detected.
They play with the threshold, figuring a very low signal to noise ratio, and get a lot more beeps, but they figure that some are valid pings, and some are background noise.
This is where their imagination comes into play, transforming a semi-random series of beeps into regular beeps hiding among the noise.
I know nothing about what's going on, but that's one scenario in which people could be fooled into thinking they "heard" pings when they didn't.
Let's hope they left the 8-track recorder on the second time.