Listening to the file audio you can hear a clock.

Let’s open it with Audacity and check if there’s something.

Audio waveform in Audacity of audio file with clock sounds

Apparently nothing.

But zooming in you can notice some irregualrities in the sound waves.

Zoomed in view of audio waveform showing irregularities

First thing I can think of is morse code

By decoding it we obtain the flag.

-> flag{h014_p33p5}