Hearing this, we understand why the 4 detections of supposed pingers are considered by prudent people (and real scientists are prudent people) only as a good track and not a certainty:
Mysterious Duck-Like Ocean Sound-Source Revealed | Video | LiveScience
OK, it is not the right frequency nor a near one. But who knows if there is not another specie with a more pitched "voice"? The "mechanical" repetition of the sound is astounding!