That's an hypotesis just as many others. Investigators and medics who visited the patients say they don't know. Source : yesterday's arstechnica's article: https://arstechnica.com/science/2019/01/canada-halves-diplom...

The sound heard around some of the possible attacks may have been crickets, but that doesn’t explain the symptoms.

Could that not have been a sound effect (audio file) transmitted via a technology such as this?