On: Magnetoelectric antennas could transform how underwater robots talk

[zipy124]

Yup, on the order of below 100 Hz usually https://en.wikipedia.org/wiki/Extremely_low_frequency .

[fc417fc802 → zipy124]

Below a certain point do you suppose my headphone jack can double as a transmitter?

[ferdzo → fc417fc802]

Technically, yes. Also a lot of people in the amateur radio community use the microphone in as a receiver for VLF transmissions.