Replying to
@mlanger@mastodon.world @dec23k@mastodon.ie @tomsart@mastodon.social
There are microphones on the market that can record sounds below 20hz. Also with software such as audacity you might be able to change the pitch so other people can hear it. There also is spectrum analysis software out there to visualize anything you record.
Maybe get in contact with a local university as this equipment is most commonly used in research (as far as i know)