Metronom

[chilobo]

If there was a metronom exact enough to be synced between two smartphones another method of measuring the speed of sound would be possible:
Syncing the two metronomes one user visibly claps his hands synced with his metronom and walks away. He stops when the other user signals, that the visual signal is in sync with his metronom.

[Jens Noriʇzsɔɥ]

Rather than using two smartphones, two (wireless) speakers or earphones could similarly work. Utilizing speakers would not even require anyone to clap hands. However, bluetooth range might become an issue then.

[Jens Noriʇzsɔɥ]

While answering your post, I have been wondering if noise cancellation would work. Well, it has already been done: check https://twitter.com/DocWhalley/status/12...9078156290 and included references…