Remember this gem

[pucho812]

A prototype horn loudspeaker driven by compressed air and an "artificial larynx" used as a portable public address system in Los Angeles, California, USA in 1929. The inventors tried to imitate human vocal cords. It could reportedly project voice or recorded music 4 miles. A vacuum tube audio amplifier powered 4 "artificial larynxes" which modulated compressed air going into the horn provided by a 50 HP gasoline engine and compressor. The owners rented out the powerful system for $300 per hour.

4 miles? At what spl up close? Says music and speech so what frequency response? Also 300 dollars an hour in 1920’s money is nothing to sneeze at...


https://www.americanradiohistory.com/Archive-Radio-News/20s/Radio-News-1929-05.pdf
https://commons.wikimedia.org/wiki/File:Horn_loudspeaker_truck_1929.jpg

 

[cyrano]

The US military built a set of large shipping containers, one containing the speakers, the other the amps and control room, able to "project" sound at large distance for crowd control. I seem to remember it could do 120dB SPL@ 20 Hz a quarter of a mile away.

When googling around, I noticed that it wasn't one try. There's at least dozens.

https://scienceandglobalsecurity.org/archive/sgs09altmann.pdf
In Sweden in the eighties, they tried demolishing buildings with infrasonic sound. While they were able to demolish the test building, it never reached commercial application.