JF Ptak Science Books Post 1926
From the looks of it, this image from an 8 April 1933 issue of the Illustrated London News is not quite a "verbal bomb" as we might think of such a thing today. The cutaway drawing (by the sensational G.H. Davies, who produced hundreds of these images for the magazine over four decades)shows an acoustic device housed in a Vickers Victoria aircraft. As described in the descriptive text to the image, Sir Philip Sassoon ("speaking in the House of Commons on the Air Estimates last month") mentioned in May 1933 an attempt to induce forces hostile to the U.K. in Northern Kurdistan by flying over rebel strongholds and threatening an air attack if no surrender was forthcoming.
Evidently a translator would address the town at 2-4,000' elevation through an audio system that amplified the voice"1,600,000 times". An address was made to the leaders of the tribesmnen to surrender their position, else an air attack would occur after three days. Even though described in the title of the image as a "verbal bomb", it isn't anything like the directed energy/sonic/acoustic/infrasonics/pulse weapon performance degraders that are currently available. What was happening here was simply (or not so) an attempt to get an enemy to relieve their position via tangible threat, sort of an acoustic leaflet bombing prior to the real thing. Of course this was backed up by actual bombing, which was still a relatively new weapon for armies--several nations which possessed this newish facility of war practiced bombing civilian/military targets alike in extra-territorial possessions. (There was a hot debate over what constituted fair use of aerial bombs beginning in earnest in the 1920's, but much of that soon devolved into debates on what constituted "civilian populations", and there the definitions were wide and sloppy.) In any event, the loudspeakers did not emit high-powered sound that would disturb/puncture eardrums or cause dizziness or problems with eyesight by making the eyeballs vibrate--they were just loud conveyers of Bad Things to Come.