Christoph Reuter, Univ.-Prof. Dr. (of the Institut für Musikwissenschaft, Universität Wien, Austria) has not only investigated the Psychoacoustics of Chalkboard Squeaking, he’s also associated with a unique experiment which looked at ‘stabile Seifenblase am Schalltrichter der Trompete’ [trumpet with robust soap bubble at the bell] which is shown here in this video :
NOTE: Improbable has not yet been able to find any supporting information regarding the results-of and motives-for this experiment — any suggestions gratefully considered.