The May 21 1927 edition of the Toronto Globe contained two separate ads for products that claimed to allow the deaf to hear.
The first was what today we would call hardware-related:
The Phonophor appears to have been manufactured by Siemens. In 1927, the Dictograph Products Corporation was at 11 Wellington Street East; by 1932, they had moved across the street to 9 Wellington West. By 1935, they were no more.
The second option for the deaf involved a patent medicine:
Catarrhozone appears to have been an inhaler. It apparently not only cured deafness, but overcame a variety of other diseases! It was manufactured by the Catarrhozone Company of Montreal. A search turned up: