Siemens expanded hearing aid production after the huge success of the first Phonophor models. The aids were produced at Berlin’s Wernerwerk plant. New speaker and microphone technology made the new instruments easier to use and sound better. The new Phonophor was also smaller and lighter. Demand increased beyond Germany and several thousand units were being sold annually in the U.S. alone.
“You don’t have to suffer from hearing problems anymore! Try our Phonophor electric hearing aid, approved for years by many hearing loss patients. Now with an earphone that has been significantly improved after extensive testing and research.”
In 1924, an optional microphone amplifier was launched for those with especially severe hearing impairments. Starting in 1928, the metal microphone casing was replaced with a new type of plastic, called Bakelite, that reduced the weight. Siemens hearing aid consultants of the time had many of the same responsibilities as today's hearing aid providers. They helped consumers choose the right model, get used to hearing well again, and explained how to use it.