At the Wernerwerk plant in Siemensstadt, Weber worked to improve speakers and microphones for telephone systems. In 1911, when he started developing his “apparatus for the hearing impaired,” electric hearing aids from other manufacturers were already on the market, but they were very large, making them both heavy and noticeable. When designing his hearing aid, Weber was careful to focus not only on improving sound quality; the device, as he said, was also supposed to be “as small as possible, so it is not very bothersome to the wearer.” After numerous attempts, he succeeded in producing a highly sensitive carbon microphone, two of which he combined with a small receiver and a three-volt battery to make an “apparatus for the hearing impaired.” Weber took his device to Mr. Kloenne with the aim of “helping him with this apparatus where other attempts had failed [...]. But to no avail again.” After that, Weber made “one last desperate attempt”: He had a double headphone made in the place of the single headphone that had been used previously, and set off to see Kloenne again. When Kloenne saw the double headphone, he said there would be no point in trying it, since he was completely deaf in one ear. Weber was finally able to convince him to try the device after all, and “lo and behold, Mr. Kloenne was now able to hear even in the ear he had thought was deaf, and he beamed at this success.” Later, he noted, “I fondly recall the day when Mr. Kloenne told me, visibly moved, that the new hearing aid had allowed him to participate in a group again for the first time in a long while.”
After Weber’s successful development, Siemens & Halske decided to market hearing aids under the name Esha-Phonophor. “Esha,” pronounced “es-ha,” mirrored the German pronunciation of S&H, the abbreviation commonly used for the company name at the time. The unit was launched on the market in late 1913, in several versions. In one configuration, a special ladies’ version, the microphone and battery were held in a purse. Another version took the form of a folding camera, a popular accessory at the time, complete with a discreet leather carrying strap. Hearing loss sufferers were also able to choose from one, two, or even four microphones right from the start, for a configuration accommodating their individual level of hearing loss.
Weber’s technology stayed in use for a long time, albeit in a revised form and with better materials. One year after the Phonophor, Weber developed a small device he called an “ear telephone,” which was used as a receiver for switchboard operators. This earphone, affectionately known as the “hazelnut” due to its shape, was outwardly very similar to modern in-ear headphones, featuring a diaphragm made from an animal eardrum. Not long afterward, the headphone was offered as an alternative in newer Phonophor model series. After Siemens & Halske employees learned that famed X-ray inventor Wilhelm Conrad Röntgen was losing his hearing, they presented him with one of their new models as a gift in 1922.