In Germany Maximilian Negwer founded the company "Fabrik pharmazeutischer und kosmetischer Spezialitäten Max Negwer" in 1907. The first package of Ohropax noise protectors was sold in autumn 1908 for one Goldmark (adjusted for inflation about €5.75).[…]   
In August 1914, the product was recommended by Lieutenant General Freiherr von Dinklage to the War Ministry for use in the military. In 1916 the military introduced Ohropax. This was the first time that large sections of the population got to know the product, making Ohropax noise protectors the company's main product.  
<sub>Source: [Ohropax][1] & [Siegeszug von Ohropax begann im Ersten Weltkrieg][2]</sub>

[This video][3] shows Hermann Göring unplugging these protectors after he landed his plane during the last year of the First World War.

Plain and simple hearing loss and symptoms ranging up to shell shock are listed as reasons for introducing them. Previously it seems that communication ability, even if it required extremest forms of shouting were preferred and just covering the ears with your hands the only option available, despite age old stories about Sirens and Ulysses.


  [1]: https://de.wikipedia.org/wiki/Ohropax
  [2]: https://www.welt.de/gesundheit/psychologie/article130815520/Siegeszug-von-Ohropax-begann-im-Ersten-Weltkrieg.html
  [3]: https://youtu.be/U2UvGfsKHx0?t=1380