There are various metaphone algorithms that produce an encoding that handles these cases, at least for English and some of the other European languages from whi

There are various metaphone algorithms that produce an encoding that handles these cases, at least for English and some of the other European languages from which words and names have made there way into English. The "fancy trick" is basically that search still works pretty well if you just throw away all the vowel sounds - your examples of "mueller" and "Müller" both encode as: MLR https://en.toolpage.org/tool/metaphone https://en.toolpage.org/tool/metaphone