I found out this info about adding sounds for custom language: https://sangomakb.atlassian.net/wiki/spaces/PG/pages/20709972/PBX+GUI+-+Sound+Languages+User+Guide
It explains whole procedure but important part is missing: list of necessary prompts, text prompt for each and explanation of context they are used that would help record them properly.
I checked /var/lib/asterisk/sounds/en. There are quite a number of files, but from names it is not quite obvious what is their purpose, and many are quite obscure.
Do I have to make all sounds in my language or I can do those that are needed and let FreePBX use English ones for those that are not existing for my language? I mean, not to copy English sounds into my language sound pack but to keep my language sound pack “clean” containing just my language sounds and let FreePBX fall back to English if sound file is missing in my language.
Is there somewhere list of prompt phrases that are actually needed for everyday use?
That said, if I manage to make decent sounds for my language (that is not available in FreePBX), is there way to make it public for others to use?