Install asterisk-core-sounds-en-gsm by entering the following commands in the terminal:
sudo apt update sudo apt install asterisk-core-sounds-en-gsm
asterisk PBX sound files - en-us/gsm
Asterisk is an Open Source PBX and telephony toolkit. It is, in a sense, middleware between Internet and telephony channels on the bottom, and Internet and telephony applications at the top. . Asterisk includes a set of standard sound files in various formats. This package contains the core part of that collection in English (US, by Allison Smith) in raw gsm-fr format (Compressed. Takes relatively little space. playable with sox).