Some time ago I sent a guide to identifying strange sounding signals. Here it is again with a couple of other very good sources. - Bill W2CQ
Signal Identification Guide
https://www.sigidwiki.com/wiki/HF
http://www.w1hkj.com/Modes/index.htm
— make sure to use the menu on the left-hand side.
https://kv5r.com/ham-radio/digital-modes/sounds-of-the-digital-modes/
https://www.sigidwiki.com/wiki/Signal_Identification_Guide