This format extension is one of the Speex Audio formats. It is an open-source codec developed by Xiph.Org. Used for creating voice messages and transmitting voice over packet-based networks with a low level of security. It is an audio file with recorded voice messages that are packaged in an OGG file. Only certain media players can open it.

opus

Opus (formerly Harmony): an audio codec for lossy compression

This format was created for online broadcasting. Opus is an audio codec for compression used on the Internet in real-time mode. Employed by programs such as Skype and Mozilla. Mostly used in interactive applications. The advantages of Opus are high audio quality and good compression. It works only on devices powered by Windows. Opus files can be converted to similar extensions.