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.

ac3

AC3: a Dolby Digital audio file

This is an audio file extension that allows for achieving surround sound. It is utilized in files of the DVD format. Its manufacturing company is Dolby Digital. An AC3 file is an audio stream that can be encountered as external soundtracks for films. You can download it separately and synchronize it with the movie file. The audio file contains 6 channels: upper and lower, front and rear, right and left, as well as low-frequency effects.