No audio transmitted and received and mumble-audio-player play no sound

When I run mumble-audio-player, I can connect the mumble-server, but it shows gumble user, named "gumble-client" by me cannot transmit or receive any audio, but I have changed the config "opusthreshold=0" in murmur.ini.

Also, when I run mumble-audio-player, it shows that "audio player loaded! (0 files)", and no sound played. Is it normal? I think it should find chimes.ogg in path "../go/src/layeh.com/gumble/_examples/mumble-audio-player", but it not. Is it an error, or chimes.ogg on an incorrect path?

More information or hints about how to debugging gumble for audio is needed.