Open up your EQclient.ini file (in your installed folder) and make sure sound=true (should be the first thing there). Save it and try again!
[Defaults]
Sound=TRUE
TextureQuality=1
VertexShaders=TRUE
20PixelShaders=TRUE
14PixelShaders=TRUE
1xPixelShaders=TRUE
MultiPassLighting=FALSE
UseLitBatches=TRUE
InspectOthers=TRUE
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