It appears that you can not play a sound file if you have ebeeps disabled. Using version 6.21.

Example
/ebeeps off
//splay $qt($sfile($mircdir))

The file will not play.

/ebeeps on
//splay $qt($sfile($mircdir))

The file plays.

I've tried this by entering just the file name by hand (no identifiers), and used separate files for the tests. Same outcome.