playback wav file

//sound(myjoy.wav) is at
/var/lib/asterisk/sounds/dave_sounds

//extensions.conf
exten=>110,1,GoSub(moh,play,1());

[moh]
exten => play,1,Answer()
        ;same=>n,MusicOnHold(jazz)
        same=>n,Playback(dave_sounds/myjoy)
        same=>n,Hangup()

//stacktrace
--- (11 headers 0 lines) ---
    -- Executing [play@moh:2] Playback("SIP/20-0000000a", "dave_sounds/myjoy") in new stack
[Sep 25 15:44:13] WARNING[23877]: format_wav.c:102 check_header_fmt: Not in mono 2
[Sep 25 15:44:13] WARNING[23877]: file.c:390 fn_wrapper: Unable to open format wav
[Sep 25 15:44:13] WARNING[23877]: file.c:962 ast_streamfile: Unable to open dave_sounds/myjoy (format 0x4 (ulaw)): No such file or directory
[Sep 25 15:44:13] WARNING[23877]: app_playback.c:475 playback_exec: ast_streamfile failed on SIP/20-0000000a for dave_sounds/myjoy
    -- Executing [play@moh:3] Hangup("SIP/20-0000000a", "") in new stack
  == Spawn extension (moh, play, 3) exited non-zero on 'SIP/20-0000000a'