/var/lib/asterisk/sounds/en
に
*****.gsm
がたくさんあるので、
/etc/asterisk
の
extensions.conf
に追加

exten => 9003,1,Playback(queue-callswaiting)
exten => 9004,1,Playback(please-try-again)
exten => 9005,1,Playback(queue-holdtime)
exten => 9006,1,Playback(queue-thereare)
exten => 9007,1,Playback(queue-reporthold)
exten => 9008,1,Playback(queue-periodic-announce)
exten => 9009,1,Playback(invalid)

以上