How to set up QoS for Voip on a 5224

Hi chaps,

I dont know if it's possible but I'm guessing something may be, but we have a PC 5224 switch here which has been doing a great job on our small office network. 

We have VOIP phones here and for 18 months we haven't had an issue but now that we have more users in the building (from 4 to about 12) we are finding the odd audio issue and want to rule out any QoS (or total lack of it in our case) as an issue.

Are there any guides on doing basic QoS for Voip with the 5224's? 

We have a 3CX phone server here, running on an old box in the corner and a mix of Grandstream and Snom phones. 

The phones connect to the 3CX server over port 5060. There's no Vlan here in place, no switch management of any kind really, though we have dived in to the switch web interface on occassion.

In basic, we're total noobs :)

Any suggestions?

Olly