Third-party call centre application is connected to CUCM7.1.5 via a SIP trunk. Call centre agents have nailed-up calls to CUCM - incoming calls are connected by the call centre application to the agents (all 7942 phones). When the agent is not in a customer call, because there is a silent call active to the call centre application, they receive comfort noise which they find irritating. How can I disable comfort noise, either on a per-phone basis or globally? All I can find on this is references to PSTN calls and configuring comfort noise on voice ports; that doesn't apply in this case as no PSTN calls are active when the comfort noise is received.