Communication Panel remains active even when there's no active call. Agent can also hear background noise when there's no call.
The functionality works as designed. By keeping the audio channel open for Communication Panel the connection between client and backend is also kept active.
However, you can change this with the configuration parameter keepAudioDeviceActive in CommunicationPanel.json file. The file is located under ECF_Agent\tomcat\webapps\ECFSettings and has the following content:
Change the value true to false, which means that the audio channel is no longer active.
Sinch Contact Pro never listens to agents via an audio device when there's no call. And the only situation when agents' calls are saved is when the admin has configured call recording in System Configurator.
Before you change the functionality consider that the change can cause side effects, such as agents not able to answer calls and queuing calls not allocated although agents are free.
If you decide to change the functionality: