In the attached simple test code, QAudioDeviceInfo::availableDevices fails to reflect any changes in the available audio devices (caused by un/plugging USB audio devices while running). New devices plugged in are not reported while unplugging a reported device causes the error "QAudioDeviceInfo: Unable to find device name" - presumably because QAudioDeviceInfo tries to reference the device that no longer exists.

The problem disappears when the QCoreApplication is replaced with a QApplication; it seems that QCoreApplication does not forward the relevant signals from the audio backend while QApplication does.