Which of the following are causes of ECHO? (Choose two.)

Headsets can cause echo when audio leaking from the earpiece is picked up by the closely positioned microphone, creating an acoustic feedback loop that sends the far-end audio back as echo. This is especially common with poorly shielded or improperly fitted headsets where speaker-to-mic isolation is inadequate.

Speakerphones are a primary cause of echo because the room-facing speaker projects audio at sufficient volume for the device's microphone to capture it and retransmit it back to the far end. The physical separation and open-air acoustic path between speaker and microphone makes coupling much more pronounced than in a standard handset.

Radio interference introduces noise, static, or packet loss into a call but does not create the delayed acoustic feedback loop that defines echo.

High volume can amplify or worsen existing echo but is not itself a root cause; echo originates from acoustic coupling in the device hardware, not from the volume level setting.