What must be done when using the megaphone during preflight checks?

When using the megaphone during preflight checks, it is crucial to press the "push to talk" button and listen for an audible pop. This action confirms that the megaphone is functioning properly and that it can transmit sound effectively. The audible signal indicates that the device is active, confirming that the functionality is intact before it's needed during the flight.

This step is essential because it ensures clear communication can be established, which is vital for safety in emergency situations or during team briefings. Checking the other items like battery status, visual indicators, or volume settings may also be important operational checks, but the primary focus during this specific check is to confirm that the megaphone is operational with the audible feedback mechanism.