After a call is answered, CallHub listens for 5 seconds to determine if a human or an answering machine has picked up. If an answering machine is detected, then it waits for 2 seconds of silence. 2 seconds is silence, indicating that the initial greeting in the answering machine is complete and the machine is waiting for the messages. CallHub will then play the audio file into the answering machine.
Answering machine detection is not accurate 100% of the time. It is accurate at about 60-70%. The failure rates are higher on landlines with answering machines with an initial greeting message less than 5 seconds long.
Although the failure rates are almost the same across all the platforms, the failure rates are higher for cell phones because the telecom carrier handles the voicemail on a cell phone.
Voice broadcasting is better suited for calls optimized for contacts answering the call.