Siri only does that when it hears "Siri" and nothing else, so a wait is still required. When I began using Siri it beeped when it began listening for more after

Siri only does that when it hears "Siri" and nothing else, so a wait is still required. When I began using Siri it beeped when it began listening for more after "Hey, Siri", so I knew immediately that I could continue speaking.