Heartbeat sound @ 17 weeks

Hello po, just wondering. 2nd check plang po ng heartbeat ni baby thru portable doppler, heartbeat is within normal range kaso mejo pasweet yung sound compare nung first time na parang drum beats kalakas. Does the sound really change or it doesn't matter as long as baby got a good cardiac activity? I'm a bit worried po kase. TYIA for the feedbacks ❤️❤️