Heart Beat or Machine Sound?

Today, my parents bring my to Dr Jason in Sunday Medical (http://www.sunway.com.my/sunmed/main.htm), who will probably help my mum to deliver me...

My silly mummy ask Dr Jason how come there ins't any sound for my heart beat.

Dr Jason replied:"Why? Why you need the sound? The sound is just a machine noise and doen't add any information to you...."

So, my mum very disapoited, she though she can hear my heart beat...