Minecart sound stops permanently

I have an auto pumpkin farm using pistons and a minecart hopper. But when the pistons activate the sound of the minecart moving stops and i have to leave the area before the 'wooshing' sound of the minecart comes back.

I know this doesn't seem like a big issue - who likes hearing the relentless roar of a perpetually moving minecart? - But because I couldn't hear it going, i assumed - multiple times - it had stopped and so constantly dug up the ground works to try and rectify a problem that didn't exist.

 

Thank you.