My son has justed asked me this little gem; and I can't think why the correct answer is correct.

Q - When travelling at or above the speed of sound you shouldn't be able to hear an object approaching. If that's the case, can you here a Concorde engine if sat towards the front?

A - lots of errs

In theory you shouldn't be able to hear them but I guess because they are structually connected and vibrations can travel 'forwards' is, I presume, part of the correct answer but if anybody can give a more scientific reasoning I'd appreciate it. I will, shamefully, take full credit with my son. Sorry.

Thank you,

Lee