A swishing or bruit sound heard over the carotid is an indication of turbulence in the carotid circulation. The turbulence may be caused by arterial stenosis (narrowing). It is not possible to predict the amount of stenosis present. An ultrasound of the carotid will provide that information
when we accelerate vehicle the supply of fuel gets increased .. Then inside the combustion chamber all the charge can't burn in such case so phenomena of knocking takes place.. So the sound can be heared.