umblicus
Your heart beat of course.
The valves opening and closing
Apex
Audible sound is the sound which is between 20 Hertz to 20000 Hertz and can be heard by human beings, whereas Inaudible sound may be below 20 Hertz or above 20000 Hertz and this can't be heard by human beings.
systolic
The function of the tubing in a stethoscope is to magnify the sound waves by making them narrow enough to be heard at an accurate timing through the ear canal.
The human range of hearing is from 20 Hertz to 15,000 Hertz, with individual variations. Most humans lose some of their higher range as they age.
The sounds of the Heart, lungs, circulatory and gastrointestinal systems are heard using the amplified stethoscope. It makes it easier for a medical professional to hear the sounds that are produced by these systems in the body.
I work for Enterprise and I certainly haven't heard that rumor. If Hertz were going out of business, I would expect it to be the talk of the industry.
The woman's pulse is found the usual way at the neck or on the wrist. The baby's pulse can be heard with a stethoscope.
When the doctor listens to the lungs through a stethoscope (ausculation), diminished or bronchial breath sounds may be heard. By tapping on the chest (percussion) while listening through the stethoscope, the doctor can often tell if the lung is collapsed