What would someone hear or not hear with a stethoscope when listening to their stomach/bowels if their very constipated?

Bowel sounds: The interpretation of bowel sounds from normal to findings of abnormal takes years to master beyond verbal description. No disrespect it's a doctor thing if having difficulty should seek medical attention not depend on description. To much left to interpretation. Findings could be normal to high pitched to absent all have interpretation with circumstances.

Interesting question: Constipation has many causes but a common one is lack of peristalsis, the wave like motion that passes the contents down for final elimination.Normal peristalsis causes a few fluid-like noises called borborygmi by doctors. Thus you might hear less of those noises than usual. The trouble is that it is a judgment call made by doctors and takes experience.