Why do i hear a whooshing sound when i change position (such as lying on my stomach, or standing after sitting or lying)?

Succussion splash?: Consider gastroparesis=a slow-emptying stomach that is most symptomatic after the stomach fills from meals. Maybe its functional due to brainstem reflexes induced by eating--often exaggerated in irritable bowel syndrome resulting in altered perception of gut distension, "growling", &modified transit of food. Sometimes, gastric outlet delay may reflect inflammation, scarring, biliary disease, more.