They're used to listen to different things. The diaphragm is in my experience much more important. TBH I never even use the bell. Some pediatricians like it for

They're used to listen to different things. The diaphragm is in my experience much more important. TBH I never even use the bell. Some pediatricians like it for infants because it is physically smaller (but they put a smaller diaphragm over it). Lots of stethoscopes don't even have one. Funny article about the bell: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1790765/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1790765/