What is true regarding a grade 4-intensity murmur?

A grade 4-intensity murmur is characterized by being very loud and is typically associated with a "thrill," which is a palpable vibration felt on the chest wall that corresponds to the murmur. The presence of a thrill indicates significant turbulence in blood flow and suggests that the murmur is not only audible but also strong enough to create enough energy that can be felt externally. This often occurs in cases of severe valve disorders or congenital heart defects, making it an important sign for clinicians to recognize during a cardiovascular examination.

The other choices reflect lower intensity levels or variations in auscultation but do not accurately describe the characteristics of a grade 4 murmur. For instance, while a grade 4 murmur is indeed loud, it goes beyond merely being "moderately loud" as suggested by one of the choices. Additionally, while it's true that some murmurs can be heard with the stethoscope partially off the chest, this is not typical for a grade 4 murmur, which requires good contact for optimal sound transmission. Hence, the association with a thrill is the defining feature of a grade 4 intensity murmur, making this the correct understanding.