Where is a flat percussion note typically heard?

A flat percussion note is typically associated with areas that contain a denser substance than air, which is why it is often heard over the sternum, skeletal muscles, or regions affected by atelectasis (collapse of lung tissue). In these areas, the sound waves do not travel well through dense materials, resulting in a flatter note compared to the more resonant sounds produced over healthy, air-filled lung tissue.

In contrast, large airways (such as the trachea or bronchi) produce a more resonant sound due to the air passing through them. The stomach, being filled with gas, would generate a tympanic note, which is hollow and higher-pitched. Healthy lung tissue, filled with air, would yield a normal resonance noted as a normal or hyper-resonant sound.

Thus, the presence of a flat percussion note is indicative of pathology or dense structures in the area being examined, validating that the correct answer pertains to locations such as the sternum or areas of atelectasis rather than air-filled or gas-containing structures.