Impedance changes with bounding surface area and cause reflections in instruments.

Evidence

This means that for bounded waves the impedance depends on the surface area within the bounding structure and so will change as the area changes. As we shall see later, changes in impedance can cause reflections. This effect is important in the design and function of many musical instruments as discussed in Chapter 4. — David Howard, Jamie Angus, coustics and Psychoacoustics, 159

Categorization

• XREF: Establishes impedance-mismatch cause of reflections, the same principle used in acoustic impedance matching for mufflers and stethoscopes.