Some headpieces also employ noise reduction technology to eliminate sounds not coming from the earpieces of the stethoscope. how might such technology work?

Noise cancelling headphones have a microphone which listens to the ambient noise. The headphone then processes the sound and provides a wave to produce destructive interference. This cancels the ambient noise.

Explanation:

First, let us understand what interference is. Interference is the phenomenon that occurs when two waves superpose to form a wave which has a different wavelength, frequency, amplitude than the original two waves. When the crest of one wave superposes with the other waves crest then this results in the amplitude increasing. This is known as constructive interference. When the crest of one wave superposes with the other waves trough then this results in the amplitude decreasing. This known as destructive interference.

Noise cancelling headphones have a microphone which listens to the ambient noise. The headphone then processes the sound and provides a wave to produce destructive interference. This cancels the ambient noise.

Explanation:

The Average Distance Of Separation, Measured Between Their Centers, Is 3.07 ✕ 109 Km. (a) Locate The Center Of Mass (in M) Of The Saturn-Neptune System ...