Final answer:
The correct answer to the question is voice-pitch analysis. It is a method that assesses the emotional intensity by measuring the frequency of a subject's voice, distinguishing it from intensity, which is measured in decibels. Pitch is unaffected by volume changes, and frequency observations can vary based on the relative motion between the source and observer.
Step-by-step explanation:
The device used to assess the emotional intensity in a subject's responses by measuring the relative vibration frequency of the subject's oral response is voice-pitch analysis. This technique analyzes variations in the pitch of the voice, which can fluctuate with psychological arousal. It is important to note that pitch and intensity are distinct properties of sound; pitch corresponds to the frequency of the sound waves, while intensity is related to the amplitude of the waves and is commonly measured in decibels. The pitch does not change if the volume (intensity) is increased or decreased, as illustrated by GRASP CHECK, which highlights that increasing the volume on a stereo does not alter the pitch because pitch does not depend on intensity. Additionally, the observed frequency of a wave, including sound waves, can be affected by the relative motion of the source and the observer, qualifying as a qualitative measurement.