Answer: Susan's detection of the increase and decrease of volume is an example of: DIFFERENCE THRESHOLD ALSO KNOWN AS NOTICEABLE DIFFERENCE.
Step-by-step explanation:
The just noticeable difference (JND), also known as the difference threshold is the change in stimulation that we are able to detect half of the time.
There is an absolute threshold which can be confused with difference threshold. Absolute threshold means we can detect smallest levels of stimulation like detecting the lowest volume of sound. Difference threshold means we can detect differences in level of stimulation like sensing the volume change in the radio.
For Susan to detect the difference between volume of 14 to 15 is a result of difference threshold.