Final answer:
The intensity needed to detect a change in the number of people talking in a room becomes greater as the number of people talking increases, demonstrating the concept of Weber's Law and the difference threshold.
Step-by-step explanation:
The principles of sensory perception, particularly the Weber's Law, which relates to the difference threshold or just noticeable difference (JND). As the number of people talking in a room increases, the stimulus intensity needed to detect a change in the number of people talking becomes greater.
This means that when the room is already noisy, it requires a significantly larger addition to the sound for someone to notice a change compared to when the room is quiet. To illustrate this, imagine a room with 2 people talking. If a third person starts talking, this change is quite noticeable.
However, if there are 20 people talking, and a 21st person joins in, discerning this change becomes much harder. The intensity of the initial stimulus (i.e., the sound level with 20 people talking) is greater, so the amount of change required to notice a new voice is also greater.