Final answer:
The hum of a light fixture is categorized as physical noise, which is an external sound that can disrupt communication or concentration.
Step-by-step explanation:
The distracting hum of a light fixture is considered physical noise. Physical noise refers to any external, tangible sounds that interfere with the process of communication or a person's concentration. This type of noise is an actual sound wave that reaches the ears and can detract from the intended audio or disrupt quiet concentration environments. Other types of noise, such as psychological (related to personal thoughts or emotions), chronological (related to time), or physiological (stemming from within one's own body), do not apply in this context.