Final answer:
The distracting hum of a light fixture is background noise, which refers to any unwanted and distracting sound that is present in a given environment.
Step-by-step explanation:
The distracting hum of a light fixture is background noise. Background noise refers to any unwanted and distracting sound that is present in a given environment. In this case, the hum of the light fixture can be considered background noise because it is a continual and persistent sound that can interfere with concentration and focus.