What type of sound is primarily caused by facility users?

The correct answer is air-borne sounds. These sounds are primarily produced by facility users through activities such as talking, cheering, or using equipment like microphones or speakers. In sports facilities, the audience's reactions, athletes' communications, and other verbal or audio interactions create sound that travels through the air.

Air-borne sounds are especially significant in venues like stadiums or arenas, where a considerable amount of noise can emanate from large crowds and events, impacting both the experience of attendees and the facility's overall sound management.

In contrast, structure-borne sounds refer to vibrations that travel through the building's structure, which might be generated by machinery or impacts rather than the users themselves. Electrical sounds involve noise from electrical systems and appliances, while operational sounds pertain to noises from equipment and facilities' operation, which typically would not be directly caused by users in the same way as air-borne sounds.