騒音

The term refers specifically to sounds that are perceived as unpleasant, disruptive, or harmful. Unlike the neutral word "oto" (sound), "souon" always carries a negative connotation. It is often used in formal, technical, or legal contexts, such as environmental regulations or apartment rules.

In daily conversation, while "souon" describes the phenomenon of noise, the adjective "urusai" (noisy/loud) is more commonly used to express the immediate feeling of being annoyed. For example, you would say "Urusai!" to someone making noise, but you would use "souon" when discussing the problem of noise pollution in a report or a formal complaint.

It is frequently paired with terms related to mitigation or regulation, such as "souon-boushi" (noise prevention) or "souon-kōgai" (noise pollution), highlighting its status as a nuisance to be managed.