喧哗 (xuānhuá) is a formal, written word for 'noisy, clamorous' — it often describes a loud, disruptive crowd or public noise (e.g., in libraries, public spaces). It's more literary than 吵 (chǎo) or 闹 (nào), which are everyday spoken words for 'noisy' or 'making a racket'. 喧哗 is rarely used as a verb in speech; its verb sense ('to clamor') is very formal.