expression, suru verb (irregular)
raise one's voice; emphasize; speak loudly about
Used when someone speaks more loudly or emphatically to stress a point, often in the context of asserting an opinion or making a declaration.
彼は反対意見を声を大にして主張した。
He raised his voice to assert his opposing opinion.
安全の重要性を声を大にして訴えたい。
I want to speak out loudly about the importance of safety.