你把 turn off 的用法想简单了。
查柯林斯英语词典,它对 turn off 的相关解释是这样的:
PHRASAL VERB 短语动词
关上;关掉;截断,切断(…的供应)
When you turn off a piece of equipment or a supply of something, you stop heat, sound, or water being produced by adjusting the controls.
由此可见,你“关掉”的不仅可以是“设备”(a piece of equipment),也可以是“切断(…的供应)”,包括切断 sound的供应。
所以,你的句子完全没有问题!