そう "seem" used for hearing

Question

In a book someone hears a woman voice and says:

心配そうな、お母さんの声

As far as I know, そう(な) is to say something seems based on visual information, and my grammars agree with this: things like おいしそうなケーキ. If linked to something you heard, そう is used to report what you said/heard, like 明日だそうだった, "I heard it's tomorrow".

Given the context, it seems to me that そう is the first meaning, since the character isn't reporting something she heard.

Is that そう the first meaning? If so, is that use wrong/unusual?

Answer 1

When you use そう, your judgement can be based on any of your five senses:

• [after seeing a dish] おいしそう。
• [after hearing about a dish over a phone] おいしそう。
• [after lifting a box up] 中に何か入ってそう。
• [after smelling a dish] 腐ってそう。
• [after tasting a dish] ワサビが入ってそう。

そう for hearsay has nothing to do with this because it must follow a dictionary form of a verb/adjective. "I heard [he] is worried" is 心配だそうだ.