"to kiita" & "sou da" both mean ( I

[xmoonsirenx]

What is the difference between:
1."sou da (I heard that)"
and
2."to kiita (I heard that)"


Questions:
1. Both mean the same thing right?
2. Can they be used interchangeably?

For example, I found this sentence which uses "to kiita", but can I use the "sou da" form as well?

a) We heard that the weather was bad, so we decided to put off our trip.
tenkou ga warui to kiita node ryokou ha enki shi ta .

b) tenkou ga warui kiku sou da...dakara ryokou ha enki shita.
We heard that the weather was bad so we decided to put off our trip.

Please help, thank you.

[jkerianjapanesepod5596]

"to kiita" means literally "My ears heard X". This can be used to refer to something someone said, as well as any other sound.

Whereas "sou da" means something more along the lines of "I'd heard (from somebody) that Y". Perhaps the english equivalent would be "They say that Y" (where "they" is not specified). Generally speaking, the person who said Y is not specified, but might be implicit due to the nature of the conversation.

[Javizy]

'sou da' isn't exactly formal as such, but it can sound kind of stiff in conversation, especially if you cite the source with 'ni yoru to'. You hear it a lot in the news, whereas you'd probably hear 'rashii' in speech. 'sou da' is kind of like reporting information, whereas 'rashii' allows you to more casually talk about something you've read/heard from somewhere you may or may not remember that may include a bit of conjecture/guesswork. You can make 'sou da' a bit more convo friendly if you add on 'yo'.