I wouldn't translate שינה ערבה (BTW, no need for the yod between the resh and the vet) as 'to sleep soundly'. The latter is לישון שינה עמוקה in Hebrew. I'd translate as 'I had sweet dreams', or something to that effect, such as 'I slept very well' or 'I had a very good night's sleep'. Of course, context is everything. That being said, if you translate ערבה as 'sound', something is lost, and needlessly, in the translation, and the question arises: Why was ערבה used to start with? Why not עמוקה, which indeed means soundly?