In "Biblical Perspective" Gordon Snider writes concerning Psalm 19:3:
There is no speech nor language, no place on earth, that can block out the music of nature. Another possible interpretation is that the heavens do not need human speech to say what they wish to declare. We often talk about natural revelation, and we base that revelation in part upon this verse. But it is questionable whether the intent of nature's song is to inform about God so much as it is to glorify Him (Ps. 148:1).
Source: Studies in the Psalms: Adult Teacher's Insights, page 11.