Both my DD's did it, but DD1 to a much greater extent. My health nurse heard her doing it and said it was due to my forceful letdown and that it was DD's was of dealing with the letdown. It didn't cause her any trouble or annoy her, and didn't cause any wind so I just let her grow out of it My DS who had a very mild tongue tie never made the noise. He dealt with the forceful letdown by coughing and spluttering milk over me hehe