“Waipuna” means gentle spring — but try telling that to those hoping to win a Na Hoku Hanohano Award (aka the Hawaiian Grammy Awards). For the past few years, Waipuna has been more like a mighty wave, wiping out the competition and snagging seven crystal trophies, including those in the “Group of the Year,” “Island Contemporary” and “Single of the Year” categories. The source of their strength? A unique sound that springs from ancestral traditions even as it ventures into new waters. And some damn fine string playing too.