An Informal way to get another person's awareness, much like a whistle, is really a hissing audio: "pssiu!" It's not at all perceived as impolite, but gets truly irritating if repeated also typically. It is especially commonplace before and during Carnival (Brazilian Mardi Gras), and also occurs throughout the year. https://wiki.brandwoot.com/profile.php?user=gidget-bugden-146601&action=view