So in my story, the "antagonists", I guess you could call them, are 8-9 foot humanoid lizard aliens (yeah fun right?). They are delighted at the sight of the protagonist and make a noise. I'm not an expert in lizards and I was wondering what kinds of sounds lizards make during certain situations. Through a little bit of online digging, I've found out that they trill, squeak, and hiss, but I haven't been able to find any good videos of them making noises. Also, does anyone have any onomatopoeia words for the trill?