Marvel: Superhuman Vocal Stamina

Sean Cassidy (Banshee)
He possesses superhuman stamina in his lungs, throat, and vocal cords.

Theresa Cassidy (Siryn/Morrigan)
Her vocal cords are tremendously strong so that she can produce sonic effects through screaming constantly for hours at a time without noticeably tiring or injuring her vocal apparatus. Siryn's vocal cords and the interiors of her throat and mouth are also superhumanly tough, so that the intense pressures and constrictions that she produces do not cause her any injury.