If a man speaks there slowly in a deep voice, the low-frequency components of his speech will be considerably amplified and a deep, ringing sound will fill not only the oracle chamber itself, but also the circumjacent rooms with an awe-inspiring sound. (A child or a woman will not be able to produce this effect, the fundamental pitch of their voices being too high to activate the resonator.)

Schafer, Murray R, The Soundscape- Our Sonic E…, loc. 715