If your worst nightmare had a soundtrack, the Aztec death whistle would be prominently featured. In the hands of a skilled user, the instrument creates the spine-tingling wail of a thousand tortured souls being carried on a cold wind–with the screams and death rattles of a few wild jungle animals mixed in.

Listen at your own risk, however; once heard, this unnerving sound cannot be forgotten. Scientists are still piecing together the story of these ancient Mesoamerican creations, which usually are made in the shape of human skulls or animal heads–mouths open and teeth bared.

One was found beneath Mexico City in 1999, clutched in the skeletal fingers of a sacrifice victim in the ruins of a 650-year-old temple of the wind god. The location suggested to some that the whistles were intended to evoke the sound of the howling wind.