Bats use the same trick as death metal growlers and throat singers

MARY LOUISE KELLY, HOST:

If you've ever sung karaoke, you're aware that the vocal range of most humans is pretty limited - three octaves maybe, maybe four or five if you're really good, like Mariah Carey.

(SOUNDBITE OF SONG, "EMOTIONS")

MARIAH CAREY: (Singing) You make me feel so high.

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ARI SHAPIRO, HOST:

But even Mariah Carey wouldn't stand a chance against a bat. They can pull off seven octaves.

COEN ELEMANS: So basically, we were interested in, like, how can bats make all these different sounds? Well, they sort of make low-frequency calls and make echolocation calls, and they span together, like, seven octaves.

SHAPIRO: Coen Elemans is with the University of Southern Denmark. He and his colleagues used ultra high-speed video, filming up to a quarter million frames a second, to study what's going on in bats' vocal tracts.

ELEMANS: We basically found that bats make echolocation calls using very thin membranes, so they basically are extending from the vocal folds.

KELLY: The idea was to study how bats make the super-high-pitched echolocation calls that they use to find prey. But when the scientists looked at the other end of the register, at the low calls that bats make, they found something surprising. They discovered that bats seemed to recruit a different part of their vocal tract, which they say is analogous to how humans pull this off...

(SOUNDBITE OF SONG, "SLOWLY WE ROT")

OBITUARY: (Singing) Fight them all in a living hell. Slowly rot, and you die.

KELLY: ...Or this.

(SOUNDBITE OF SONG, "SHAMAN")

HAYK ROMIA: (Singing in non-English language).

ELEMANS: So like death metal singing or deep throat singing. In humans, these folds have been called the false vocal folds because they have no function in normal speech, so they don't seem to do anything - only in the sort of some extreme forms of singing.

SHAPIRO: Now, to be clear, the low sounds the bats make do not sound like death metal or throat singing. Here's a sample.

(SOUNDBITE OF BAT CLICKING)

SHAPIRO: Remember; this is low for a bat, so it still sounds high and squeaky for us. Slowed down 50 times to hear it better with human ears, it sounds kind of sinister.

(SOUNDBITE OF BAT CLICKING)

KELLY: Wow. The scientific findings appeared this week in the journal PLOS Biology. And while we could not ask the bats what it is like making those low-register sounds, we could ask some human practitioners of the death metal growl.

(SOUNDBITE OF SONG, "SLOWLY WE ROT")

OBITUARY: (Singing) Dead to all, fighting as you're slowly...

JOHN TARDY: I mean, it's from your abdomen to your chest to your legs to obviously a lot of your throat. But it is a full-body thing for me in order to do what I do.

SHAPIRO: John Tardy is lead singer of the death metal band Obituary, heard there on the track "Slowly We Rot." He called us from the back of his bus in Pittsburgh. And he says your voice can really take a beating on tour.

TARDY: It can be, you know, strenuous because we do - you know, we usually play most nights, if not six nights a week. So it can be a lot. But I can tell you at the end of every night, I sleep like an absolute baby (laughter).

KELLY: Chase Mason of the group Gatecreeper says pain is just part of the process for him.

CHASE MASON: In a sadistic sort of way or masochistic - I don't know what the correct word would be. But I think that, when I can feel that my vocal cords are getting kind of shredded or beat up, that it sounds better. You know, like, if there's a little taste of blood in the back of my throat, I think that I'm doing a good job.

KELLY: Oh, my God. His advice for listeners who want to try the death metal growl...

MASON: I would tell them to go into their closet and just, like, try to yell as loud as they can just so you can get used to how it feels. I think that a big part is getting over the initial shock of just doing something pretty extreme with your body.

SHAPIRO: I'm going to leave that to the bats.

(SOUNDBITE OF SONG, "FROM THE ASHES")

GATECREEPER: (Singing) Wandering through chaos, scarred from nightmares, broken down, haunting aglow - liberated, accelerating forward. Transcript provided by NPR, Copyright NPR.