Bats' Vocal Structures for Echolocation and Social Communication Ranges Up to 7 Octaves on Piano Scale

Bats can chase and seize fast-moving airborne prey thanks to the emergence of flapping wings, echolocation, plus subsequent quick buzzing, allowing them to capture the treasures of the night: winged insects. Biosonar signals must have high frequencies to allow efficient acoustic reflections and a large bandwidth to give excellent positioning accuracy and spatial precision for detecting tiny prey.

Echolocation consequently favors greater fundamental frequency and range expansion, and several species of bats (FM bats) emit perfectly timed, frequency-modulated echolocation sounds that sweep in from as high as 125 kHz down to around 10 kHz in calls lasting only 1 to 2 ms.

Following a recent study published in the prominent journal PLOS Biology, bats employ the same approach as human death metal performers and throat-singing Tuva tribes in Siberia and Mongolia for some sounds.

The Flying Death Metal Vocalists of the Night

The study was conducted by a research team led by Professor Coen Elemans of the Department of Biology at the University of Southern Denmark. The researchers videotaped what happens in a bat's larynx as it generates sound for the first time.

For the first time, we discovered which physical parts within the larynx vibrate to produce diverse vocalizations. Bats, for example, can generate low-frequency sounds using their "false vocal folds," like human death metal vocalists, as stated by Elemans.

False vocal folds are so named because they resemble vocal folds but are not employed in regular human speaking or song. Most death metal growlers and throat singers in a few cultures utilize artificial vocal folds like bats. Humans lower the vocal folds, causing them to vibrate only with vocal folds.

This creates the vocal folds heavy, causing them to oscillate at very shorter wavelengths, according to postdoc Jonas Hkansson, the study's first author. When bats fly into or out of a tightly packed roost, they frequently make growling sounds.

Scientists are unsure what a screaming bat is saying when it employs its artificial vocal folds to make low noises in the 1 to 5 kHz range. Some appear hostile, others indicate irritation, and others serve the opposite purpose. They don't know yet, said co-author and biologist Lasse Jakobsen of the University of Southern Denmark.

Axl Rose got nothin' on bats.
Bats have a frequency range, often known as the vocal range, that significantly exceeds that of vertebrates, including humans. Researchers do not yet understand the significance of all of their noises and songs, but they are learning more about how these sounds are created. yslynskahal / Shutterstock.com
(Photo: yslynskahal / Shutterstock.com)
Bats have a frequency range, often known as the vocal range, that significantly exceeds that of vertebrates, including humans. Researchers do not yet understand the significance of their noises and songs, but they are learning more about how these sounds are created.

7th Voice Octave: Surpassing Mariah and Prince

Bats use echolocation to hunt insects in full darkness. To discover and capture insects, they send out extremely brief, high-frequency sounds and seek echoes bounced from nearby objects.

Following Jakobsen's statement, a bat can discern the form, size, and texture of echoing surfaces in milliseconds. The research also explains for the first time how bats can create their extremely high-frequency echolocation sounds. They do it by buzzing very thin vocal membranes, which humans originally had but lost during evolution.

For the first time, we could video these vocal membranes directly. We needed to video at astonishingly high frequencies, reaching up to 250,000 frames each second, to display their vibrations, based on the IFLScience report. Researchers detect changes in the larynx that account for the bat's capacity to generate extremely high-frequency sounds very quickly, allowing them to catch insects while flying, as per Jonas Håkansson.

The study team emphasized that a bat's natural vocal range covers 7 octaves, which is incredible. Since most animals have a frequency of 3-4, while humans have a range of roughly 3, a few human vocalists can attain a range of 4-5. Mariah Carey, Axl Rose, and Prince are well-known instances. According to Coen Elemans, bats exceed this range by utilizing distinct structures in their larynx.

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