Bats are unique among mammals, relying on sound more than sight to perceive their environment during nocturnal activities. The sounds they make are complex, existing across a wide spectrum that stretches far beyond the limits of human hearing. Understanding what a bat sounds like requires recognizing the difference between the noises we can detect and the high-frequency acoustic signals that make up their world. The majority of their vocalizations are inaudible to us, forming a hidden language of navigation and hunting that scientists access with specialized equipment.
Sounds Bats Make That Humans Can Hear
While the primary sounds bats use are ultrasonic, they also produce lower-frequency calls that fall within the average human hearing range (up to about 20 kilohertz, or kHz). These audible sounds are generally social and serve as communication tools within a colony or between individuals, not for navigation or object detection.
In a roost, bats engage in social chatter, including squawks, clicks, and squeaks related to establishing territory or minor squabbles. Mothers and pups use specific, audible calls for recognition and bonding, allowing them to locate each other in a densely packed colony. When captured or threatened, a bat may emit a loud, broad-spectrum distress call. These calls are lower in frequency and higher in volume than other social signals, allowing them to travel farther and alert other bats to danger.
The Inaudible Language of Echolocation
The sounds most characteristic of a bat’s life are their echolocation calls, which are largely inaudible to humans because they consist of ultrasound. Ultrasound refers to sound waves with frequencies above 20 kHz, the upper threshold of human hearing. Bat calls typically range from 9 kHz up to 200 kHz, with most species relying on frequencies between 20 kHz and 120 kHz.
These ultrasonic pulses are brief, lasting only a few thousandths of a second, but they are emitted at high repetition rates. Depending on the species, the sounds can be loud; some “shouting” bats produce calls reaching 110 decibels at the source, comparable to a smoke alarm. The sound dissipates quickly over distance. Since humans cannot naturally perceive these high-frequency signals, researchers use bat detectors to translate the ultrasonic calls into a lower, audible frequency.
Interpreting the Echo: How Bats Use Sound to Navigate
Echolocation is a sophisticated biological sonar system that allows bats to construct a detailed acoustic map of their surroundings in darkness. The bat produces a high-frequency sound pulse through its mouth or nose, then listens for the echo that returns after the sound wave strikes an object. The time delay between the call’s emission and the echo’s reception determines the distance to the object. A quick return indicates a nearby object, while a longer delay means the object is farther away.
The bat’s brain analyzes the intensity (loudness) of the returning echo, which provides information about the target’s size and reflectivity. A strong echo suggests a large or hard surface, while a weaker echo might indicate a small insect or soft foliage. As a bat approaches prey, its pulse rate rapidly increases from a searching rate of about 10 calls per second to a “feeding buzz” of up to 200 calls per second. This rapid-fire pulse rate provides near-continuous updates, allowing the bat to precisely track and intercept a fast-moving insect. Specialized ears and complex brain processing allow the bat to interpret subtle frequency shifts in the echo, known as the Doppler effect, which reveals the target’s speed and direction of movement.