Most of what a bat sounds like in flight is silence, at least to human ears. The majority of bat species echolocate at ultrasonic frequencies well above the roughly 20 kHz ceiling of human hearing, so a bat swooping past your head on a summer evening is doing something acoustically extraordinary that you simply cannot perceive. But bats are far from soundless. Some species call at frequencies low enough for people to hear as rapid, sharp clicks or chirps. Wings generate their own faint aerodynamic noises. And when bats hunt, socialize, or navigate crowded spaces, the acoustic picture gets remarkably complex, involving everything from screaming-loud sonar pulses to delicate wing-produced clicks.
The Echolocation Soundtrack You Mostly Cannot Hear
Echolocation is the dominant sound a bat makes while flying. A bat emits pulses of sound, listens for the returning echoes, and builds a real-time acoustic map of its surroundings. Most insectivorous bats echolocate in the range of about 20 kHz to well over 100 kHz. Because human hearing tops out around 20 kHz, the vast majority of these calls are completely inaudible to us without a bat detector, a device that shifts ultrasonic frequencies down into the range we can hear.
A handful of species break this rule. The spotted bat, for instance, produces echolocation calls that are lower in frequency, shorter, and fainter than those of most other insect-eating bats, making them relatively easy for a person standing nearby to pick up as a faint, high-pitched ticking.
At the other end of the spectrum, some open-air hunters are extraordinarily loud. Bats that chase insects in open spaces have been recorded producing echolocation calls above 135 dB SPL, which is roughly comparable to the sound level of a jet engine at close range.1PubMed Central. Intensity and directionality of bat echolocation signals You would never know it, because the energy is concentrated at frequencies you cannot hear. If your ears could detect 40 kHz, a noctule bat passing overhead would be deafening.
How Frequency Shapes What You Might Hear
The frequency a bat uses is not arbitrary. It reflects where and how the bat lives. Species that hunt in open habitats tend to use lower frequencies, which travel farther through air before fading out. Species that forage in dense vegetation or cluttered environments use higher, broader-bandwidth calls that give finer spatial detail but fade rapidly. Call features like frequency, bandwidth, duration, and pulse interval are all tied to a bat’s ecological niche, and environment often matters more than evolutionary relatedness in shaping call design.2PubMed Central. Bat echolocation calls: adaptation and convergent evolution
The atmosphere itself acts as a low-pass filter for ultrasound. Higher frequencies experience dramatically more severe attenuation. Bats calling above 100 kHz face attenuation rates exceeding 3 dB per meter, which means the useful range of their sonar shrinks to just a few meters.3PubMed. Measurements of atmospheric attenuation at ultrasonic frequencies and the significance for echolocation by bats For a person trying to hear bats, this means the lower-frequency species, calling around 20 to 25 kHz, are the ones most likely to register as faint, rhythmic clicking if you have sharp hearing and stand close enough.
Weather also plays a role. Temperature and humidity alter how quickly sound fades and how fast it travels through air. A bat calling at 80 kHz in warm, dry conditions faces roughly six times more atmospheric attenuation than one calling at 20 kHz, and the gap shifts noticeably with weather changes. Researchers have documented that a drop in temperature and rise in humidity reduced attenuation for high-frequency callers by about 1 dB per meter over the course of a season, while low-frequency callers barely noticed the difference.4PubMed Central. Weather conditions determine attenuation and speed of sound: Environmental limitations for monitoring and analyzing bat echolocation The practical upshot: on a cool, humid night, ultrasonic calls carry a bit farther and bat detectors pick up activity at greater distances.
The Feeding Buzz
If you could hear the full ultrasonic range, one of the most dramatic moments in a bat’s flight would be the feeding buzz. When a bat closes in on an insect, it switches from relatively slow, spaced-out search calls to an extraordinarily rapid burst of pulses. During this buzz, bats ramp up their call rate to as high as roughly 220 pulses per second, flooding their sonar system with information about the target’s position as it changes moment to moment.5PubMed Central. How the bat got its buzz The pulse rate during the final buzz can exceed 180 Hz, and the entire sequence lasts only a fraction of a second.6PubMed Central. Fast sensory-motor reactions in echolocating bats to sudden changes during the final buzz and prey intercept
Even with a bat detector, the feeding buzz sounds less like individual clicks and more like a rapid whirr or zipper being pulled. It is functionally the bat switching from scanning mode to lock-on mode. If you are standing near a pond where bats are scooping up insects, a detector will pick up these buzzes as sudden accelerations of sound followed by brief silence as the bat processes its catch.
Wing Sounds and Aerodynamic Noise
Echolocation gets the attention, but bat wings themselves produce sound. All flying animals generate aerodynamic noise simply by moving air, and researchers have identified at least eight distinct mechanisms by which wings can create sound. Five of these are aerodynamic, produced by airflow, and three are structural, produced by solid surfaces interacting. Surprisingly, documented examples of bat wing sounds are few. It remains an open question whether bats are genuinely quieter fliers than birds or whether their wing acoustics have simply been understudied.7Oxford Academic. Ways that Animal Wings Produce Sound
The sounds that wings produce in ordinary flight, including low-frequency “whooshes” and faint rubbing noises, form what researchers call the acoustic substrate of flight. For most bat species, these sounds are soft and low-frequency enough that a person nearby might hear a gentle flutter or a faint leathery rustle as a bat passes close overhead. If you have ever stood near a roost exit at dusk and heard a soft whooshing as dozens of bats launched themselves into the air, those were wing sounds rather than echolocation.
Fruit Bats That Click With Their Wings
One of the more surprising discoveries in recent bat acoustics involves Old World fruit bats. Most fruit bats were long thought to lack echolocation entirely, with the Egyptian fruit bat being the notable exception because it echolocates using rapid tongue clicks. But researchers found that at least two other species of nonecholocating fruit bats produce click-like sounds to detect and discriminate objects in complete darkness, and they generate these clicks not with their mouths but with their wings.8PubMed. Nonecholocating fruit bats produce biosonar clicks with their wings
The evidence for wing-based clicking is strong. High-speed video showed these bats kept their mouths shut during sound production, unlike orally echolocating species that fly with their mouths open. The clicks were perfectly synchronized with the wingbeat. When researchers sealed the bats’ mouths, clicking continued. And when they added weight to one wing’s leading edge to make the wingbeat asymmetric, clicking stopped entirely.9Current Biology. Wing-directed clicks in a fruit bat facilitate echolocation The researchers suggested that all Old World fruit bats may be capable of producing these wing clicks. The resulting echolocation is crude compared to laryngeal sonar and does not allow accurate distance estimation, but it works well enough to help bats navigate in darkness.
The Egyptian fruit bat, by contrast, uses its tongue to produce hyper-short clicks and can steer the sonar beam’s direction by moving its tongue. Remarkably, newborn pups already produce these tongue clicks and can direct the beam left and right on the day they are born, following the same alternating pattern that adults use in flight.10PubMed Central. Hearing, echolocation, and beam steering from day 0 in tongue-clicking bats These tongue clicks are audible to the human ear as rapid, sharp snapping sounds and are among the bat echolocation signals people are most likely to hear without equipment.
Social Calls During Flight
Bats are not just echolocating when they fly. They are also talking to each other. Many species produce social calls during flight that serve functions ranging from maintaining group contact to signaling aggression to guiding roostmates home. These calls are often in a different frequency range from echolocation pulses, sometimes lower and more within human hearing range.
Big brown bats, a common species across North America, produce social calls while flying that appear linked to proximity. Researchers found that these bats flew closer together around the time certain social calls were emitted, suggesting that communicative calls are selectively produced when other bats fly near.11PubMed Central. Social calls of flying big brown bats (Eptesicus fuscus) If you hear chattering or squabbling sounds from a group of bats in flight, you are likely hearing social vocalizations rather than echolocation.
Some species use social calls specifically to find their way home. A leaf-roosting bat studied in the Neotropics emitted inquiry calls immediately upon being released in flight, which triggered response calls from roosting individuals within about 178 milliseconds. Bats that received a response almost always entered the roost, while those that got no answer often flew past.12PubMed Central. Social calls used by a leaf-roosting bat to signal location This call-and-response system turns roost entry into an acoustic negotiation audible to anyone standing near the roost.
Adjusting the Signal on the Fly
A bat in flight does not simply repeat the same call over and over. It continuously modifies its echolocation based on what it is doing and what acoustic environment it finds itself in. One of the most striking examples involves horseshoe bats, which use a specialized constant-frequency call. When a horseshoe bat flies toward an object, the returning echo is Doppler-shifted to a higher frequency, just as an ambulance siren sounds higher-pitched when it approaches. These bats compensate for this shift by actively lowering the frequency of their outgoing calls, keeping the echo frequency locked onto a narrow, highly sensitive range in their inner ear.13PubMed. Doppler-shift compensation behavior in horseshoe bats revisited: auditory feedback controls both a decrease and an increase in call frequency The bat effectively tunes its own voice in real time so that the echoes always arrive at the frequency its brain is best equipped to analyze.14PubMed. Binaural influences on Doppler shift compensation of the horseshoe bat Rhinolophus rouxi
Bats also adjust when other bats are nearby and their signals might overlap. In crowded airspace, echolocation calls from multiple individuals can create acoustic interference, making it harder for any single bat to interpret its own echoes. At least some species respond with a jamming avoidance response, shifting the dominant frequencies of their calls to increase the spectral distance between their signals and those of their neighbors.15PubMed Central. Dynamics of jamming avoidance in echolocating bats The stronger the spectral overlap, the bigger the frequency shift. Not all species do this equally well. Researchers found clear jamming avoidance in the European free-tailed bat but not in the Egyptian tomb bat when both were flown with conspecifics, suggesting that this ability varies across species.16PubMed Central. The jamming avoidance response in echolocating bats
For someone standing near a colony exit or watching bats forage in a group, these adjustments mean the soundscape is never static. Each bat is tweaking its frequency, timing, and intensity in response to its own flight speed, the proximity of obstacles, the behavior of prey, and the calls of every other bat in the area. Through a bat detector, a group of foraging bats sounds like a chaotic, overlapping chorus of chirps and clicks, each subtly different in pitch and rhythm.
What a Roost Exit Sounds Like
One of the most acoustically dramatic moments in the bat world is the evening emergence from a large roost. Thousands of bats pouring out of a cave or building in quick succession creates a layered sound that even unaided human ears can pick up. You hear the whooshing of wings, occasional audible social chatter, and sometimes faint echolocation clicks from species that call near the edge of human hearing. Through a bat detector, emergence is cacophonous. Each bat echolocates independently, and the overlapping signals create a dense wall of sound that researchers have to disentangle using specialized software.
Bats navigating these crowded exits face serious sensory challenges. They must sort their own returning echoes from the calls of hundreds of neighbors, reflections off cave walls, and the ambient noise of the colony. The acoustic clutter during emergence is one reason bats have evolved such flexible call strategies, adjusting call rate, intensity, and frequency depending on the density of their surroundings.17PubMed Central. Probing the natural scene by echolocation in bats
Moths That Can Hear Bats Coming
The sounds bats make during flight have not gone unnoticed by their prey. Over 14 families of moths have evolved ears specifically tuned to detect ultrasonic echolocation calls.18Physiological Entomology. Bats and moths: what is there left to learn? When a moth hears an approaching bat, it responds with evasive maneuvers: diving, looping, or dropping to the ground. Some moth species go further and produce their own ultrasonic clicks, which may jam the bat’s sonar or advertise that the moth is toxic.
This arms race has pushed bat sound design in interesting directions. The spotted bat’s unusually low, faint calls may have evolved in part because they are harder for eared moths to detect, making the bat a stealthier hunter.19PubMed Central. The echolocation calls of the spotted bat Euderma maculatum are relatively inaudible to moths Other bats call at frequencies above the hearing range of most moths, or use brief, faint whispers as they close in. The sounds a bat makes are shaped not just by what the bat needs to hear, but by what it cannot afford to let its prey hear.
Did Echolocation Come Before Flight or After?
Whether bats evolved echolocation before, after, or alongside the ability to fly has been debated for decades. The question matters because it shapes how we think about the origins of everything bats sound like in the air today. Molecular evidence complicates the traditional story. A large-scale genetic analysis found that certain microbat families thought to be closely related were actually more closely allied with the megabats (fruit bats) than with other microbats. This implies that laryngeal echolocation either evolved independently at least twice or was lost in the megabat lineage.20Nature. Molecular evidence regarding the origin of echolocation and flight in bats
If echolocation evolved more than once, it means different bat lineages arrived at ultrasonic sonar through separate evolutionary paths, which helps explain why echolocation calls vary so dramatically across species. Horseshoe bats, free-tailed bats, and vesper bats do not sound alike because they are not working from the same evolutionary blueprint. And the fruit bats that click with their wings represent yet another independent innovation, a crude but functional echolocation system that arose in a group that lost or never had laryngeal sonar. The sounds bats produce in flight, in other words, are not one invention used many ways. They are multiple inventions converging on the same problem of navigating in the dark.
Hearing Bats in Practice
If you want to actually hear bats flying, your success depends on species, proximity, and equipment. Standing near a roost exit at dusk, you can often hear wing flutter and faint social chatter without any technology. With a heterodyne or frequency-division bat detector, available for relatively modest prices, even the ultrasonic world opens up. Each species has a characteristic call pattern: pipistrelles produce rapid series of descending chirps, noctules emit alternating high-low calls, and horseshoe bats have their distinctive constant-frequency tone. Experienced bat surveyors can identify species by ear using a detector, much the way birders identify birds by song.
Smartphone apps now exist that use the phone’s microphone to pick up some bat calls at the lower end of the ultrasonic range, though their sensitivity is limited compared to dedicated equipment. For casual listening, the best approach is to find a known flyway or roost, arrive around sunset, stand still, and pay attention. The first sounds you notice are usually wing beats and the occasional high-pitched squeak. The real acoustic drama is happening just above the threshold of what your ears can catch.