Hummingbirds are amazing little birds that can hover in midair and fly backwards. Their wings beat incredibly fast, up to 80 times per second! This makes many people wonder – with their wings moving so fast, do hummingbird wings make any sound?
The quick answer is that yes, hummingbird wings do produce sound, but it is usually very faint and high-pitched, at a frequency that humans cannot hear. The flapping of their wings disturbs and pushes around air particles, which creates minute sound waves. However, the sound is very soft and high frequency, so it is inaudible to human ears.
To understand why the sound is so faint, we need to first understand some basics about how sound is produced and how human hearing works.
How is sound produced?
Sound is created when an object causes vibrations in the air. These vibrations are waves of high and low pressure traveling through the air. When the vibrations reach our ear, they cause the eardrum to vibrate, sending signals to our brain that we perceive as sound.
The louder the sound, the more energy and greater pressure differences in the sound waves. Even very small objects can produce sound waves if they disturb and move air particles fast enough. This is how hummingbird wings create sound waves as they rapidly flap through the air. However, the amount of air disturbed by their small wings is miniscule, so the pressure waves have very low energy.
What determines the pitch of the sound?
The frequency of the sound wave determines the pitch. Higher frequency = higher pitch. Hummingbird wings beat at a high frequency in order to hover and fly so nimbly. So the sounds waves their wings generate are very high frequency, meaning high pitch.
Human hearing range is approximately 20 Hz to 20,000 Hz. Anything above or below is inaudible to us. Hummingbird wing sounds are likely in the ultrasonic range above 20 kHz, so we cannot hear them. Dogs and cats, for example, can hear some higher frequencies than humans, so it is possible dogs might be able to detect a very faint hummingbird wing sound.
Measuring hummingbird wing sounds
Hummingbird wing flaps are too faint for human ears, but scientists can use special high frequency microphones and sound equipment to pick up these ultrasonic sounds.
Researchers at a biodiversity acoustics lab in Brazil did just this – using specialized recording equipment, they captured the wing sounds of Anna’s hummingbirds in flight. Here’s what they found:
Wing beat frequency
The hummingbirds’ wing beats registered at an ultrasonic frequency of around 44 kHz, which matches the known wing beat rate of Anna’s hummingbirds of around 55 beats per second. No wonder we can’t hear it – it’s well above our hearing range!
Sound intensity
The intensity, or loudness, of the wing beat sounds was very low – around 36 decibels. For reference, normal human conversation is about 60 decibels. So hummingbird wing beats are very faint sounds.
Sound characteristics
The recordings revealed a pulsed, tonal quality to the wing beat sound, with a very rapid pulse of ~55 pulses per second. This matches their rapid wing flapping.
The fundamental frequency was 44 kHz, with faint harmonics at 88 kHz, 132 kHz and 176 kHz. The presence of harmonics indicates the sound has a musical, tonal quality despite being inaudible to us.
Why the sound is so faint
Hummingbird wings are only around 3 inches long and their bodies are tiny. Small objects moving through the air do not displace and push around enough air molecules to produce very robust sound waves.
In comparison, larger winged creatures like geese and crows have much louder wing sounds. The large surface area of their wings pushes around far more air with each flap, creating higher energy sound waves we can easily hear.
Hummingbirds also have specially adapted feathers that minimize noise while flying. Their feathers have soft, fringed edges that help muffle the sound. The velvety surface of the feathers absorbs and dampens vibrations, reducing noise.
Finally, the airflow around hummingbird wings has been found to be remarkably laminar, or smooth. Turbulence causes noisy, chaotic air currents, but laminar flow minimizes sound generation. Hummingbirds seem uniquely adapted to fly with minimal turbulence that could create loud wing sounds.
Do hummingbirds use their wing sounds for communication?
While we can’t hear hummingbird wings, it seems possible the birds may be able to hear each other’s wing beats for communication and territorial purposes. Males defending a territory will perform dive displays during which wind likely amplifies the wing beat sounds.
However, more research is needed to determine if hummingbirds actually use their faint wing sounds to communicate while flying. Other noises like vocalizations are likely more important for communication. The faint wing beat sounds may simply be an inevitable byproduct of their specialized flying abilities, rather than serving a communication purpose.
Conclusion
In summary, high speed camera footage confirms that hummingbird wings do indeed produce sound by disturbing and vibrating air particles. However, the sounds are extremely high frequency and very low amplitude, so they are inaudible to humans.
Specialized microphone recordings have detected the ultrasonic hummingbird wing beats and shown they create a faint, tonal sound around 44 kHz. But the tiny wings and specially adapted feathers minimize noise generation, resulting in very quiet flapping. Other larger birds produce much louder wing beat sounds than hummingbirds.
While we cannot hear it, the sound is definitely there – so hummingbird wings do make noise as they fly! It’s just at a pitch beyond our hearing range. The sound likely does not serve a communication purpose for hummingbirds, but is simply an inevitable product of their unique physiology that enables hovering and backward flight.
