Start with your device volume low. Very low tones may be inaudible on phone or laptop speakers; very high tones can be uncomfortable on headphones.
What does 91 Hz sound like?
91 Hz is a bass frequency. It is a low bass tone – a warm hum similar to the low strings of a cello or bass guitar. Phone speakers reproduce it weakly; headphones work much better.
A 91 Hz sound wave completes 91 cycles every second, so one cycle lasts 11 ms. In air at 20 °C, where sound travels at about 343 m/s, each wave is 3.77 m (12.37 ft) long; in water it stretches to 16.27 m because sound moves about 4.3 times faster there.
Musically, 91 Hz is 28 cents below F♯2 (92.5 Hz) in standard A440 tuning. Doubling it to 182 Hz raises the pitch by one octave; halving it to 45.5 Hz lowers it by one.
Wavelength of 91 Hz in different materials
| Medium | Speed of sound | Wavelength |
|---|---|---|
| Air (20 °C) | 343 m/s | 3.77 m |
| Fresh water | 1,481 m/s | 16.27 m |
| Seawater | 1,500 m/s | 16.48 m |
| Helium | 1,007 m/s | 11.07 m |
| Steel | 5,960 m/s | 65.49 m |
| Glass | 5,640 m/s | 61.98 m |
Harmonics and octaves
Real instruments playing 91 Hz also produce harmonics at whole-number multiples of the fundamental. Their relative strength gives each instrument its timbre.
Which animals can hear 91 Hz?
Can hear it
Humans, Dogs, Cats, Horses, Cows, Pigs, Goats, Guinea pigs, Ferrets, Chinchillas, Elephants, Bottlenose dolphins, Tree frogs, Goldfish, Catfish, Tuna
Cannot hear it
Sheep, Rabbits, Rats, Mice, Gerbils, Hedgehogs, Raccoons, Opossums, Bats, Beluga whales, Chickens, Canaries, Budgerigars (parakeets), Cockatiels, Owls, Bullfrogs, Greater wax moths
Instruments and voices that can play 91 Hz
Frequently asked questions
What does 91 Hz sound like?
It is a low bass tone – a warm hum similar to the low strings of a cello or bass guitar. Phone speakers reproduce it weakly; headphones work much better.
Can humans hear 91 Hz?
Yes. 91 Hz is inside the typical human hearing range of 20 Hz to 20 kHz.
What musical note is 91 Hz?
91 Hz is 28 cents below F♯2, which is 92.5 Hz in standard A440 tuning.
What is the wavelength of 91 Hz?
About 3.77 m in air at 20 °C and 16.27 m in water.
Can dogs hear 91 Hz?
Yes – dogs hear roughly 67 Hz to 45,000 Hz.