What it does
Young people can hear sounds from about 20 Hz (a deep rumble) to 20 000 Hz (a thin, high whine). Sounds below that are infrasound; above it, ultrasound. This page makes pure tones in your browser so you can hear the difference:
- Play any frequency on a log-scale slider (each step up the slider multiplies the frequency, like keys on a piano).
- Sweep up from 20 Hz or sweep down from 20 kHz, and press the button when you first hear the tone. The page shows the lowest and highest you marked, on a chart next to the approximate ranges of an elephant, a dog, a cat and a bat.
- For every tone it shows the wavelength in air, λ = v ÷ f.
Nothing is recorded or stored. Turn your volume down first. This is a science demonstration, not a hearing test: phone and laptop speakers can’t play very low notes, and many headphones fade above 15 kHz.
It fits the Class 9 science chapter Sound Waves: Characteristics and Applications (range of hearing, infrasound and ultrasound). What a sound wave looks like is in sound wave visualiser, echoes of sound and ultrasound are in echo and SONAR, and a live picture of the sounds around you is in audio spectrum analyser.
How to use it
- Lower your device volume. Set vol low too.
- Move the Hz slider or type a frequency, and press Play. Press Stop to end.
- Press Sweep up; when you first hear the tone, press I hear it / it’s gone. Do the same with Sweep down.
- Look at the chart: the red line is the current tone.
A worked example
At 1 000 Hz the wavelength in air is 343 ÷ 1 000 = 0.343 m. At 20 Hz it is 17.15 m, longer than a bus; at 20 000 Hz it is only 0.01715 m (about 1.7 cm). A dog whistle at 30 000 Hz is ultrasound: dogs (up to about 45 kHz) hear it, people don’t.
Tips
- Use headphones for the high end, a big speaker for the low end.
- The top of the range falls with age, which is why some teenagers hear high tones adults can’t.
- Loudness is not frequency: a loud tone is not a higher one.
FAQ
Is anything recorded? No. The page only plays sound; it never uses the microphone.
Is this the NCERT book? No. It covers the same topic with fibub’s own examples. fibub is not part of NCERT.
Where the numbers come from
- Tones are made with the browser's Web Audio API (an oscillator); nothing is recorded. Human range 20 Hz to 20 kHz and the wave relation v = fλ are standard school physics; 343 m/s is the speed of sound in air at 20 °C.
- Animal ranges are rounded, approximate general-knowledge figures for comparison only; individuals and studies differ.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-09.