science · FOLLOW YOUR CURIOSITY
What changes when a note rises an octave?
Two short tones reveal a relationship you can hear. Try them, or follow the explanation without sound.
Explore the interactive discovery →
Frequency can be measured
Hertz counts cycles per second; pitch is what you hear. Compare the three values below: the jump from 220 to 440 is 220 hertz, while the next jump is 440 hertz. Both are an octave because the ratio stays the same.
Compare three frequencies
Starting tone
220 cycles per second.
220 Hz
One octave higher
Twice the starting frequency.
440 Hz
Two octaves higher
Four times the starting frequency.
880 Hz
These are pure synthetic tones. They do not reproduce an instrument’s timbre, harmonics or a real recording.
AN IDEA TO TAKE WITH YOU
An octave doubles frequency; it does not add the same number of hertz each time.
Follow a connection
Can adding sound make things quieter? →
You changed frequency to compare pitch. Now keep frequency fixed and compare the timing of two waves.
Sources and transparency
UNSW · Frequency and pitch
Accessed: 2026-11-02
Open University · Octave pitch and frequency
Accessed: 2026-11-02
OpenStax · Math and music
Accessed: 2026-11-02
Illustrations explain an idea. Sources are available above.