Waves - hear, Piotr Nieżurawski, waves.pionie.com/hear

Waves - hear

Version 2018-02-21

f1 = Hz

λ1 = cm


  Left Right

f2 = Hz

λ2 = cm


  Left Right

Phase, φ / (2 π) = shift / λ2

Assumed speed of sound, v = m/s
λi = v / fi

Experiment with the sound!

Change frequency, volume, panning and relative phase of two sound sources producing sinusoidal waves.

For fine-tuning use the left and right arrow keys.

Use headphones or loudspeakers.

Puzzles and problems

Solve puzzles and problems

For some of the puzzles headphones are enough.

For some of the problems loudspeakers are necessary. Put them at the table edge, far from walls and other obstacles.

Waves - see

Visualize your sound experiments with Waves - see animation! Use proper relative values of wavelengths and the distance between sources. Remember about the phase.


Use your ears - sometimes it is better to use only one of them. Or measure the sound intensity with your smartphone (install appropriate app).

Useful key combinations

  • Ctrl-F5 Reload window, reset values in the form to their default values
  • F12 Console on/off

  • Shift-F5 Reload window, reset cache
  • F12 Console on/off

Read the console output if the program fails.


The program is available for free, under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

Archive to download

Author, contact

Piotr Nieżurawski
Pionie EN

Local usage

You can also use this program locally, without internet connection.
Quick start:
  • unpack the archive
  • open the file Waves-hear/waves-hear.html in the browser
In Linux terminal:
$ tar xf Waves-hear[...].tgz
$ cd Waves-hear/
$ firefox waves-hear.html
$ chromium-browser waves-hear.html

Puzzles and problems

At each puzzle or problem it is assumed that you start with the default values of the volumes (50%), the frequencies (220 Hz), the pannings (0) and the relative phase (0). Either set these values or reload the page.

To make it easier, open this page in the next tab: Ctrl-click or right click and "Open link in new tab" on Switch between tabs:
Ctrl-Tab - go forward
Ctrl-Shift-Tab - go back

Puzzle (mono)

Everyone works, but...

headphones or loudspeakers
Silence the sound by changing only the phase.

Puzzle (mono)

1 > 2 ?

headphones or loudspeakers
Set the phase control to 0.5 (then there should be no sound). Do not touch volume, panning and phase controls, and do not change frequency values. How to get the sound, with such restrictions?

Problem (mono)

220 + ...

headphones or loudspeakers
Produce beats by changing the frequency of one of the sources. Observe the dependence of the beat frequency on the difference |f1 - f2|. Measure the beat frequency with a stopwatch.

Problem (stereo)

Feel the phase

Set the panning of the first source to -1 (left) and of the second one to 1 (right). Scan the phase values. Do you observe a difference? Change frequency values, always f1 = f2. Scan the phase values. Isn't it amazing that we feel the phase difference between our ears?

More puzzles and problems soon

  Author: Piotr Nieżurawski