The Acoustic Beating Widget demonstrates how two nearly tuned tones will produces a pulsing beat that you can actualy hear. By moving some of the controls around with your mouse (or quicker on a computer keyboard) you can listen to and see acoustic beating. A frequency spectrum and sound wave envelope display help you see what you are hearing.
Click the play button to listen to the tones. The space bar (or clicking the button again) will pause the tone. By default two tones is running: A & B. Typically you’ll only change first tone (A), with the second tone being a reference. To determine what tone is active when you nudge the keyboard, simply click on the card associated with either Tone A or Tone B.
How to Use the Widget
Select the tone whose pitch you wish to alter using the sliders. To change fundamental frequency use coarse slider. For small adjustments (in hertz) use fine slider that increases or decreases by a tiny amount. Alternatively enter a desired frequency directly into number box.
Click the Solo button if you’d like to hear just this single tone. Press the Mute button to switch off the tone altogether. Use the Level slider to adjust the volume of each tone independently. Top control is for master volume.
Below this are buttons which alters the type of wave being generated. Square, triangle, sine, and sawtooth waves has different tones. They have different amounts of harmonic content, which leads to more interesting interweaving patterns.
Choose from several view modes, including Spectrum view, Envelope view, and Spectrum + Envelope view. The spectrum view illustrates the breakdown of frequencies into individual components, whereas the envelope view demonstrate how they pulse through time.
The interval buttons allow you to snap tones into a chosen musical interval. In this case, it sets Tone B based off the ratio of Tone A to Tone B using just intonation. The Make it beat button then applies a tiny detune to show how those two tones will beat in that interval. The cent shift buttons lets you manually detune Tone B by tiny amounts to vary the rate of the beat.
It has three different types of ear training exercises. The first is the tune challenge where you have to find Tone B, which is slightly out of tune and hidden. You need to adjust Tone A until it doesn’t beat anymore, then see how accurate you are. The second is the string tuner where you try to turn a slider until it matches a hidden reference note like a tuning peg would. The final one is called the counting game where you hear the beats and need to pick the right rate from a list.
You can adjust more precisely using keyboard shortcuts. Press A or B to select the active tone. Adjust the frequency up/down by pressing on the arrow keys. Solo a tone (S) or mute it (M). Switch between views (V), cycle through waveforms (W) and tune the tones in unison (U). Start or stop the counting game (C). Start or stop the tuning challenge (T). Reset all settings (R).
For example, alter the waveform and listen as you observe how the harmonics impact on the beating. When using sine waves the beat rate is precisely equal to the difference between frequencies. For more complex waveforms other combinations of harmonics will be beating against each other at different rates. You can find out which ones by looking in the spectrum view. It’s a good way to develop an intuitive grasp of what is dissonance and what isn’t when it comes to intervals.
The presets enable you to easily configure commonly used beat rates. You can then compare a rattling, fast pulse to a smooth, slow one. Try dragging the fine slider towards zero and hear how the beat rate reduces to nothing. If all the tones are perfectly tuned, the envelope will flatten out into a straight line. This provides clear visual feedback that confirms what you hear.
It automatically adapts to your color scheme and screen size. If you’re on a small screen, just tap “Fullscreen” to get more space to work with. For more information about using the modes, hit the help panel. This explains how it works and the physics behind it.
Spend some time playing around with the controls. Pretty soon you’ll have a keen ear for the small details in tuning and pitch.