A penny whistle (or Irish whistle, etc.) uses a vibrating stream of air that resonates inside of a tube of a given length to produce sound waves at a given pitch. The distinguishing feature of a penny whistles as compared to other types of flutes is that it uses what is called a fipple to produce the vibrations. A fipple is a type of mouthpiece where a stream of air is blown through a channel and cut by a blade, which allows a thin sheet of air to pass beneath the blade. The fipple makes it easy for the player to set up the vibrations, but gives the player less control over shaping the note, as compared to say, a flute. Below is an animated GIF of a fipple producing vibrations, from Air Vibrations in a Recorder (in Dutch).
We will be fabricating whistle mouthpieces (fipples) on a 3D printer and attaching them to lengths of PVC tubing (1/2" schedule 40 tubing). Below are resources for designing a whistle.
The pitch or frequency of the note produced by a whistle depends on the tube length, where the shorter the tube, the higher the frequency, or more specifically, the frequency is proportional to 1/(tube length).
By cutting holes into the whistle tube, you effectively shorten the tube, raising the pitch. By carefully placing the holes and covering them with your fingers, you can create an instrument that can play the notes of a scale. A traditional Irish Penny Whistle has 6 holes tuned to play a D major scale.
Irish whistle fingerings:
To make an Irish whistle in D that will be properly in tune using our mouthpiece follow these steps:
This particular whistle plays a D note. If overblown, it will play the D an octave higher. The sound of the whistle is pleasingly rich, as illustrated by the frequency spectrum and oscilloscope waveform below. Here the whistle is blown hard enough to the point before the octave break. The spectrum show a main peak at 595 Hz, with a second beak an octave above at 1190 Hz. It also has overtones above that, which contribute to the rich sound. The oscilloscope waveform clearly shows the presence of the fundamental frequency and octave above.
A log drum consists of a resonant box with a top striking surface with two different sized tabs. The two tabs produce two different notes when struck. This log drum was designed as a set of interlocking plates in Inkscape and then cut on a laser cutter.
This set of chimes is made from 3/4" EMT galvanized steel electrical conduit. The base is 1/4" plywood, cut using a laser cutter. The chimes are supported at their nodal points on sections of foam pipe insulation.