# Does Diameter Matter

Hands On:

1) Connect a mouthpiece to two different types of materials that are both the same length but that have different diameters.

2) Do the sounds that you create with the different diameters of pipe sound different? Can you describe what changes?

3) Do the pitches change? If not, is there something else that changes?

Simple Explanation:

When you blow on the mouthpiece of your instrument, it creates vibrations down the length of the instrument. That means that the main frequency or pitch is determined by the length of the pipe or tubing that you have attached to the mouthpiece. The diameter of the pipe or tubing does not have a great effect on the frequency or pitch of the instrument.

But you might have noticed a difference in the sound of the instrument when you changed the pipe or tubing. What could have caused this? It is likely that in order to try out 2 pieces of material that were equal length but different diameters, you ended up using two different materials – maybe a rigid pipe and a soft, flexible hose. Each of these materials has different sonic properties that change what we call the timbre. Timbre is the quality of sound that makes it easy to tell if an electric guitar or a flute is making a sound, even if they are playing the exact same pitch or note.

The small differences between the sound of different materials is something to which instrument makers pay a great deal of attention. For example, many guitars are created from at least four different types of wood – one type of wood might be used for the top of the guitar, another for the edges and yet another for the back of the guitar. Each one chosen for its particular properties for its particular application.

Further Experimentation:

One advantage of these mouthpieces is that they have different outer diameters allowing you to connect to a variety of different objects. Experiment and play with different materials that you find throughout your daily life. See what kinds of unusual things you can connect to your mouthpiece.

Some Math:

The instruments that are created using our mouthpieces and pipes, should more or less follow this equation:

Frequency = SpeedofSound/(4*TubeLengthInMeters)

SpeedofSound = 340.29 m / s

Further Learning:

https://cnx.org/contents/8wb7KfA0@15/Timbre-The-Color-of-Music

http://www.studyphysics.ca/newnotes/20/unit03_mechanicalwaves/chp141516_waves/lesson51.htm