If you have ever taken a break from your oboe practicing to think, “Ya know, this is just like airplanes,” then you are probably a special kind of person, but you are not wrong! The same physics makes both possible! Here is how an oboe reed works:
The Sciency Principle
Bernoulli’s principle is the star of the whole process. Bernoulli’s principle is that the faster a fluid is flowing, the less pressure is in the fluid. And, inversely, the more slowly a fluid is flowing, the more pressure it has. Also included in this principle is that a greater volume of moving fluid has more pressure than a smaller volume.
You probably learned this principle in school with a plane as an example. The wings are shaped so that air moves more slowly under the wing than over it. Therefore, there is more pressure under the wings of the plane pushing it up into the lower pressure above the wings.
You might already be seeing how this affects an oboe reed except there are two “wings.” When blowing through the reed, the fast moving air inside the reed creates a low pressure area. The higher pressure from the still air outside the reed now presses the two blades of the reed together. But now that the path for the air, the inside of the reed, is more narrow, a smaller volume of air is moving through the reed and the pressure inside the reed is raised again. This pushes the two blades open, usually so far as to not be touching at the corners of the reed. Then the process begins again as the pressure inside the reed decreases and increases alternately.
What This Means
This whole cycle is what creates the sound waves we hear as notes. When playing the note A at 440 Hz, the reed goes through the above process 440 times per second. It happens more quickly for higher notes and more slowly for lower notes.
The changing pressure in the reed causes the air coming out of the reed, whether into the air or into the oboe, to be at alternating high and low pressures as well. This is what causes a reed on its own to sound like it is buzzing – the higher and lower pressures create different alternating sounds. This is also what creates the air movement necessary for the oboe to play in the rest of the instrument, but we will save that for another day!
The Material
This rapid slamming together and springing back open hundreds of times a second is what makes the material for reeds so important as well. It needs to have the flexibility to perform this without immediately cracking, but also the rigidity to not flap like a flag in the wind. Therefore, cane has yet to be widely replaced with a comparable substitute, despite the fact that being played does cause the reed fibers to break down pretty quickly.
How long a reed lasts varies widely. Cane with more densely packed fibers will last longer than less dense cane, and cane that grows more slowly will be more dense. But, cane is usually harvested by height and not by how fast it got there, so the differences in every piece of cane are largely due to this.
And that’s how an oboe reed works!
Read more about this from this project, Effects of Time on the Sound Quality of Cane Oboe Reeds by Zachary Everett Blais and watch a really great video animation of this happening while playing from the Yamaha website here.
Also, check out my oboe reed shop here!