how does pipe length of a wind instrument change the frequency of the vibration, especially in brass and reed instruments where you have a physical object vibrating, rather than just the air?

Question

I get that the length of the pipe affects the wavelength of the sound wave, but I’m curious how that forces the player’s lips, or reed to vibrate at different rates

In: 4

Answer 1

That’s a great question! The length of the pipe in a wind instrument, such as a trumpet or a saxophone, determines the wavelength of the sound wave that is produced. The wavelength is the distance between two consecutive peaks or troughs of a sound wave. Longer wavelengths correspond to lower frequencies and shorter wavelengths correspond to higher frequencies.

When a player blows air into the instrument, the air inside the instrument starts to vibrate. In brass instruments like trumpet, the player’s lips vibrate to create the sound wave. This vibration is called the “lip vibration”, also known as “buzzing”, and it’s what produces the sound. The length of the instrument determines the frequency of this lip vibration, and thus the frequency of the sound wave that is produced. As you change the length of the instrument, by pressing the valves or moving the slide, it changes the frequency of the lip vibration, making the sound deeper or higher.

In reed instruments, like clarinet or saxophone, when you blow air into the instrument, it causes the reed to vibrate. The length of the instrument and the opening and closing of the keys, changes the length of the tube that the air travels through and the pressure of the air. This changes the frequency of the reed vibration, which changes the frequency of the sound wave that is produced. This is how the player can play different notes.

In summary, the length of the instrument and the position of the keys and valves, affect the wavelength and frequency of the sound wave that is produced, which changes the rate at which the player’s lips or reed vibrate and thus the note that is played.