Basics

Plucking a string, part 1

Using one of our guitars, we look at a frequency analysis of the sound they make. Nothing surprising to anyone who knows even a little about acoustics, but starting this project about 20 instruments ago, we knew nothing! Amplitudes and frequencies mostly.

--------------------------------------------------------------------------------------------------------------------------------------------------------------

Note B2 (123.47 Hz) with a variable number of harmonics. Be patient!

Summed sin waves with equal amplitude and phase. The slider will control the number of harmonics, NT. Wait for blue bars to appear, then start (arrow). After changing the slider (which changes NT) wait for blue bars to appear before restarting. Note that more of the higher harmonics produces a more dissonant sound: Harmonic frequencies are not all close to a recognized note frequency, and even when they are, they are not part of a recognized chord.

-------------------------------------------------------------------------------------------------------------------------------------------------------

Waves on a string; change where you pluck (x1r) and run it (t)

Animated string, fixed pluck position

Waves on a guitar string. This first button ("Waves on a string…") plots the string displacement along the length of the string from bridge (left) to nut (right). Change where you want to pluck using the x1r bar, from the bridge (left hand side) to the middle, and then drag the time bar to watch how the oscillations reflect at the bridge and nut. Or watch the animation for a fixed pluck location, at 29% of the distance from the bridge to the nut.

-------------------------------------------------------------------------------------------------------------------------------------------------------

Notes on a stiff string

Guitar strings are stiff, and when you include this in the calculations, you find the harmonics are sharp. This only matters for higher harmonics when playing up the neck on the lower strings, and even then we don't know if our ears could pick out the differences amongst the lower harmonics with more power.

-------------------------------------------------------------------------------------------------------------------------------------------------------