User:JesseStone
I created a Wikipedia page but it was removed because apparently it is original research. I'd like to preserve the text, however, so here it is:
Guitar tuning with fluorescent lamp
[edit]It is possible to tune a string instrument using a fluorescent lamp. When tuning an instrument in a room illuminated by fluorescent lights, and where an electronic tuner and tuning fork are not available, this is an easy and accurate technique.
In standard guitar tuning, the A string is tuned to 110 Hz. In countries that use 60-cycle-per-second (60 Hz) AC electric power, such as the United States, fluorescent lamps flicker at the rate of 120 times per second. Since the string moves back and forth 110 times each second, and the light illuminates the string 120 times each second, the string will appear to move back and forth at a beat frequency of 10 times each second. A properly tuned A string therefore appears to flutter at 10 Hz (120 Hz minus 110 Hz) when plucked under fluorescent lights.
The following table shows the beat frequencies of the next few notes of the chromatic scale. The beat frequency is simply the difference between the note frequency and the lamp frequency (120 Hz).
| Note | Fret | Frequency | Beat frequency |
|---|---|---|---|
| A | 0 | 110.00 Hz | 10.00 Hz |
| A# | 1 | 116.54 Hz | 3.46 Hz |
| B | 2 | 123.47 Hz | 3.47 Hz |
| C | 3 | 130.81 Hz | 10.81 Hz |
| C# | 4 | 138.59 Hz | 18.59 Hz |
| D | 5 | 146.83 Hz | 26.83 Hz |
Notice that A# and B have very nearly the same beat frequency, about 3.5 Hz. Although it would be difficult to tune the string by counting the number of beats each second and requiring this number to be 3.5 when fretting the first fret on the A string, it is easy to discern whether two notes have the same beat frequency.
To tune the A string, one can therefore simply tighten the string until notes plucked on the first and second frets show the same beat frequency. That is, the string is in tune when A# and B appear to flutter at the same rate when viewed under a fluorescent light.
Additional strings can then be tuned to the A string.