Science Buddies: "Ask an Expert"

Hi, I am doing my project on the effects that the pickups have on the electric guitar. For the experiment I have done my research on nodes, antinodes, sound waves, and frequency. My question is, do I need to be able to measure where the frequencies are located on each string? I know that I need to identify the nodes and antinodes locations, but not sure if and how to locate teh frequency. Thank you for any help,
7th grade student

I don't know much about guitar pick-ups, but do no quite a bit about vibration.

It is not difficult to measure the frequency of a plucked guitar string. There are many simple methods. One is to use a tuning fork with a frequency close to the guitar string of interest and tune the string to match the tuning fork. You could also use any of the numerous on-line guitar tuner web sites to get reference tones.

There are a number of relatively inexpensive frequency measurement devices on the market that people use to tune instruments, called guitar tuners. You can even find them at WalMart. And there are much more expensive and complex instruments we use in our laboratories that can measure frequency. Perhaps your school has one in a science lab you could use.

You asked, "do I need to be able to measure where the frequencies are located on each string?". Actually, the entire string vibrates at the same frequency, with the string moving in opposite directions on each side of a vibration node. So I don't think I correctly understand your question.

I am curious how you plan to identify the locations of the nodes and anti-nodes. Please describe that to me. Thanks.

Ed, thank you for your reply. This is the procedures that I have found upon doing the research. I will also ask my teacher if he has a more advanced machine that can measure frequency, otherwise I will just use my tuner I have at home. Thank you for your help, I love to play the guitar and this seemed interesting to me, but at the same time a bit difficult. I guess that measureing the nodes and anitnodes will also be a challenge...

Measure the length of the strings on your guitar (in cm), between where they contact the bridge and where they contact the nut.
Use your knowledge of standing waves to calculate where the following are located for each string:
Location of node(s) and antinodes for the 2nd, 3rd, 4th, etc. harmonics of each string.
Frequencies (pitches) for the 2nd, 3rd, 4th, etc. harmonics of each string.
Measure the location of each of the pickups for each string.
For each string and each pickup:
Which harmonics have nodes near the pickup?
Which harmonics have antinodes near the pickup?
Which harmonics will contribute most to the sound produced by each pickup?
Which harmonics will contribute least to the sound produced by each pickup?
For each string, select the pickups one at a time, then pick the string, using the same picking motion, and the same location on the string. How does the tone of each string vary as you change the pickup?
thanks again for any help,
7th grade student from Florida

Ahhh. I see what you plan to do now. Thank you.

So, you won't actually be measuring the location of each node and anti-node, but calculating where it should be - theoretically.

The location of nodes and anti-nodes will vary slightly from theory due to things like variation in the wire diameter, temperature, and a few other variables.

If you can get access to a variable frequency strobe light, you can set the light frequency to the frequency of a particular string and actually see where the nodes are. You might want to try this. It should be very interesting.

Whatever you do, have fun!