PHYS341/2023/Project6

Presentation Script

Slide 1

Hello! My name is Annika, and for my project, I will be exploring the differences between electric guitar and bass guitar. I’d like to dive deeper into what makes each instrument unique, more than the number of strings and the fact that one is harder to carry around than the other.

Slide 2

First I’ll start with some of the basics (pun very much intended) of each instrument. Both produce sound in the same way, since they’re both string instruments, and they’re both electric rather than acoustic, which means they rely on electric signals and amplifiers to make sound. After going over how both instruments make sound, I’ll get into some of the basic differences between them in terms of the physical structure of each one.

Slide 3

So the strings on a guitar are stretched between two fixed points. By default, these two fixed points are the ‘nut’ at the top of the guitar, and the ‘bridge at the bottom. When a point on the string is displaced, such as by plucking or strumming, restoring forces cause the string to oscillate back and forth, and thus a number of different standing waves occur. The frequencies of all these possible waves are multiples of one fundamental. For example, if I pluck the low E string on my acoustic guitar here (pluck string)- This E has a frequency of around 82.41 Hz, which means that the other standing waves on the string have frequencies which are multiples of 82.41 Hz, and the presence of these harmonics creates the unique timbre of the guitar.

Slide 4

Although the sound the guitar makes starts with the oscillations of the string, we know that the string by itself is too thin to cause a large enough disturbance in the air that the resulting sound is as loud as we would like. So, we’ve seen that in acoustic instruments, such as the violin or acoustic guitar, it’s important to design the instrument so that it has an air cavity inside, as well as a certain body shape, which together have natural resonance frequencies that correspond to the notes we want to play, so that each note can be amplified. However, as you’ll notice with the electric guitar and bass, they have a certain shape, but there is no hole, and a lot of the material is different. So how do we get loud sounds?

Slide 5

As the title of this slide suggests, we use things called pickups and amps to get a louder sound from our guitars. Pickups are located on the body of the guitar, underneath the strings, like where the hole would be on an acoustic guitar. Pickups consist of magnets and coils. You can sort of think of them as mini microphones which convert energy from the string vibrations into an electric signal via electromagnetic induction. This signal is then sent to an amplifier, or amp, and the sound that comes out of the amp is the final sound we listen to. However, the process of making sound goes a bit deeper than simply string + pickup + amp.

Slide 6

There are many, many ways to adjust the timbre of an electric guitar or bass. First, you’ll find that many guitars have more than one pickup, and you can also often select which pickup or pickups you want to use, as well as make further adjustments for each one. Interestingly, the location of the pickup is important. As we learned in class, the string has some set wavelengths that can occur when the string is played. Now, certain wavelengths will be more strongly detected by the pickup depending on wherer the nodes and antinodes fall. As we can see in this image on the right, if an antinode is right above the pickup, it’ll be closer to the magnet, whereas if there’s a node, it’s further away. This leads to some harmonics being more prominent than others, leading to different timbres. Musicians can select which pickups to use, as well as adjust each of them to get different timbres.

On amps as well, there are knobs which can adjust the low, mid, and high frequencies. And amps can have other settings like gain or overdrive which can adjust the timbre. For the sake of time, I won’t go deeper into these, but there are so many more options and types of equipment for changing the timbre of these instruments, so guitarists and bassists can get the exact tone that they want.

Slide 7

So now, we’ll go into some of the basic differences between the bass and electric guitar. Note that many of these details, such as string thickness, length, tension, etc. can vary, but I’ll just be going over some of the basics for now.

First, I’ll talk about the string differences, starting with the length. The maximum length of the string goes from the nut to the bridge. Since longer wavelengths get lower frequencies, we need longer strings on the bass to help us get those low notes. If we look at the frequency formula: f = v/2L, we can see that when you increase the length, the frequency goes down.

Now, another difference in the strings is that the strings on the bass guitar are much thicker. Why is this?? Let’s look at the formula again: f = v/2L. We’ve seen how the length affects the frequency, now let’s see how the velocity affects it with another formula: v = sqrt(F/μ). We want to lower the velocity, so to do that we can change the mass density. Looking at the formula, a higher mass density leads to a lower velocity. So basically, that is why bass guitar strings are thicker and longer than electric guitars! As you can see with the sample thicknesses I’ve noted here, the thinnest string on the bass is about the same thickness as the thickest one on the electric.

Slide 8

Now that we’ve gone over the differences in how these instruments are constructed, let’s look at what they can actually play. All the strings on a 4-string bass in standard tuning, EADG, match the lowest four strings on an electric guitar, but an octave lower. Since we know that octaves have a 2:1 frequency ratio, this means that if I pluck the lowest string on the electric guitar, that note will have a fundamental frequency that is twice the frequency if I pluck the lowest string on the bass.

Guitars can be tuned in different ways, but I’ll just be talking about the standard tuning for now. They can also vary in number of frets, but I’ll be using the guitar & bass that I own as examples here.

So the lowest note on my guitar is this E2, which has a frequency of about 82 Hz. The highest note I can play is C#6, which has a frequency of about 1109 Hz. The lowest note on my bass is an E1, which is about 41 Hz, and the highest is D#4, which is about 311 Hz. So the range of notes that overlap is from E2 to D#4 – almost 2 octaves.

Slide 9

Now we’ll finally start comparing the actual sounds of these two instruments. First we’ll compare the timbres & spectra and look at some of the graphs for those, then I’ll briefly demonstrate how these two instruments are used in actual music to highlight the differences between them in context.

Slide 10

To compare the two instruments, I played 3 notes: E, A, and D. I played each one on the electric guitar, then did the same on the bass, then played the bass an octave lower, since that’s usually what you’ll hear in music– the bass plays one or more octaves lower than the lowest note in a guitar chord. Just a note that like I mentioned before, the timbre of each guitar can be modified in many ways, but I just used some generic settings in my data.

Here we have the waveforms for the first note, E2. We can see by these white lines I put on the image that the wavelengths are the same on both instruments playing the same note of course, and that the one an octave lower has a wavelength which is two times that of the higher one.

This is what is sounds like on the electric: [play sound], the bass: [play sound], and the bass an octave lower: [play sound]

Slide 11

Now let’s look at the spectrum graphs for these. First we have both guitars playing the same frequency. We can see that on the electric guitar, the fundamental is not very strong, and it’s the third and second harmonics which are most prominent. There are also overall more of the higher harmonics present further along in the graph, whereas for the bass, we see less of those higher harmonics. For the bass, the fundamental is much stronger, especially compared to the fundamental on the electric.

Slide 12

Here we have the same graph for the electric guitar, but an octave lower, or half the frequency, on the bass. Interestingly, we don’t see a peak at 41 Hz on this graph, although we saw on the waveform that the frequency was half of the one an octave above, so I’m not quite sure why we don’t see it on the spectrum graph. However, we do see that the second, third, and fourth harmonics are all similar in strength, and like before we have less of those higher harmonics.

Slide 13

Now we have the same thing for the note A.

This is what is sounds like on the electric: [play sound], the bass: [play sound], and the bass an octave lower: [play sound]

Slide 14

Comparing the spectra, we can see for the electric that again the second harmonic is most prominent, and the fundamental up to the fourth harmonic are quite present, but we don’t get much of the higher ones.

For the bass we can very clearly see the fundamental and f2 as the strongest, some of the third and fourth harmonics as well, and the rest are not very strong.

Slide 15

Now we go an octave lower on the bass, and this time we can see the lower fundamental frequency, although the second, third, and fourth harmonics are more prominent.

Slide 16

Lastly, we have the same process for the note D.

This is what is sounds like on the electric: [play sound], the bass: [play sound], and the bass an octave lower: [play sound]

Slide 17

Similarly to the other notes, on the electric, we get f2 as the most prominent harmonic, though we can see many other harmonics are present as well.

On the bass, we see the fundamental is the highest, and we can also see a lot of f2 and f3, and some f4, but the rest are not very present at all.

Slide 18

As we go an octave lower on the bass, similarly, we see the first four harmonics are quite strong, but not much higher than that.

Slide 19

So now that we’ve compared the notes by themselves, let’s look at how the sound wave looks when we combine the electric and the bass. Here I’ve combined the electric playing A2 with the bass playing an octave lower, on A1, and you can see the combined waveform and spectrum graph here, and this is what they sound like together: [play sound]

Looking at the spectrum, we can see that it looks a lot like the bass spectrum, (probably since I ended up playing the bass a bit louder) but some of the harmonics, like f4 onward are a bit stronger. In particular, the fourth harmonic went up quite a bit. This would correspond to the second harmonic on the electric guitar’s spectrum, and we can see that that one is the strongest for the electric– so we see that reflected in the combined spectrum.

Slide 20

Lastly, I’ve played some simplified examples to demonstrate a couple of different ways that the bass and electric guitar normally combine in music. First, we have bass notes playing with electric guitar power chords as well as a lead electric melody. The harmonic series of a bass note playing the root note of the chord an octave lower contains harmonics for the notes in the chord that the electric guitar plays, so the bass is really good at supporting those chords. Like we saw a bit earlier, the electric can play much higher than the bass, almost two octaves more, so the higher melody of the lead guitar can stand out very nicely.

So as an example, here’s how I played the intro of That’s What You Get by Paramore: [play audio]

Of course, if you listen to the actual song, it sounds much better than that, but here I only have two guitars and a bass as a simple demonstration of how each instrument is used.

We can also sometimes hear the two playing the same part, but the bass going an octave lower. This can highlight the uniqueness of the sound of each instrument, and it’s very cool to hear them working together. As an example of this, here’s how I played the intro of Still the One, originally by Shania Twain reinterpreted by Jesse Barrera: [play audio]

Now I didn’t really pay attention to adjusting the timbre of my instruments much for these recordings, nor do I have any equipment for the effects that you’d hear in the original songs. So just imagine with better knowledge and equipment how much musicians can do by modifying their timbres to get their desired sound! Each instrument has its own capabilities and strengths, and together with other instruments, so much beautiful music can be made.

That is all for my very limited exploration of these two instruments :> Have a great day and enjoy some good music! <3

Works Cited

Barrera, J. (2022, July 15). Still The One [Song]. THE JB CAVE Records.

Bell, E. (n.d.). The Ultimate Bass Guitar Strings Guide - Information You Need to Know. StringVibe. https://www.stringvibe.com/bass-guitar-strings-guide/

Duffy, M. (n.d.). Electric Guitar String Buyer’s Guide. Fender Guitars. https://www.fender.com/articles/instruments/fender-electric-guitar-string-guide

Eric. (2023, January 5). How Pickup Placement Affects The Sound Of Your Guitar. FuelRocks. https://www.fuelrocks.com/how-pickup-placement-affects-the-sound-of-your-guitar/

Owens, J. (n.d.). How to Use the Stratocaster Pickup Selector Switch. Fender Guitars. https://www.fender.com/articles/instruments/sounds-aplenty-the-stratocaster-pickup-selector-switch

Paramore. (2007, June 11). That's What You Get [Song]. On Riot!. WEA International Inc.

Sobolev, J. (n.d.). How Do Guitar Amps Work? Simply Explained, Easy To Get. Rock Guitar Universe. https://rockguitaruniverse.com/how-guitar-amps-work/

Suits, B.H. (n.d.). Frequencies of Musical Notes, A4 = 440 Hz. Physics of Music - Notes. https://pages.mtu.edu/~suits/notefreqs.html

WikiAdmin. (2019, December 20). How do Guitar Pickups Work? Everything You Need to Know. WikiAudio. https://www.wikiaudio.org/how-do-guitar-pickups-work/

Yamaha. (n.d.). The Structure of the Electric Guitar : What are pickups? - Musical Instrument Guide. https://www.yamaha.com/en/musical_instrument_guide/electric_guitar/mechanism/mechanism002.html

Slides for draft submission

https://docs.google.com/presentation/d/1lzgt_9UoRvgu9y2FR7ICEw3YuVSEhhdicCRbl49YhdI/edit?usp=sharing