How Music Works - The Physics

stuff that leverages what we've learned. We can even leverage how the universe works without having a full understanding of the scientific principles. Though in general, the better we understand those principles, the better technology we can make. And one subset of technology that I think really illustrates this well is musical instrument and so in this episode and in the next episode, I'll talk about the science behind music without getting too deep into musical theory that's its own thing,

and how musical instruments are an example of physics and action. Now, in the past, I've done episodes on stuff like synthesizers and electric guitars and pickups and amplifiers, you know, describing how electronics gave musicians new ways to make sounds, including sounds that have never been created before. But honestly, the entire history of musical instruments kind of follows that path. It's just that some of those instruments are the kind that you plug in or that you connect to amplifiers

or whatever, and some aren't. But they all relate back to science in some way or another. Music marries the scientific with the creative, and it's one of the manifestations of ingenuity that I really love. Case in point, the inspiration for today's episode came out of something I was genuinely curious about out myself. See, I'm not a musician by any stretch of the imagination. Though I do own a few musical instruments, I was never in band or

orchestra or anything like that. So I was sitting there thinking, how the heck does a trumpet work? And I researched it, and then I thought, you know, I should do a tech stuff episode on this. But then I kept going down the rabbit hole and decided to do something a little more ambitious than how a trumpet works. So in today's episode, I'm going to talk more generally about music

instruments and how they work. By explaining the physics behind the art of music, because when you get down to it, a musical instrument is really just taking what we understand about physics, building a real world object based on that understanding, and then putting it to use to make something beautiful or interesting, or, in my case, terrible. To understand all this, it's best to start with a scientific breakdown of the

phenomenon of sound. And there's an old philosophical question that says, if a tree falls in the forest and nobody is around to hear it, does it make a sound? Now, one point of this question could be to say, if there's no way to observe something happening, can we really be sure that it actually happened, particularly something as ephemeral as sound, So if no one was there to observe it,

can we say for sure that something observable happened. But another way that we could look at the same question is to say, is sound really a thing if there is no one there to perceive it? Because sound is really describing how our brains process incoming fluctuations of air pressure. In this case, we're not necessarily asking if the vibrations from the tree happened or not. It's more that if there is no one to experience that as sound, would we really say that a sound happened? Is the experience

necessary to call it sound? Now I don't have an answer to that question, but I do want to talk more about what's going on with sounds. So at the very heart of it, sound comes from vibrations. Generally, when we talk about sound, we typically mean it comes from vibrations of air molecules, which gets to that fluctuation and air pressure that I was talking about. It's fluctuations and air pressure that ultimately are sound most of the time

when we're talking about it. Sound can actually travel through really any physical medium. It's just that it travels more easily through some rather than others. And the way we usually encounter it is through the air. So let's say for a moment that you have the incredible superpower to zoom and enhance your vision, and you can also see air molecules, so you're actually looking at the air molecules

all around you. Now, imagine that you see someone clap their hands, and as they clap their hands, they're causing a bunch of air molecules to bounce around into each other, and that creates a chain reaction that passes from the point of origin, that being the clapping hands outward like a ripple and a pond, almost but in all directions. Now you're paying really close attention, and you notice that as the collisions move outward, the reaction as a whole

begins to appear to lose energy. So the further you out from the point of origin, the less you'll see those air molecules move, and eventually you'll be far enough out where the movement is imperceptible. And this is why sounds are louder when you're closer to the point of origin, which I admit is about as basic an idea as

I can communicate. But the reason those sounds are softer when you're further away, assuming you don't have some interesting curvature of the acoustic area around you, the reason that they're softer is that the energy of that initial vibration gets diluted as the reaction passes outward. And you can think of it as the origin of the sound affects a relatively small number of air molecules and at least surrounding that point of origin, and it causes those air

molecules to fluctuate. Those fluctuating air molecules cause a larger number of surrounding air molecules to fluctuate. But because you're talking about transferring energy from a smaller number of molecules to a larger number of molecules, the amount of energy transmitted to that second group of air molecules means that each individual molecule is getting less than the first group.

You know, energy cannot be created or destroyed, so we're not getting rid of energy here, it's just we're spreading it out across a larger area, so each individual component is getting slightly less energy than the previous group. Now, of course, in the real world it's not quite so neat and simple as saying a circle of air molecules than affects and slightly larger circle that affects a slightly larger circle, and so on. But you get the idea.

When we talk about vibrations, we mentioned stuff like frequency, and that word is all about the number of times a repeating event occurs within a given unit of time. So with sound, we usually refer to frequency in terms of units called hurts, h, E, R, t z. This tells us how many times this particular repeated event, and oscillation happens within the span of a second. Twenty hurts, which is generally said to be the lower end of the typical range for human hearing, would be a wave

that's oscillating twenty times per second. Any vibration slower than that would be at such a low frequency that the average person would be unable to hear it. A twenty killer hurts sound, which is at the tippy top end of typical human hearing, would mean that the oscillating wave is oscillating at a speed of twenty thousand times per second.

So that means if you had a string that vibrated at twenty hurts, you can set up a high speed camera on that string, and when you pluck the string and you're use that high speed camera to shoot video of it, you would see that for every second in real time that passes, you could count the string making twenty full cycles, which means going up and down past the camera that's one full cycle. Not just passing it once,

it has to pass it twice. That would be twenty hurts. Now, we also tend to talk about sound waves, and this gets a little complicated because we can mean different things by sound waves. We could be talking about the actual physical wave of air fluctuations that propagates outwards from the origin of sound, or we could be talking about a visualization of the qualities of a sound. And this gets into a territory where it's tricky to explain this without

visual aids, but we're gonna try. So we're gonna talk about the visualization without visual aids. So I want you to imagine that you have a piece of paper, and across the middle of this piece of paper, you draw a straight horizontal line from left to right goes all the way across the paper. And this law line in this particular representation is going to represent time. This is the X axis. So the left side of your paper, where you're starting point is, represents zero seconds. The far

right sign represents some arbitrary point of time. We'll get to that in a second, because it all depends on the specific kind of wave you're drawing. So now let's just imagine drawing a nice sign wave, and we start on the leftmost side at the center point, so zero at the center horizontal line, and draw a nice gentle crest up and then we come back down cross that center line and then draw an equally gentle trough that is of equivalent size to the crest on the opposite side.

And then once the line comes back up and crosses the horizontal line again, we've got one wavelength of a sound wave that this would be in what we would call the time domain. The reason we call it the time domain is that we are visualizing a sound wave with regard to the passing of time. That X axis again is showing the time is passing. So the wavelength describes the distance or the amount of time that passes

between two corresponding points on a sign wave. So let's say we draw a series of these like we get twenty sheets of paper, and we draw equal sign waves on each of those twenty sheets of paper, and we put them all side by side, so we get a nice continuous wave all the way down these twenty sheets wide. And we say that each sheet represents one twentieth of a second, so that when we have twenty of them side by side, that represents one seconds worth of time.

You would say I have twenty wave lengths that span one second. That means that this represents twenty hurts. This is a sound wave with a frequency of twenty Hurts because it takes twenty of these will pass a given point in space within the span of one second. So then we need to talk about the period of a wave, and this is the inverse of Frequency is the amount of time it takes for one wavelength to complete one cycle.

So frequency is the number of cycles per second. The period of a wave is the number of seconds per cycle. So for a twenty Hurts frequency, the period of the wave would be one seconds per cycle. That's why we would need twenty sheets of paper with just one nice curvy wave on each piece to represent a twenty Hurts wave. Now you could just do this on one sheet of paper, you know, you just change the scale. So you change the scale so that every single wavelength represents of a second.

You draw twenty of those on one sheet of paper. Will be much smaller than our original example, but that would still will be a twenty Hurts wave. It's all dependent on the scale of your representation. Wavelength and frequency are related, and we see that in an equation where we say velocity equals wavelength times frequency. So velocity describes the speed and direction. But we can ignore that for now of a wave as it passes a stationary point. So if we know two of those three factors, we

can figure out the third. But just a little math, right, If we know the velocity and we know the wavelength, well, we can divide the velocity by the wavelength and then we have the frequency. Or if we know the frequency but not the wavelength, we can divide the velocity by the frequency. We get the wavelength. If we know the frequency and the wavelength, we multiply them together, we get

the velocity. Pretty easy stuff. Now, speed of sound is not that difficult for us to to get our minds wrapped around, because we know what the speed of sound is generally speaking, so the speed of sound depends partly upon the medium through which the sound is traveling. Sound moves at different speeds through water than it does through the air, for example. But even in the air, stuff can affect the speed of sound, like the air's humidity

and its temperature. Essentially, we're talking about density. The density of those air molecules will affect how quickly sound can travel through it. So when we talk about the speed of sound, we have to get more specific. So we tend to describe the speed of sound as being three hundred forty three meters per second in dry air at

twenty degrees celsius. Now, for my fellow Americans out there who ain't got time to truck with no sensible metrics system or celsius or anything, this would mean sound travels at about one thousand, one twenty five ft per second when the air is sixty eight degrees fahrenheit. Sound at all frequencies will travel at the same speed through any given medium. So that means that a low pitch sound and a high pitch sound will both cover the same amount of space in the same amount of time through

the same medium. But low sounds have low frequencies and thus longer wavelengths than high sounds, which are higher frequencies with shorter wavelengths. It will take the same amount of time for a high pitch note on a trumpet to get to you as a low blast note on a tuba that's played at the same distance, but the high pitched note will have a higher frequency and a shorter

wavelength than the tubus note. Now I've used this analogy several times before, but imagine that you've got a two lane highway and you've got a line of buses that are in the right lane, and the buses are one right after the other. And in the left lane you've got a line of compact cars. And for every bus, you can fit three cars in that same length of space. And the front of the first car is in line with the front of the first bus. The rear bumper of the last car lines up with the rear bumper

of the last bus. Both lanes of traffic are traveling at the exact same speed. Down highway, both lanes of traffic will cross a finish line at the exact same time. However, you have more cars in lane two than you have buses in lane one. Everyone's going at the same speed. That's kind of the way we have to think about sound waves and frequencies. If a sound is low enough, we may not hear it at all, But if it is a strong enough signal, meaning it has a great

deal of amplitude, we could physically feel it. You remember, it's air fluctuations, it's actual air pressure. So typically we would perceive amplitude as volume, and in our sketch of a wave, it would mean that the peaks and low points would be really far out from that center line, you know, the taller those peaks are, the greater the

amplitude or greater the volume. If you've ever been near a massive sub whiffer and you felt pressure, like in your chest, but you couldn't really hear anything, chances are it means the sub whoffer was blasting out vibrations below your threshold of hearing. Typically, when we talk about music, we talk a lot more about frequencies than we do about wavelength and that's because of this relationship between frequency

and pitch. But wavelengths are also important as they will become a key component of stuff like resonance and harmonics and boyality. Let me tell you, preparing this section of the podcast was a heck of a thing all by itself, because this is stuff that's way easier to explain with visual aids. But stick with me because I know you guys are smart enough to suss it all out, so it really just falls on me to describe it clearly.

So another thing we need to understand before we jump into that, and we'll take a break before we get to resonance and harmonics. But one other thing I want to explain is the phase of a wave. A wave's phase refers to how it is offset from some specific starting position. And it really becomes important when you're talking about multiple waves. Because multiple waves can be offset from one another. They can be out of phase with each other,

and that affects the sounds that we perceive. So, going back to our original sketch of a single wave, imagine that you draw a new wave using that same series of pieces of paper, but you use a different color for this new wave, and you offset it a bit. So instead of starting at the far left of the first sheet, let's say you start one inch in so it's offset from that first wave. Otherwise it follows the exact same trajectory. Well, these two waves would be out

of phase with respect of each other. Why is this all important? I'll explain in a second, but first let's take a quick break. Okay, So before the break, I talked about the phase of a sound wave. Imagine you've got two of the same frequency of sound, but they're out of phase with each other. That would affect how we perceived the sound. It could get pretty noisy. Actually.

If the two frequencies, however, are perfectly opposite each other, so that the crests in sound wave a match up perfectly with the troughs of sound wave B, and they're of the exact same frequency and amplitude, we wouldn't hear the sound at all because those two sound waves would cancel each other out. You can think of it in

this way. Think of air molecule number one is pushing to the right on air molecule number two, but air molecule two is pushing just as hard on the left to air molecule number one, which means neither air molecule will actually move. This is how noise canceling headphones work.

By the way, the headphones incorporate a microphone. It picks up the ambient sounds in your environment, and then speakers in the headphones generate the equal but opposite sound waves to cancel out the ones that you would otherwise hear as long as the latency that being the lag between detecting a sound and generating the opposite sound, As long as that latency is low enough, we humans are too slow to pick up on the difference, and our perception

is really limited in that way. But the out of face stuff also matters a lot when we talk about things like resonance and harmonics as well. So I guess there's no time like the present to finally get into all that stuff. It is incredibly important with musical instruments, So the descriptions I've used so far really refer to pure pitches, which is something we can generate with electronics, but it's not typically what we get with musical instruments

outside of things like tuning forks. A pure pitch describes a single frequency with no harmonics or overtones, so we don't get any other frequencies other than the base one, the fundamental frequency. We're getting a pure tone, which we could plot as a smooth, consistent sign wave with equal crests and troughs, nice and neat, kind of like the example I was describing at the top of this episode. But in the real world, the sounds we hear typically

consist of more than one frequency. There are multiple frequencies going on here. We can still plot the sound waves, but they wouldn't look like those nice, smooth curves we were talking about earlier. They would be funk looking potentially, with little dips and bumps and the crests and troughs. And that's because we'd be representing a collection of frequencies in a single way. Visualization sort of the visual equivalent of how we would perceive the sound through hearing. So

let's go through with an example. Let's say you're strumming a guitar string, and that string will vibrate and not just one frequency, but a few different frequencies all at the same time. All of these frequencies are resonant frequencies, meaning these are the collection of vibration speeds at which that string naturally experiences when it is strummed. However, human hearing is such that we typically only hear the pitch of the lowest resonant frequency in that bunch. This is

the fundamental frequency. You can think of it as the baseline. In musical instruments. The additional resonant frequencies those higher than the fundamental frequency, higher in frequency, so more hurts. In other words, are typically, but not exclusively, harmonics of the fundamental and a harmonic is a whole number multiple of the fundamental frequency. So let's focus on that guitar string. It's a lot easier if we talk about a specific example.

So we're gonna say that we're gonna play the A string. Why the A string, Well, because it has a fundamental frequency of one ten hurts. It makes it very easy for us to do multiples. So the fundamental frequency sees the string vibrate one hundred ten times per second. That means a full sequence of going up and down and returning to starting point on times per second. The string

is anchored at either end of the guitar. If we could slow down time, we would see that length of string making that up down journey one ten times every second. But the string is also vibrating at other frequencies that are higher than the fundamental In general, we call these overtones together. The overtones with the fundamental frequency are called partials. Now I'm going to focus on harmonics first because they are the easiest to grasp. So we've got our a

string with a hundred ten hurts frequency. That's our fundamental tone or first harmonic. The next harmonic would be twice the frequency as two is the next whole number. It's the next integer in the sequence. We start with one, but any number of times one is itself. We go to the next integer, that's two. So now we multiply our frequency hurts by two, we get two hurts. That's still an A. It's still the note A, but it's an octave higher than the original a note that we played.

So hypothetically, this also means if you've got a string that's tuned to one hurts and you shortened the length of that string by half, so you made it half as long, you would produce the two D twenty Hurts tone when you strummed the half as long string. You shortened the wavelength by shortening the string. Thus you increase the frequency because remember we remember velocity is wavelength times frequency. Velocity is constant, so if we have the wavelength, we

have to double the frequency. At least that's what would happen in an ideal realization of this principle, But in reality it gets more complicated because the oscillating wave in a guitar string doesn't propagate all the way from one anchored end of the string all the way to the other end of this string. Instead, there's actually a small length of string that's close to the anchor points that doesn't move. It's something that people tend to call the

dead length of string. Now, the amount of dead length, like the length of that non moving part of the string, depends on a lot of factors, like how thick the string is, so there's no hard and fast rule of how long the dead length will be. In general, this actually means that the actual halfway mark down a string doesn't necessarily correspond to doubling the vibrational frequency of that string. But we'll get more into that in the next episode, I hope. So we're gonna put it aside for now.

That's a future Jonathan problem. So the next harmonic would be three times the fundamental right, we just did two hurts, so three would be that's right, three thirty hurts, which we would perceive as an E note if we could hear it over the fundamental frequency, and so on. We would go up the harmonic scale. The fourth harmonic at four or forty would get us back to another A note at a higher octave uh five fifty For the fifth harmonic would actually be close to a C sharp,

but not exactly C sharp. It would be a little off by just a few hurts. Now, overtones aren't necessarily at harmonic frequencies. We tend to design musical instruments that produce harmonics as overtones because we find them more pleasing to the ear. Typically, but different instruments will produce different overtones. At different intensities, So some might really emphasize the third partial or third harmonic, others m really emphasize the fifth harmonic.

And this is why we can hear the same note played on two different types of musical instruments, and we experienced two different qualities of sound, two different experiences of sound. So a G played on a banjo sounds different from that same G note played on a guitar, and that sounds different from that same G note played on a piano or a G on a trumpet. Each of these

instruments produces overtones of varying degrees of intensity. And while we don't necessarily perceive the pitch of those overtones, we don't, you know, distinguish those other pitches. The overtones shape the sound, It affects the timbre of the note. So we can tell the G on a banjo and the G on a guitar are the same pitch, they're the same note,

but they don't have the same quality of sound. If they did, there'd be no reason to make different musical instruments because they would all just produce the exact same sounds. There's something else I need to say about resonance and

it involves adding energy into a system. One way to think about this is with a swing set, So you know, and you're a kid, or if you're me an adult and you're swinging on a swing set, if someone gives you a push just as you were about to start your downward swing, you go a little higher on your next swing because that push was adding to the natural frequency of your swing. You're adding energy into the system.

So objects will resonate at certain frequencies, and if you add energy at the regular intervals of that frequency, it boosts the amplification. You get more volume, you get more energy, And it depends on a load of factors, such as what the physical stuff is made up of, how much of it there is, the tension that's on it, and lots of other stuff. But resonance is going to play

an important part in how some specific instruments work. So if a musician subjects an instrument at a resonant frequency in some way, the sound creative and the instrument will be a louder one. The classic example of resonance is using a crystal champagne glasses fundamental frequency to shatter the glass, and it's a neat trick, so The first thing you gotta do is determine what the glass is fundamental frequency is.

Typically you do that by tapping it lightly, and you would listen to the tone it produces, and you would analyze that tone. Then you would subject the glass to that same frequency of sound. The glass will begin to vibrate in the presence of that fundamental frequency all by itself, so you don't have to strike it or anything. It's as if the glass has been struck. It will resonate along with that frequency. It will also do this, by the way, if you're doing one of the harmonics of

that frequency, but at a lesser degree. So if the incoming frequency is strong enough, it will cause the glass to vibrate to the point that deforms enough to shatter. And there are a lot of stories of opera singers who had perfect pitch who could managed this. They would listen to the tone and replicate it perfectly, and with their training, they would produce in a volume loud enough

to shatter the glass. These days, it's a lot easier to do this because you just use a digital device capable of dialing into a precise frequency, and then you pump that frequency out to some speakers that can blast out the sound at a sufficient volume and the glass will just shatter itself. But uh, we're not done with the hard stuff yet. Now we have to talk about Furrier transforms. And who knew that music was so darn complicated? I mean, Bach did, but you know you get what

I mean. Back in the eighteenth and early nineteenth centuries, we had this smarty pants named Jean Baptiste Joseph Fourier, or Old Joe as i'll call him. So. Old Joe was a physicist and a mathematician born way back in seventeen sixty eight, and he was really interested in explaining the flow of heat between adjacent molecules. But his work would lay the foundation for other smarty pants assess is to build upon net, leading to what we would call

the Furrier transform. Not many people called the Furrier transform, so I'll just say Furrier. But what the heck does this have to do with music? Well, remember when I said if you wanted to depict a true sound wave as a type of sign wave, it would look really funky because the presence of all those overtones, it would make all these different dips and peaks, and it would

just look very odd. It wouldn't be those smooth curves we were talking about originally, Well, we humans wouldn't hear all those frequencies as distinct pitches, but a meter could

pick up all those different frequencies together. Basically, the Furrier transform describes how these multiple frequencies all combine into that one wave, which in our sketch means it creates that single wave visualization that incorporates all the frequencies at their respective amplitudes into a single, unbroken visualization of a wave. Furier showed that a continuous function could be produced as

an infinite sum of sign and cost sign waves. The resulting plot of the function as a wave isn't necessarily smooth, and the shape of it will depend upon a lot of factors, including the phase of each constituent wave, the frequency, the amplitude, all that kind of stuff. But Furry and those who followed him described how this collection of individual

components combine to make a whole. This applies in lots of areas of physics, not just in sound, and in fact we can visualize sound waves in a different way. There's more helpful when we try to understand this. So we've used the time domain method. Right, we've been using that in order to describe the the wavelength and frequency because those are really easy to visualize in terms of of span of time. However, it gets confusing when we want to talk about overtones and the shape of the

wave goes all funky. So we can do this by looking at it not by the time domain but by the frequency domain. So in the time domain, that horizontal line or x axis relates to the passing of time, but in the frequency domain, the x axis refers to the range of frequencies, lower frequencies being on the left side, higher frequencies being on the right side. So you would plot where the frequency is on each of those overtones, and the fundamental frequency uh and the y axis is

still amplitude, so it's still volume. So you would have the loudest frequency, which would be the fundamental, plotted at the highest point on the y axis, and then you would see the overtone frequencies at their respective places, and you would see, if you were to analyze through Furrier analysis each musical instrument, that those overtones are slightly different between things like guitars and banjos and harps and pianos

and flutes and trumpets, etcetera. Uh, and other things like like whether or not you were plucking a string versus bowing a string. All of these factor into it. Now I get that all of this is really confusing without visual aids, So I do recommend checking this stuff out on the internet to get a better grasp of it. There are numerous websites and videos on the matter, and one really helpful one relating to what I was just

talking about is on Mark Newman's YouTube channel. It's titled Preview how the Furrier transform works Lecture number two Sound as sign Waves. Check that out. It will really help clear things up. But when we get back, I'm gonna wrap up the physics bit. Then we're gonna talk about

some biology. But first let's take a quick break. So Furrier analysis, where we can determine the amplitudes of individual overtones and harmonics and a played note, gives us the scientific explanation of why the same note played across different instruments produces a different kind of sound. The collection of those overtones is different for every instrument. But how about how we actually hear and perceive sound? What is the

science behind our experience of sound? Well, we'll start with the physics and those moving air molecules what go into our ears. So we're really talking, like I said about fluctuating air pressure. Here, those changes in air pressure hit our ears and they pass into the external auditory canal, so that's open to the outside world on the inside in our heads. It ends with the tympanic membrane, also known as the ear drum. So this is a very thin membrane and it's at where we would say the

outer ear begins to transition to the middle ear. On the other side, the inner side of the tympanic membrane is a series of three tiny bones. There, the malleus, the incas, and the statepies or the hammer, the anvil and the stirrup, so called because of their shape, and as the membrane moves due to these fluctuations of air pressure, as it's being pushed and pulled upon, the bones also move, So the hammer pushes impoles on the anvil, which pushes

impolls on the stirrup. The stapes or stirrup connects to the oval window. That's a section that's part of the cochlea that's an organ in the inner ear. The cochlea is a spiral shaped organ and there are three parallel chambers filled with fluid inside the cochlea. The vibrations on the oval window cause waves to flow through this fluid. This in turn causes another membrane called the basilar membrane

to move. And it's the basilar membrane or basil or if you prefer, that gives us the ability to differentiate the pitches that we hear. Different sections of this membrane respond more readily to certain frequencies of sound. Then you have the organ of core time, which is the receptor organ of the ear, and it detects the vibrations of this basilar membrane through special cells, and the special cells

have little hair like protrusions on them. It acts kind of like a brush that just rests against this membrane. So as the membrane vibrates, the hair cells pick it up, and then they pass along the message to the brain through neurotransmitters, and it gets super complicated from there. But I figured this is deep enough already. At the end, our brains taken these incoming signals and then interpret it

and we experience it as sound. Now you can also transmit vibrations to the tympanic membrane through stuff like bone conduction. That's where the vibration passes, not through air molecules that are going through the ear canal, but rather through the bones of the skull itself. So just remember that again, sound is one way we experience vibration, but not the only way. I mean, obviously, if a vibration is strong enough,

we're gonna feel it. And some vibrations occurrent frequencies that again are too high or too low for us to perceive through sound through hearing it, but we might be able to feel it. So the basilar membrane won't vibrate at frequencies that are above or below the human range of hearing, or an individual's range of human hearing, because when we say twenty to twenty killer hurts, we're really talking about the range of the typical human. Some people

are atypical. So you could say if a tree falls and the vibrations that cause were above or below the level of perception, it doesn't make a sound because sound is dependent upon us experiencing it. You could also argue the opposite. It all just depends on your way you're defining things. So when a musician strums a string on a guitar, that string vibrates, it causes the air molecules around the string to move. Thus you get a fluctuation

of air pressure that matches that vibrating frequency. This spreads outward from the source and the air molecules all around vibrate, and if you're close enough, if you're within hearing distance, that fluctuation will be strong enough to move your tympanic membrane, which then is going to through the bones put pressure on that oval window of your cochlea, which in turn will cause the basilar membrane to vibrate at the particular

area on the membrane that corresponds to that frequency. The hair cells will pick up that vibration and then emit neurotransmitters that our brains then say, oh, I recognize that that's in agata da vida boom. We've just heard some music. So when you get down to it, musical instruments are all about creating vibrations at specific frequencies. Music itself is all about establishing rules which can occasionally be broken for the arrangement of those frequencies in ways to achieve various effects.

Those rules aren't just about which frequencies play well with others. It's also about stuff like amplitude. Levels of volume are really important and play into a song's dynamic range. Dynamic range explains the difference between the loudest versus the softest parts of a piece of music, and the limitations of

human hearing also play an important part. So, for example, it's very hard for humans to pick up on a soft sound that immediately follows a loud sound, much like we really only hear the fundamental frequency played on a musical instrument. So if you wrote a piece of music that has a really loud moment followed immediately by a very soft one, chances are no one would ever hear the soft part. This also plays a big part in

strategies that revolve around audio compression. If you've listened to my episodes about the MP three format, you know that some forms of compression rely on what's called a lossy formula. As the name implies, lossy compression is able to reduce file size by ditching some of that data, you lose some of the information. The goal of lossy compression is to get rid of data without perceivably changing the quality of the sound file or reducing any perceivable quality as

much as possible. The first way to do that is to identify any sounds that theoretically should be imperceptible to the average person and then just getting rid of them, because if you can't hear it, why would you keep it. But as we've learned, stuff like overtones are also important. They are what characterized the quality of a particular musical instrument, even though we don't directly perceive the pitches underneath those

overtones as distinct notes. So lossy formats have to take that into account, or the compressed file is just gonna

sound weird. Guitars won't sound like guitars, for example. So interestingly, there's a lot of psychology that goes into audio compression by combining our understanding of physics, even if it was a limited understanding or perhaps more of an observation without full understanding, with our appreciation for which frequencies are pleasing to us, and the limitations that we have as human beings.

We can construct various instruments to play into all of this, but it all comes down to how can I construct something that will vibrate and make those vibrations sound good. I'd love to give you history of musical instruments, but humanities relationship with music dates back before our relationship with written language. Among the oldest instruments ever discovered where flutes from European caves. These flutes were made out of bird bone and mammoth ivory and they were built more than

forty thousand years ago. And keep in mind I said these were the earliest ones that we've discovered. Who knows when humans first made musical instruments. If I had to guess, I would wager that percussion instruments like drums were among the earliest. But there are a lot of other ancient examples, and one I want to talk about is particularly interesting. I want to close out with this ancient musical instrument because there are people who still use it today and

it's super cool. It's called the bull roarer. It's hard for me to say that word, being Southern bull roarer. I just want to make it a two syllable word. But these were used as far back as the Stone Age. Typically these consist of a slat of wood, and it's usually shaped so that there's an edge on either side of the slat of wood. So think of like a ruler, but you've you've shaved the edges of the ruler down so that it's kind of like the propeller on an

old prop plane. And you wrap a chord around one end, or you may drill a hole, loop the cord through the hole and tie it off, and then you give the cord a little bit of a twist, and then you hold the other end of the cord and you start swinging the bull roarer in a circle. As it swings, the cord begins to untwist, and then it continues twist

in the opposite direction before reversing the process. So the bull roarer moves along the path of the circle, and as it's doing so, it's turning because of the cord twisting and untwisting, And this movement through the air creates the vibrations that travel as sound. Several factors can influence the pitch of that sound. That includes the length of cord ear using, which obviously determines the diameter of the

circular path that the bull roarer is taking. Also the frequency with which you are swinging this in a circle, the amount of twists that was in the cord, and even the plane of rotation, whether it's vertical versus horizontal. For example, bull roarers were used by many ancient peoples as a means of communication by varying the pitch, which again you could do in all those different ways I just mentioned. You could send simple messages several miles away

because the sound would just travel so far. Those low frequencies travel pretty well. The fact that you're talking about longer wavelengths um and and lower frequencies, the energy is much more efficient at far distance travel, and so these were used by early civilizations for thousands of years as a way for people to send distant messages back and forth. Pretty simple messages, but distant ones that could be very

helpful for early civilizations. In the next episode, I'm going to go into more detail about how specific types of musical instruments actually work, how they create the sounds they make. I'm going to focus on the musical instruments found in Western orchestras, because to cover all musical instruments would require its own podcast series, and if I were to cover how bagpipes works, I would probably need a therapist. But I hope you guys enjoyed this overview of the science

of producing sounds. If any of you out there have any suggestions for future topics I should cover, whether it's a specific technology, a type of tech like I'm doing now, a company in technology, or a very important person in tech, or anything along those lines. Let me know. You can reach out on Facebook or Twitter. The handover both is Tech Stuff HSW and I'll talk to you again really soon. Y tex Stuff is an I heart Rate deo production.

For more podcasts from I heart Radio, visit the I heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows. H