No. Louder is not higher. The volume knob changes only the amplitude, the maximum displacement of the vibration, and that is what you hear as loudness. Pitch depends on the frequency: how many vibrations fit into a second. In an oscillogram you see loudness in the height of the wave and pitch in the distance between two peaks.
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You turn your music up. It comes out louder, and the pitch goes up with it. Is that right, yes or no? Almost everyone chooses the same here, and most choose wrongly.
In six minutes you put a vibration on a screen and learn to measure on it. You see what an oscillogram is: horizontally the time, vertically the displacement. Then come the two quantities you need again and again with sound. The period T is how long one whole vibration lasts, the frequency f is how many vibrations fit into one second, and they are each other's inverse. That is exactly what f = 1 / T says. There is a worked example in it, with the step where it almost always goes wrong: convert milliseconds to seconds first, or you end up at 0.5 Hz where 500 Hz should stand.
Then the difference the title is about. Higher you see in how closely the peaks sit together, louder in how far the wave comes from the rest position. You hear it too: two tones that differ only in frequency, and two that differ only in amplitude. Finally the difference between a pure and a complex tone, and why a spoken word looks messy on the screen and a whistled tone does not.
For upper secondary physics, on the topic of sound. The video asks a question twice and then leaves a short silence: think for yourself there first, because the answer only comes afterwards.
In this video
The full explanation, in writing
The problem
0:00You turn your music up. It comes out louder, and the pitch goes up with it. Is that right, yes or no? Almost everyone chooses the same. And most choose wrongly.
The vibration on a screen
0:14All that makes sound vibrates, and that vibration travels through the air to your ear. But what such a vibration looks like, you cannot see anywhere. There is an instrument for that, and we are going to put it on a screen now. The microphone picks it up and turn it into an electrical signal.
0:33On the screen a graph then appears: horizontally the time, vertically the displacement. How far the air particle is from its rest position at that moment. Such a displacement-time graph we call an oscillogram.
Period and frequency
0:49From that picture you can read two things, and you need those two again and again with sound. The first is how long one vibration lasts. One vibration is the whole round: from the rest position up, back, down, and back again. That duration we call the period, and we write it as a capital T, in seconds.
1:10The second: how many vibrations fit into one second. That is the frequency, small letter f, and we express it in hertz. And those two are each other's inverse: the shorter one vibration lasts, the more fit into a second. That is exactly what the formula says.
1:31f is one divided by T. Have a look at this wave. How many whole vibrations do you see here, and how long do they last together?
Six vibrations in twelve milliseconds
1:43Six whole vibrations, and together they last twelve milliseconds. Then one lasts twelve divided by six, which is two milliseconds. And now the step where it usually goes wrong: those two milliseconds must become seconds before you put them into the formula.
2:00Two milliseconds is zero point zero zero two seconds. Then f is one divided by zero point zero zero two. Five hundred hertz. Five hundred vibrations per second. If you get zero point five, you have left the milliseconds standing and not converted them to seconds.
What sounding higher is
2:22Now back to the question from the start. Two sounds, both equally far from the rest position, but one has many more vibrations in the same time than the other. That is pitch. The higher the frequency of a sound vibration, the higher the tone you hear.
2:40See what you notice it by: not by how high the wave is, but by how closely the peaks sit together. Closer together is higher.
What sounding louder is
2:56And the other. Two sounds with exactly as many vibrations in the same time, but one swings out much further than the other. That maximum displacement we call the amplitude. The greater the amplitude, the louder the tone sounds. So there sat the mistake at the start.
3:16Your volume knob changes the amplitude, and nothing else. The peaks stay exactly as far apart, so the tone stays equally high. Louder is not higher. Here are two waves. Which sounds higher, and which sounds louder?
Pure and complex tones
3:41Everything you saw until now was one neat wave: one frequency, and that we call a pure tone. But almost nothing in real life sounds like that. Say one word and there are dozens of frequencies in it at once. Together they form a complex tone, and you find it by adding up the displacements of the pure tones.
4:04That is why a spoken word looks messy on the screen, and a whistled tone does not. Three things, and with them go forward with everything that comes after. One: an oscillogram puts the vibration on a screen, with the time horizontally and the displacement vertically.
4:23Two: the period is how long one vibration lasts, the frequency how many fit into a second, and f is one divided by T. Always convert milliseconds to seconds first. Three: closer together is higher, further from the rest position is louder. Those are two different things, and your volume knob changes only one of them.
4:47Two questions, and they are not to test you but because you remember it better if you try it yourself first. First question: a vibration lasts four milliseconds. What is the frequency? Second question: someone says that a higher tone arrives at your ear sooner than a low tone. Is that right?
5:07Four milliseconds is zero point zero zero four seconds. One divided by zero point zero zero four is two hundred and fifty hertz. And the second: no. Pitch says something about how often something vibrates, and nothing about how fast it is with you.
5:28High and low arrive equally fast, because they travel through the same air. You can now read a vibration off a screen and calculate the frequency from it. And you know that louder and higher are two different things. As soon as you look at why two instruments that play the same tone still sound different, this is exactly what you need.
Frequently asked questions
What is the difference between frequency and amplitude?
Frequency is how many vibrations fit into one second, and it sets the pitch. Amplitude is the maximum displacement from the rest position, and it sets the loudness. In an oscillogram you see the first in how closely the peaks sit together and the second in how high the wave is.
How do you work out the frequency if you know the period?
With f = 1 / T. If one vibration lasts two milliseconds, first convert to seconds: 0.002 s. One divided by 0.002 is 500 hertz. Leaving the milliseconds standing gives 0.5, and that is the mistake almost everyone makes once.
What is an oscillogram?
A displacement-time graph of a vibration, with the time horizontally and the displacement vertically. A microphone turns the vibration into an electrical signal and the screen draws it, so you can read the period and the amplitude straight off it.
Does a high tone arrive at your ear sooner than a low tone?
No. Pitch says something about how often something vibrates, and nothing about how fast it reaches you. High and low arrive equally fast, because they travel through the same air.
What is the difference between a pure and a complex tone?
A pure tone has one frequency and one neat wave. A complex tone is dozens of frequencies at once, added together into one jagged wave. That is why a spoken word looks messy on a screen and a whistled tone does not.
Next time: why do two instruments playing the same tone still sound different?
Physics with Thomas makes physics explainers for secondary school. There are no words on screen, so what you see works in any language.
In this series
Sound and vibrationwhat you hear is not the air from his mouth6:53
Frequency, amplitude and pitchlouder is not higher5:57
About me
My name is Thomas Schuurmans, and I have a passion for physics and for understanding why things work the way they do. What I want is to get young people asking “why is that?” and “how does that work?” more often, and to hand them the tools of physics in a way that is simple and that you can see.
I graduated in applied physics at Delft University of Technology in 2003. After that I spent more than twenty years outside education: first at TNO, the Dutch applied research institute, then at a design agency, and eventually founding Proportion Global, through which I work on innovation questions in Africa, Latin America and South Asia. That work resembles physics more than you would expect: don't start from a solution, first understand what is going on, try something, be wrong, and look again.
Since 2026 I have been teaching physics to both lower and upper secondary classes, and I started a master's at the University of Amsterdam for my full teaching qualification. That is where I learned that a secondary school pupil's real attention for new material lasts about seven minutes. And my own weakness happens to be telling too many side stories.
That is where the idea came from: videos that explain one topic sharply and visually, inside those seven minutes. I make them for my own pupils. Then I publish them, because good explanation should be within reach of anyone who needs it, wherever you live and whatever language you think and speak in.