Name: Why are adverts so loud?
Uploaded: 2026-01-12T17:10:51.000Z
Duration: 7 min 58 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

I'm going to show you two very short adverts.

Here's the volume of the nice, calm one, the second one with the shouting, the background noise, the music.

If you're measuring volume purely by decibels, then it was lower, but it definitely sounded louder.

To explain that, we need to start at the beginning.

We what does it mean for something to be loud?

The tree causes the air to move, both by pushing it out the way, but

also by the tree and the things around it vibrating.

As they deal with all the forces involved, those vibrations are transferred into the air.

The actual air itself is not travelling from the crashing tree to your ears, but

rather it's a wave caused by air molecules bumping into each other.

And if you're standing nearby, then bits of that wave get funnelled by the flappy bit of your ear, the pinna, into your ear canal.

The waves get to your eardrum and it vibrates in turn, just a tiny, tiny amount behind it.

There's the three smallest bones in the human body, the hammer, anvil and stirrup.

They amplify those vibrations through leverage and deliver those vibrations into the cochlea, shaped like a snail shell, which converts it into electrical impulses that get interpreted by the brain.

If you ask a physicist, those air movements are sound.

Ask a psychologist and they'll say that until those movements get interpreted by the brain, it's just stuff moving because sound is in your head.

If the tree falls in the forest and no one's there to listen, a physicist says there's sound, a psychologist says there isn't.

And both of them are correct because they're using the same word to mean different things, which is part of why it takes so long to answer what seems like a simple question.

It's got two important the amount of pressure for each peak, the amplitude and the time between each peak arriving.

The frequency we'll start with the amplitude.

Pressure is measured in PA and regular air at about sea level has a pressure of somewhere around 100,000 pa.

That's the weight of all the atmosphere above.

Pushing down our ears can detect a fluctuation of about 20 micropascals.

A whisper in your ear would be about 2 millipascals and a and traffic noise about 200 millipascals and someone screaming at the top of their voice directly into your ear is around 20 pa, which is well into the sorts of pressure that can cause hearing loss.

Ok, as you might have noticed, that's not a particularly useful graph because the differences in scale are enormous, even if we get rid of the ambient pressure at the top.

So instead let's use a logarithmic scale, which means that each block going vertically is 10 times the previous one.

Just remember this is a 10 times jump in pressure.

The minimum that humans can detect 20 micropascals is taken as 0bels.

And then each 10 times increase in pressure adds 2bels, and we generally use 10ths of those.

So each 10 times increase is another 20db.

And I know a load of sound engineers and techies are already in the comments going no, no, no, each 10 times increases is 10 decibels, you fool.

And here's reason too why this is so difficult to There are multiple decibel scales because sound engineers talk about intensity, the amount of power transmitted, not the amount of actual pressure on your eardrum.

And look, it doesn't matter for this, just blame mathematicians, ok?

The important thing is your brain doesn't interpret ten times more change in pressure to mean ten times as loud.

Sure, traffic noise feels louder than a whisper, but

I don't think many people would guess that the amplitude is 100 times greater.

A logarithmic scale matches how we think about sound.

That's amplitude dealt with next is frequency.

It's just the number of peaks per second or hertz.

The human ear can detect roughly from 20 hertz through to 20,000 hertz.

Although that starts to decrease as people get older, the sound wave is going to be much more complex.

Of course it's usually not transmitting just a single frequency, but

let's not get into the maths of that too much.

We're particularly sensitive to the range between 2,000 and 5,000 Hertz, which means our brains perceive those frequencies as being louder.

In 1933, Harvey Fletcher and Wilderness Munson published this, which became known as the Fletcher Munson curve.

They played different sounds at different levels and noted how their test subjects perceived perceived that sound.

The curve has been updated and refined over time, and now it's usually called the equal loudness contour.

So if you want this tone and this tone to feel as loud as each other, you need to play the low one.

I want to say louder, but that's not right.

You need to play the low one with greater amplitude.

And of course, science has a measuring system for this too.

Audio engineers and broadcast companies came up with loudness units, full scale.

The calculations for this take the loudness contour into account, along with how long the loud sounds last.

LUFs are a scientific way to measure how loud something should feel, not how much the air happens to be moving.

If you're making a video for YouTube or Netflix, or music for Spotify or itunes, there are guides for you to follow.

If you upload something that's louder than that, they'll just turn the player's volume setting down automatically in the background, so people don't suddenly get startled if one video or music track is louder than another.

So that means if you're making a movie or a TV show and you want your loud sounds to have impact, you can't turn them up above the limit.

You have to turn the dialogue and speech and all the other sounds down.

That'll also cause problems, but enough that when the big explosion happens, it's noticeable, it's audible.

But advertisers don't need or want the nuance, they just want to be heard.

They usually want to be as loud as they can be throughout.

The European Union specifies -23 lufs as its target for broadcasters to try and keep adverts and programmes at the same loudness.

says that broadcasters should try to match the two, although that rule is rarely, if ever, enforced.

All of which is to say that the whisper of that first advert, the sound waves had higher amplitude.

Your eardrum will have vibrated further back and forth, but it didn't feel as loud.

There were more decibels, but fewer lufs.

And these days, it's the lufs that matter.

Seriously, this NORDVPN advert has lower sound pressure than this one does.

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