2. Sound Pressure - Loudness and Level

In this video, we'll look at pressure from the lens of loudness. We start with pressure, since we our ears are receptive to changes in air pressure, and is quite easy to measure. We'll look at the SI unit of pressure, Pascal, and the vast range of sound values that it can represent, all the way from the quietest (threshold of hearing) to the loudest (threshold of pain) sound that a human ear is capable of hearing. We'll also discuss pressure values of sounds higher than that, when sound morphs into shock waves at the fringe of the atmospheric pressure. But more importantly, the video sets up the discussion to talk about how to represent such a vast range of values. When a linear scale fails to give us appropriate resolution, we turn towards a logarithmic scale.
Find the full playlist here: • Loudness and Level
In this module on Loudness and Level we'll delve into how our sense of loudness is different for different frequencies and all the nuances associated with hearing. We'll look at level, and the technical ways of measuring and calculating the amplitude of signals. And finally we’ll look at a new way of measuring loudness that’s all the rage at the moment, the Loudness unit. It has redefined the standard used in streaming and broadcast, and promises to bring an end to the age of super compressed audio and the so-called loudness war.
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[@akashmurthy]

Corrections: 3:17 In an inverse relationship, the pressure would drop hyperbolically. Here's a graph of what it should look like: www.desmos.com/calculator/t2meefqsnv

[@snoozieboi]

Seriously some BBC level of educational visualization and voiceover. Some minutes later: The level of clarity in these presentations are on such a high level. This requires so much skill AND actually understanding what other people struggle to understand. My biggest frustration as a weaker student was that most of the smarter students were unable to explain what they just did or why they did it during a mathematical solution. Bridging your understanding and communicating with the clarity in this series is some impressive work. Anybody trying to write an ad, web page or any message or presentation restricted in size/time will eventually run into how what to leave out, what to keep and how does that affect the end message? Very few actually master the art of losing seemingly nothing due to the careful buildup and awareness of the listener's level of understanding. I am mightily impressed.

[@Riley-Thurm]

How one guy can know so much and produce these videos so well is amazing! Very informative

[@akashmurthy]

Thanks mate! I didn't know as much before I started making the video. So research for the video helps me out as well.

[@Riley-Thurm]

@@akashmurthy What program do you use to make the animations?

[@akashmurthy]

@@Riley-Thurm Adobe After Effects mostly..

[@lorigetz4489]

You are a genius instructor. Your approach is practically narrative and your visual implements are so accurately rendered

[@akashmurthy]

You're too kind. I'm glad you enjoyed the video.

[@JustMoseyinAround]

Thank you for not giving an example for "Loud Screaming" while I got my headphones on 😅. Great video.

[@akashmurthy]

Haha! I was so tempted. Thanks!

[@snoozieboi]

Lol, I skimmed the comments and went back up and prepared for the scream actually coming as I read too fast :D

[@johnroberts7529]

What an excellent video... many thanks. I've always had a poor understanding of sound and sound volume measurement, but this lesson is a clear and detailed analysis. Great stuff! I'm now going straight onto your follow-up video. 😊

[@fangzhi_zhao]

This is really well put together content about audio basics and recording.

[@akashmurthy]

Thanks very much!

[@fangzhi_zhao]

@@akashmurthy Can’t wait to see your new content. Really awesome work!

[@learnersqueue6339]

Love your videos and explanations mate! Really helping me out in a hard project that involves sound

[@akashmurthy]

That's great to hear! Thanks!

[@Iceman1800]

Excellent explanation. Thank you

[@akashmurthy]

You're welcome! Thanks for checking it out..

[@nandaks79]

Excellent videos and explanation. Thanks very much Akash.

[@akashmurthy]

Thank you very much! :)

[@sarinsahil]

Thanks for these videos! Keep em coming :)

[@akashmurthy]

Cheers! More on their way!

[@fantastic_n0b]

Wow this is gold content

[@arbuckle2012]

This is really clearly explained. Thank you so much!

[@akashmurthy]

You're welcome! :)

[@sreekethavvaka8726]

enjoyed every second : )

[@akashmurthy]

Cheers mate!

[@michamerckx3285]

These videos are Amazing!

[@akashmurthy]

Glad you think so!

[@upendraagnihotri2686]

Wao what an explanation...such a wonderful video and so fewer views....people should get their perception level checked.

[@akashmurthy]

Haha, thanks! I wish there were more views as well!

[@upendraagnihotri2686]

Akash Murthy I will share it you deserve millions views and million subscriber ...rest assured all good things take time.

[@vivekgupta2193]

This is great Man. Cool video too. Do you make the video content yourself?

[@akashmurthy]

Thanks man! Yea I make the whole thing.

[@goofgoof3663]

I’m a bit confused: How are we able to take 101,325 pascals from everyday atmospheric pressure if 100 pascals is our threshold of pain?

[@akashmurthy]

A bit confusing indeed. Give it a another listen from 1:30. Think about how a deep sea diver has to come back to the surface slowly. If he surfaces really fast, the change in pressure could potentially kill him. He'd have to let his body slowly acclamatize to the change in pressure. Similarly, if you've been on an aircraft, and when they take off, if they don't pressurise the cabin in time, you'll feel your ears pop! All of this tell us one thing. The human ear is very sensitive to CHANGES in pressure. It doesn't matter too much what the pressure of the medium is. If you're swimming around in water for example, the pressure exerted against your ear is much higher. All that matters is we are acclamatized to a constant pressure. Now, for the other part, 100 Pascal as the threshold of pain. When you experience sound, it's the oscillation of pressure. If pressure of the medium oscillates back and forth at around 440 times a second, we get the perception of a 440Hz tone. Now think about a pressure change of 100 Pa happening many many times a second. The pressure would go from 101,225 to 101,425 several times a second for us it to be able to hear it! This is the problem! The change in pressure is too massive. If this didn't happen, several times a second, and if it happened slowly, it wouldn't affect us as much, but also, we'd never be able to hear it, so it wouldn't be audible sound at all. Hope that helps

[@goofgoof3663]

@@akashmurthy So to clarify, humans can hear as low as 20 micro pascals given no atmospheric pressure? Or is it that humans can hear as low as a 20 micro pascal shift of pressure from the constant atmospheric pressure (such as from 101,325 pa to 101,325 pa + 20 micro pa)?

[@akashmurthy]

@@goofgoof3663 The second one is bang on right!

[@goofgoof3663]

@@akashmurthy What about a 20 micro pascal reduction from the 101,325 atmospheric pressure? or similarly 2 milli reduction? what does that do and what would we register it as? For example, could it hurt a human if it immediately switched from outdoor environment to an anechoic chamber?

[@akashmurthy]

Think about the eardrum as a physical drum. If you hit the drum really really hard, it's bound to rupture. We can think about this as the threshold of pain. The threshold of hearing can be just touching the drum head softly, or not hitting it at all. Your question can translate to: what happens when the drum is hit hard and immediately not hit at all. So, nothing happens, the drum head is fine. That's because, the drum head doesn't stop resonating immediately. The momentum of resonation will continue and it'll ring for a while before it stops. Same thing happens to our ear, it'll continue to ring for a while before it becomes totally silent. This is not to be confused with Tinnitus, where the ear is damaged due to loud sounds and the ringing stays for many days.

[@jjlopez5764]

Brilliant 👏🏽👏🏽👏🏽 thank you

[@akashmurthy]

Thanks for checking it out!

[@martinsanchez-hw4fi]

Still don't get why pressure follows inverse distance, but intensity follows inverse square distance law. Both of them have area as denominator

[@akashmurthy]

But their numerator isn't the same, pressure is N/m2, while intensity is W/m2. In any case, the reason why the pressure is inversely proportional to distance, and intensity is inversely proportional to square of the distance is because intensity is proportional to square of the pressure. I've explained this in a later video in the series I think.

[@lolololxd456]

thank you for the video!! but i dont understand the pressure=1/distance formula. if this formula gives us a certain pressure measured in pascal, and pascal is newton(force)/m²(distance), i'm guessing 1 is the force in this case. but why? what is this 1 force and what does it represent? im not good at physics so this question might be a bit dumb, sorry!

[@akashmurthy]

Cheers, thanks for watching! That's not the formula, pressure is NOT equal to 1/distance. Pressure is inversely proportional to the distance. The only thing that relationship says is that if distance decreases linearly, pressure increases linearly!

[@lolololxd456]

​@@akashmurthy oh i see, i took it too literally then! thank you so much! this is unrelated to my question, but i'm a 1st year sound engineering student and your channel has been incredibly helpful!! i'm beggining to understand everything my teachers have either ignored or poorly explained without any graphics or visual representations. if i pass my next exam it's thanks to you! have a nice day:)

[@alexanderczako4865]

Hello, at 3:17, as pressure is inversely proportional to the distance from the source, the relation between them is not linear but hyperbolic, is it?

[@akashmurthy]

Omg, you are totally right! I don't know what I was thinking when I wrote that. I will put up a correction in the comments. Thanks!

[@NishanthSalahudeen]

3:48 smallest audible sound is well established for 1hz sine tone? As i remember, 20hz is lowest human can go on average. After watching the 3rd video in this series i found that its 1khz and not 1hz. Its a slip of tongue.

[@akashmurthy]

Yup, I misspoke, but the text in the video describes it as 1kHz

[@NishanthSalahudeen]

@@akashmurthy was only listening. Thats a popular way of consuming youtube videos too. But i understood what you said.

[@RahulSharma-oc2qd]

To be honest, I’ve had far too less knowledge in the topic and after seeing your video, I am more confused but at the same time it made me dumbfounded. I am sorry, couldn’t suggest it to any newbie.

[@jeanking4686]

Yea well it does require a bit of familiarization with at least the concept of satp or stp at a highschool chemistry level Edit: or highschool physics really

[@BobEnyartLive]

Thanks for a great video! One minor correction. We didn't evolve. Discovery of dinosaur blood proves they're young, and collapse any timeframe for neo-Darwinism to function. Over 50 papers now published on dino still-soft biological matter (like in Egyptian mummies) from their homes and skin. bflist.rsr.org