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we hear about decibel all the time when

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shopping for I don't know a Bluetooth speaker a wireless antenna or whatever

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else but many people I talk to are

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shocked to hear that when one thing is rated at twice as many decb as something

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else that does not mean it's twice as

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strong or twice as loud let's start at

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the beginning shall we the base unit in this case is actually the Bell named in

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honor of Alexander grambell who achieved Fame and Fortune most notably for filing

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a patent for the work of Antonio miuchi the true inventor of the telephone

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anyway that's a whole other discussion call me we'll talk about it sometime the

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point is one Bell represents a difference in a relative power of 10

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with a decibel being on10th of a bell so

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if one value is 10 DB higher than another it is an order of magnitude

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greater whereas a 20 dcel difference would be two orders of magnitude greater

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and so on and so forth well hold on a second lus if it's a unit of relative

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rather than AB absolute measure then how can we possibly say something like this

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is a 3 D antenna or this fan is rated at

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21 DBS you see that a next to the

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decibal symbol for that fan that is how

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it's all about context decibel have been adapted for many different uses so they

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can be expressed more easily by defining standard reference points or a base

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value in the case of an antenna's gain reputable companies will rate them in

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dbd or relative to a dipole while companies who want to show inflated

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numbers will rate in DBI relative to an

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imaginary antenna that radiates in all directions and then in the case of noise

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the main focus of this video we use sound pressure level a measurement in

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decb above a base value approximately equal to the threshold of human hearing

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okay cool Linus uh now I know what a deciel is but logarithmic units are a

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little hard to compare in your head when you're shopping for a cooling fan or air

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conditioner or something so onebody told me that I can just kind of go well a 3

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dbel gain is an effective doubling of sound well I heard from someone else

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that it's 6 DB which is right ha this is

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where things get really fun three DCB equates approximately to a doubling of

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the power ratio but when we want an

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amplitude ratio let's say to express relative voltage or a field quantity

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like sound pressure level we need to square the amplitude which means that a

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difference of 6 DB will equate to double

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the voltage or double the sound pressure level if you measure it but that doesn't

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mean to your ears a vacuum cleaner rated at 6 DB lower than another will actually

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sound half as loud as the next leading brand or whatever your ears don't hear

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increases in sound pressure in a linear fashion in fact depending on the

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frequency of the noise the general rule of thumb is that it takes somewhere

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between a 6 to 10 D increase in sound

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pressure to achieve a perceived double

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of loudness all right lonus I get it now

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but why do we need a unit of measurement that appears to have been designed to

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confuse people and make comparisons difficult fair question there is the bit

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about how human perception of sound and also light actually is more closely

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related to the logarithm of intensity rather than the intensity itself but the

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main reason is that it allows the use of much smaller numbers in cases where we

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need to compare values that can differ by many orders of magnitude instead of

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saying these speakers go 10 billion

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times louder than your weak human hearing threshold we just say it's 100

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DB SPL but if you're sitting there worried about how you're ever going to

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remember all of this fear not Wikipedia has a handy dandy chart that you can

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reference next time you see a loudness rating in decb so that you have some

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context for interpreting the otherwise truthfully pretty confusing numbers

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speaking of confusing today's episode sponsor linda.com an amazing way to

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watching guys like the video if you liked it dislike it if you disliked it leave a comment letting me know if you

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have any suggestions for future fast as posses or if you have something to say

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that's more complicated than this thanks again for watching and as always don't

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forget to subscribe and share please

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share when you share I get a lot more subscribers and then my ego is like and

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then I get huge like this and I have no neck like

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this would you die without a neck