Gadgetory

we hear about decibels all the time when shopping for I don't know a Bluetooth speaker wireless antenna or whatever else but many people I talked to are shocked to hear that when one thing is rated at twice as many decibels as something else that does not mean it's twice as strong or twice as loud let's start at the beginning shall we the base unit in this case is actually the bell named in honor of Alexander Graham Bell who achieved fame and fortune most notably for filing a patent for the work of Antonio Meucci the true inventor of the telephone anyway that's a whole other discussion call me we'll talk about it sometime the point is one Bell represents a difference in a relative power of 10 with a decibel being 1/10 of a Bell so if one value is 10 decibels higher than another it is an order of magnitude greater whereas a 20 decibel difference will be two orders of magnitude greater and so on and so forth well hold on a second Linus if it's a unit of relative rather than absolute measure then how can we possibly say something like this as a three decibel antenna or this fan is rated at 21 decibels you see that next to the decibel symbol for that fan that is how it's all about context decibels have been adapted for many different uses so they can be expressed more easily by defining standard reference points or a base value in the case of an antennas gain reputable companies will rate them in DB D or relative to a dipole while companies who want to show inflated numbers will rate in DB I relative to an imaginary antenna that radiates in all directions and then in the case of noise the main focus of this video we use sound pressure level a measurement in decibels above a base value approximately equal to the threshold of human hearing okay cool Lynas odd now I know what a decibel is but logarithmic units are a little hard to compare in your head when you're shopping for a cooling fan or air conditioner or something so one buddy told me that I can just kind of go well a three decibel gain is an effective doubling of sound well I heard from someone else that it's six decibels which is right aha this is where things get really fun three decibels equates approximately to a doubling of the power ratio but when we want an amplitude ratio let's say to express relative voltage or a field quantity like sound pressure level we need to square the amplitude which means that a difference of 6 decibels will equate to double the voltage or double the sound pressure level if you measure it but that doesn't mean to your ears a vacuum cleaner rated at 6 decibels lower than another will actually sound half as loud as the next leading brand or whatever your ears don't hear increases in sound pressure in a linear fashion in fact depending on the frequency of the noise the general rule of thumb is that it takes somewhere between a 6 to 10 decibel increase in sound pressure to achieve a perceived doubling of loudness alright Linus I get it now but why do we need a unit of measurement that appears to have been designed to confuse people and make comparisons difficult fair question there is the bit about how human perception of sound and also light actually is more closely related to the logarithm of intensity rather than the intensity itself but the main reason is that it allows the use of much smaller numbers in cases where we need to compare values that can differ by many orders of magnitude instead of saying these speakers don't end billion times louder than to beat human hearing threshold we just say it's a hundred decibels SPL but if you're sitting there worried about how you're ever going to remember all of this fear not wikipedia has a handy dandy chart that you can reference next time you see a loudness rating in decibels so that you have some context for interpreting the otherwise truthfully pretty confusing numbers speaking of confusing today's episode sponsor is Linda comm an amazing way to increase your understanding of a variety of 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something to say that's more complicated than this thanks again for watching and as always don't forget to subscribe and share please share when you share I get a lot more subscribers and then my ego is like bah then I get huge like this and have no neck like this so could you die without a neck