4 ms·

All of that (which was quite interesting), yet he doesn't actually say what a decibel is. It is: • 0.1 bel • +/-1 bel = +/-10 dB = factor of 10 increase/decre

All of that (which was quite interesting), yet he doesn't actually say what a decibel is. It is: • 0.1 bel • +/-1 bel = +/-10 dB = factor of 10 increase/decrease in power

GuB-42 10y ago
The bel is never used in practice. Although I am probably wrong, I always thought that "decibel" actually meant "decimal bel" because it represents a decimal logarithm and that the "bel" unit was devised as an afterthought to fit the SI prefix. Still, it is a good way to remember that 10 dB = multiply by 10, because "deci" means 10.
- jpmattia 10y ago
  > and that the "bel" unit was devised as an afterthought to fit the SI prefix. It's named after Alexander Graham Bell, in 1928 at Bell Labs. https://en.wikipedia.org/wiki/Decibel#History https://en.wikipedia.org/wiki/Decibel#History (Yes I worked there, it was part of indoctrination training... :) > because "deci" means 10. Really, it means 1/10. ("Deca" is 10.)
- ScottBurson 10y ago
  > The bel is never used in practice. Ah, but it is: https://www.hgst.com/products/hard-drives/ultrastar-he12 https://www.hgst.com/products/hard-drives/ultrastar-he12 (click the "Specifications" tab and scroll down to "Acoustics") (Hmm, this doesn't say what the reference level is. I guess it's 20μPa.)
bobbles 10y ago
So 'zero' is saying 'full power' and -10db is saying '10 times less power than full power' ?
- dest 10y ago
  yes, and -20dB is 100 times less power
cnvogel 10y ago
Compare to the --at lest now, pretty obscure-- "Neper", which I've never seen used in practice except that I own a very old analog meter with a scale in Np... https://en.wikipedia.org/wiki/Neper https://en.wikipedia.org/wiki/Neper The Np seems to have be used for amplitudes (rather than power), and value/ref = e^Np. And 0.01 Np ~ 1.01 (+1%) which is probably less useful than it seems at first glance.

All of that (which was quite interesting), yet he doesn't actually say what a decibel is. It is: • 0.1 bel • +/-1 bel = +/-10 dB = factor of 10 increase/decrease in power

GuB-42 10y ago

The bel is never used in practice. Although I am probably wrong, I always thought that "decibel" actually meant "decimal bel" because it represents a decimal logarithm and that the "bel" unit was devised as an afterthought to fit the SI prefix. Still, it is a good way to remember that 10 dB = multiply by 10, because "deci" means 10.

jpmattia 10y ago
> and that the "bel" unit was devised as an afterthought to fit the SI prefix. It's named after Alexander Graham Bell, in 1928 at Bell Labs. https://en.wikipedia.org/wiki/Decibel#History https://en.wikipedia.org/wiki/Decibel#History (Yes I worked there, it was part of indoctrination training... :) > because "deci" means 10. Really, it means 1/10. ("Deca" is 10.)
ScottBurson 10y ago
> The bel is never used in practice. Ah, but it is: https://www.hgst.com/products/hard-drives/ultrastar-he12 https://www.hgst.com/products/hard-drives/ultrastar-he12 (click the "Specifications" tab and scroll down to "Acoustics") (Hmm, this doesn't say what the reference level is. I guess it's 20μPa.)

bobbles 10y ago

So 'zero' is saying 'full power' and -10db is saying '10 times less power than full power' ?

dest 10y ago
yes, and -20dB is 100 times less power

cnvogel 10y ago

Compare to the --at lest now, pretty obscure-- "Neper", which I've never seen used in practice except that I own a very old analog meter with a scale in Np... https://en.wikipedia.org/wiki/Neper https://en.wikipedia.org/wiki/Neper The Np seems to have be used for amplitudes (rather than power), and value/ref = e^Np. And 0.01 Np ~ 1.01 (+1%) which is probably less useful than it seems at first glance.