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DanielLC comments on Thinking Bayesianically, with Lojban - Less Wrong Discussion

11 Post author: DataPacRat 24 January 2012 06:47PM

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Comment author: DanielLC 25 January 2012 01:47:43AM *  3 points [-]

some people (engineers near me) use log10(x)*20 for some reason.

The power of sound goes up with the square of the amplitude, so if something has a 10 decibel increase in amplitude, it has a 20 decibel increase in power. As such, I can see how someone might get it mixed up.

A decibel is defined as 10log10(x/y), where y is whatever you're comparing it to. It should never mean 20log10(x/y).

Comment author: [deleted] 25 January 2012 06:08:26AM 0 points [-]

Well thanks for clearing that up. I would have loved to have that explained when we were all trying to figure out who decided that 20 was a good idea.

Do you know with sound what the baseline 0 db is?

Comment author: DanielLC 25 January 2012 06:36:57AM 0 points [-]

It's supposed to be on the edge of human hearing. It's also a round number. I don't remember beyond that.

Comment author: [deleted] 25 January 2012 07:15:03PM 0 points [-]

round number

measured in what? Power density or something?

Comment author: DanielLC 26 January 2012 12:36:35AM 0 points [-]

It's 20 µPa RMS, so measured in pressure.

Comment author: [deleted] 26 January 2012 02:26:41AM 0 points [-]

neat, thanks!