Alan takes a deeper dive into decibels

Many thanks to SWLing Post contributor, Alan Fahrner, who writes:

One of your articles below inspired me to write this:

https://math.promo/2019/12/shortwave-decibels/

This past August I went back for a second bachelors, this time in mathematics. So, I love when real life can be used as an example of answering the age-old question, “When am I ever going to use this?” about math. 🙂

Happy New Year!

And a Happy New Year to you, too, Alan! Thanks for sharing!

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4 thoughts on “Alan takes a deeper dive into decibels

  1. mangosman

    This article has a fundamental flaw
    0 dB equals no change ie the power 1 and power 2 are equal It is a ratio, not an absolute level
    0 dBm = the reference power of 1 milliWatt and this is an absolute level as is
    0 dBW = the reference power of 1 Watt
    3 dBW is close to 2 Watts
    0 dB20 micropascal is the acoustic power the average person can hear at 1 kHz. This is another reference

    For absolute power levels the reference must be stated otherwise the dB refers to a ratio of powers.
    This is the difference between a mathematician and an electronics engineer!

    Reply
    1. RonF

      I agree it’s more clickbait-y title than actual article, but:

      “This article has a fundamental flaw
      0 dB equals no change ie the power 1 and power 2 are equal It is a ratio, not an absolute level”

      Uh, Alan, it /does/ mentions that. Twice. Albeit in a quote from elsewhere. It also talks about the need for a reference level, although it doesn’t

      Personally, I have more of an issue with (a) the fact it flips between 10log and 20log without explanation, and (b) the statement:
      “If you do not see a base with your log (e.g. log10^n), then it is the “common log,” which is base 10”.

      That’s very field-dependent; for example, in anything beyond high-school statistics & maths fields the default assumption is usually the /natural/ log (i.e. base /e/), and most software (e.g. R, Octave, Matlab, ) follows that convention by default unless told otherwise.

      Reply

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