An Audio Slide Rule
No - not a slide rule that sings!

This is something I knocked up in PostScript. You can download the PostScript code here. Feel free to modify this if you want to.

Here is a PDF version, which is much easier to print. If you print this out, you can stick it to some cardboard or balsa wood and cut it in to strips. By sliding the strips against each other you can read off the relationships between various quantities rather easily. There are separate strips for:

  • Decibels and bits.
  • Pressure in dB with respect to 20uPa (micro Pascals) with hearing exposure limits and thresholds marked.
  • Tape remnant magnetization in nW/m (nano Webers per meter) with some standard levels marked.
  • Volts R.M.S. with some interesting levels marked.
  • Another decibels and bits scale with some standard-ish full scale limits marked.

Although calculators are much more accurate, seeing things laid out in this graphical way can let you get a "feel" for things which isn't so easy with a calculator. I find it quite useful sometimes.

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