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Acoustic weighting curves A, B, C, and D, usually used in acoustic measurements to approximate the human hearing response. (A and C are by far the most popular.)

Instructions

See Wikipedia graph-making tips.

Generated in gnuplot with the following script (after a lot of trial and error):

 
This plot was created with Gnuplot by n.

To convert the PostScript file to PNG:

  1. Open it in the GIMP (make sure you have ghostscript installed! - Windows instructions)
    • Enter 500 under Resolution (it doesn't say "DPI" but I think that's what it means)
    • Uncheck Try bounding box (since the bounding box cuts off the edge, unfortunately. You can try with the bounding box first.)
    • Enter large values for Width and Height
    • Check Color
    • Check Strong anti-aliasing for both graphics and text
  2. Crop off extra whitespace (Shift+C if you can't find it in the toolbox)
  3. Possibly need to rotate it: Click ImageTransformRotate 90 degrees clockwise
  4. FiltersBlurGaussian blur at 2.0 px (No need to blur if you use strong anti-aliasing during conversion. I see no significant difference between end results.)
  5. ImageScale Image...
    • Width and Height at 25%
    • Cubic interpolation
  6. You can view at normal size if you want by pressing 1, Ctrl+E
  7. Save as Weighting curves.png

Functions are from the weighting filter article (which in turn are from a website). Normalizing constants were determined in Maxima from something like this:

kA*s**4 / ((s+129.4)**2 * (s+676.7) * (s+4636) * (s+76655)**2);
ev(%,s=%I*2*%PI*f);
abs(%);
ev(%,f=1000);
solve(%=1,kA);
float(%);

or just

float(solve(ev(abs(ev(%,s=%I*2*%PI*f)),f=1000)=1,kA));

It might look a little better if the range of the D curve were limited, as in http://www.extron.com/technology/img/loudnesscontrol_ts_3-lg.jpg


Created by User:Omegatron using gnuplot, possibly with post-processing in the GIMP (PNG) or Inkscape (SVG)

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File history

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Date/TimeThumbnailDimensionsUserComment
current20:42, 1 July 2005Thumbnail for version as of 20:42, 1 July 20051,600 × 1,600 (212 KB)OmegatronAcoustic weighting curves A, B, C, and D, usually used in acoustic measurements to approximate the human hearing response. (A and C are by far the most popular.) Source: Created by User:Omegatron {{SelfBSA}}