File:H&D curve.pngDescriptionH&D curve.png page 10 from Raymond Davis and F. M. Walters, Jr., Scientific Papers of the Bureau of Standards, No. 439 (Part of Vol. 18) "Sensitometry
File:Acoustic weighting curves.svg6^2)*(f^2 + 12200^2); 0.06 + 20*Log[10, num/den] ]; d[f_] := Module[ {a, h, b}, a = f/(6.8966888496476*10^-5); h = ((1037918.48 - f^2)^2 + (1080768.16* f^2))/((9837328
File:Lévy's C curve (3D-goggles).jpgLévy's C curve, a fractal. Here it's twisted into three dimensions and also over-scaled, (normally 1 / s q r t ( 2 ) {\displaystyle 1/sqrt(2)} , here
File:Circle2cardioid.png Cardioid ∂ H 1 {\displaystyle \partial H_{1}\,} is an image of circle ∂ D 1 2 {\displaystyle \partial D_{\frac {1}{2}}\,} under complex map g 1 {\displaystyle