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SR1 Reference 307
© 2014 Stanford Research Systems
the poles in the A-Weighting transfer function are purely real, the imaginary part of each pole in this file
is 0. Note that the two repeated poles are simply repeated in the list. Note that the poles in the list are
given with values in Hz. Since this is an s-plane transfer function the actual poles should be given in rad/
sec. This is handled by the line:
<EQdata Name="PZmultiplier" Type="3" Value="-6.283185307"/>
This specifies that all pole and zero values should be multiplied by -2 . This converts the Hz values into
rad/sec values and also moves poles into the left hand plane, where stable poles are located.
The real and imaginary parts of zeros are specified in a similar manner by:
<EQdata Name="ZerosReal" Type="DblArray" Value="0,0,0,0"/>
<EQdata Name="ZerosImag" Type="DblArray" Value="0,0,0,0"/>
These two lines give us the 4 zeros at zero frequency specified in the transfer function.
Finally, the last line in the file:
<EQdata Name="Gain" Type="3" Value="7397235900"/>
Specifies the overall multiplier for this transfer function.
A number of EQ files are supplied with SR1. By examining these files and using the information given
above it should be possible to synthesize new EQ files corresponding to any pole-zero type transfer
function.
Sampled EQ Files
Sampled EQ files represent a real (magnitude only) frequency response by storing a list of frequencies
and responses and using spline interpolation to interpolate the values at other frequency points. The list
of y-values in the files may be either pure numbers, or dB ratios. As an example, the same A-Weighting
function that was described in pole-zero format above can be represented in sampled format with the file
below:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE EQcurve SYSTEM "EQcurve.dtd">
<EQcurve>
<MetaData>
<Source Value="C:\Program Files\Borland\CBuilder5\Projects\Audio_an\EQgen\EQgen.exe"/>
<DocType Value="EQcurve_XML"/>
<Version Value="1.0.0"/>
<Date Value="2005-05-05T15:54:12"/>
</MetaData>
<EQdata Name="Style" Type="6" Value="Freq Response"/>
<EQdata Name="Freq" Type="DblArray" Value=
"0.01,0.02,0.03,0.04,0.05,0.06,0.07,0.08,0.09,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,
1,2,3,4,5,6,7,8,9,10,20,30,40,50,60,70,80,90,100,200"/>
<EQdata Name="Resp" Type="DblArray" Value=
"0.000300775933872953,0.00302174093251185,0.00932540277740184,0.0187511398949463,
0.030636637564135,0.0444168356181221,0.0596245322111266,0.075876407055739,0.0928635700095015,
0.110342389581799,0.286838481522557,0.443881655056602,0.577159672164201,0.688018968891406,
0.778916516580281,0.852785568914054,0.91256030198955,0.960885423147423,1.00000000003858,
1.14837827316987,1.15195959556707,1.11740718036267,1.06603938913942,1.00595593739291,
0.941761216135588,0.876545831584705,0.8124486702114,0.750902168765253,0.341162925654635,
0.178593707588384,0.107123333734722,0.0707303220476656,0.0499780417068754,0.037110212737056,
0.0286105664352016,0.0227144341264837,0.01846210568194,0.00466695600216974"/>
</EQcurve>