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Impulse response acoustic information calculator

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Impulse response acoustic information calculator

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10 Jul 2013 (Updated )

Calculate RT, DRR, Cte, and EDT for impulse response file

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Description

Calculate RT, DRR, Cte, and EDT for impulse response file
  RT = IR_STATS(FILENAME) returns the reverberation time (to -60 dB)
  using a method based on ISO 3382-1:2009. The function uses reverse
  cumulative trapezoidal integration to estimate the decay curve, and a
  linear least-square fit to estimate the slope between 0 dB and -60 dB.
  Estimates are taken in octave bands and the overall figure is an
  average of the 500 Hz and 1 kHz bands.

  FILENAME should be the full path to an audio file or the name of an
  audio file on the Matlab search path. The file can be of any format
  supported by the AUDIOREAD function, and have any number of channels;
  estimates (and plots) will be returned for each channel.

  The function returns a 1xN vector of RTs, where N is the number of
  channels in the audio file.

  The function determines the direct sound as the peak of the squared
  impulse response.

  [RT,DRR] = IR_STATS(FILENAME) returns the direct-to-reverberant-ratio
  DRR for the impulse; DRR is the same size as RT. This is calculated
  in the following way:
  
  DRR = 10 * log10( X(T0-C:T0+C)^2 / X(T0+C+1:end)^2 )

  where X is the approximated integral of the impulse, T0 is the time of
  the direct impulse, and C=2.5ms [1].

  [RT,DRR,CTE] = IR_STATS(FILENAME) returns the early-to-late index CTE
  for the impulse; CTE is the same size as RT. This is calculated in
  the following way:
  
  CTE = 10 * log10( X(T0-C:T0+TE)^2 / X(T0+TE+1:end)^2 )

  where TE is 50 ms.

  [RT,DRR,CTE,CFS] = IR_STATS(FILENAME) returns the octave-band centre
  frequencies CFS used in the calculation of RT.

  [RT,DRR,CTE,CFS,EDT] = IR_STATS(FILENAME) returns the early decay
  time EDT, which is the same size as RT. The slope of the decay curve
  is determined from the fit between 0 and -10 dB. The decay time is
  calculated from the slope as the time required for a 60 dB decay.

  ... = IR_STATS(...,'PARAMETER',VALUE) allows numerous
  parameters to be specified. These parameters are:

      'graph' : {false} | true
          Controls whether decay curves are plotted. Specifically, graphs
          are plotted of the impulse response, decay curves, and linear
          least-square fit for each octave band and channel of the audio
          file. If the EDT output is specified, the EDT fit will also be
          plotted.
      'te' : {0.05} | scalar
          Specifies the early time limit (in seconds).
      'spec' : {'mean'} | 'full'
          Determines the nature of RT and EDT outputs. With spec='mean'
          (default) the reported RT and EDT are the mean of the 500 Hz
          and 1 kHz bands. With spec='full', the function returns the
          RT and EDT as calculated for each octave band returned in
          CFS; RT and EDT have size [M N] where M=length(CFS).
      'y_fit' : {[0 60]} | two-element vector
          Specifies the decibel range over which the decay curve should
          be evaluated. For example, 'y_fit' may be [-5 -25] or [-5 -35]
          corresponding to the RT20 and RT30 respectively.
      'correction' : {0.0025} | scalar
          Specifies the correction parameter C (in seconds) given above
          for DRR and CTE calculations. Values of up to 10 ms have been
          suggested in the literature.

  Octave-band filters are calculated according to ANSI S1.1-1986 and IEC
  standards. Note that the OCTDSGN function recommends centre frequencies
  fc in the range fs/200 < fc < fs/5.

  The author would like to thank Feifei Xiong for his input on the
  correction parameter.

  References

  [1] Zahorik, P., 2002: 'Direct-to-reverberant energy ratio
      sensitivity', The Journal of the Acoustical Society of America,
      112, 2110-2117.

  See also AUDIOREAD, OCTDSGN.

Acknowledgements

Octave inspired this file.

Required Products Signal Processing Toolbox
MATLAB release MATLAB 8.1 (R2013a)
MATLAB Search Path
/
Other requirements This function requires the Octave toolbox available on the FX: http://www.mathworks.co.uk/matlabcentral/fileexchange/69-octave
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Comments and Ratings (3)
14 Nov 2014 Christopher Hummersone

Hi Clay. I need a bit more information in order to help. Firstly, did you download the Octave toolbox per the requirements above (and add the files to your MATLAB search path)?

Comment only
13 Nov 2014 Clay Pipkin

An error comes up:

Error in IR_stats (line 164)
[b(f,:),a(f,:)] = octdsgn(cfs(f),fs,N);

Any thoughts?

Comment only
27 Jul 2013 Jose Ercolino  
Updates
15 Jul 2013 1.1

Minor to tweak to handling out-of-range te values.

19 Jul 2013 1.2

Minor tweak to file and updated screenshot.

10 Dec 2013 1.3

Made a number of tweaks: added more comments, added EDT output, and made slight modification to RT calculation so that y range can be specified and is [0 -60] by default.

11 Dec 2013 1.4

Corrected t0 estimation and H1 line.

03 Sep 2014 1.5

Changed inputs to accept parameter/value pairs, including new 'correction' parameter. Changed default correction.

19 Jun 2015 1.5.1

Added error trap for dynamic range in IR.

19 Jun 2015 1.5.2

A number of improvements and clarifications to the help. Some minor refactoring to improve the clarity of code.

19 Jun 2015 1.5.2

Updated description.

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