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SOFiA Impulse Response Reconstruction
This function recombines impulse responses or time domain signals for multiple channels from frequency domain data delivered by P/D/C or I/T/C. The internal IFFT blocklength is determined by the Y data itself: Y should have a size of [NumberOfChannels x ((2^n)/2)+1] with n={1, 2 ,3 , ...} (which is the case when using the SOFiA readVSAdata() or mergeArrayData() functions for data import) and the function returns [NumberOfChannels x resampleFactor*2^n samples. The impulse responses are windowed with a HANN window. The argument win can take values from 0-1. Where 0 means that no window is applied and 1 will apply a window to the full IR. At a value of 0.5 the first half of the impulse responses keeps unchanged and the last half is multiplied with a HANN type window. The size of the window is fitted automatically. As default choice win is set to 1/8 which should deliver good results in most of the cases. The impulse responses can be resampled to the original sampling rate before being downsampled in readVSAdata() or mergeArrayData(). Set resampleFactor = downSample to get back to the original sample rate of the measurement source material. (WARNING: Matlab Signal Processing Toolbox required for windowing and resampling)
To save processing power and calculation time the SOFiA chain works on the half-sided FFT spectrum only (NFFT/2+1). Therefore F/D/T produces half-sided spectrum output signals (fftData). The `makeIR()` function automatically reconstructs the double-sided spectrum to compute the impulse responses.
ARGUMENTS
Input
| Name |
Type |
Purpose |
Default |
| Y |
int |
Frequency domain data from P/D/C or
I/T/C |
- |
| win |
float |
Window IR tail [0-1] with a HANN window |
1/8 |
| resampleFactor |
float mtx |
Resampling factor |
1 |
Output
| Name |
Type |
Purpose |
| impulseResponses |
float mtx |
Impulse Responses
Rows: IR-Data
Cols: Channels |
FILE(S):
| File |
Type |
OS/Matlab |
| sofia_makeIR.m |
Help header, Function |
All OS |
HEADER
/*
impulseResponses = sofia_makeIR( Y, [win], [resampleFactor])
------------------------------------------------------------------------------------
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impulseResponses |
Reconstructed impulse response
Columns: Index / Channel: IR1, IR2, ..., IRn
Rows: Impulse responses (time domain)
|
------------------------------------------------------------------------------------ |
Y |
Frequency domain FFT data for multiple channels
Columns: Index / Channel
Rows: FFT data (frequency domain) |
[win] |
Window IR tail [0...1] with a HANN window
0 off
0-1 window coverage (a full, 0 off)
[default 1/8: 1/8 of the IR length is windowed]
! Signal Processing Toolbox required |
[resampleFactor] |
Optional resampling: Resampling factor
e.g. FS_target/FS_source
Resampling is done using MATLAB RESAMPLE
(See MATLAB documentation for more details)
! Signal Processing Toolbox required |
This function recombines impulse responses for multiple channels from
frequency domain data. It is made to work with half-sided spectrum FFT
data. The impulse responses can be windowed. The IFFT blocklength is
determined by the Y data itself:
Y should have a size [NumberOfChannels x ((2^n)/2)+1 with n=[1, 2, 3, ...]
and the funtion returns [NumberOfChannels x resampleFactor*2^n] samples.
Dependencies: MATLAB Processing Toolbox required for windowing and resampling |
*/ |
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