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%% Measuring a transfer function with the ITA Toolbox
%
% In this tutorial you will learn how to measure a transfer function 
% with the ITA Toolbox. The tutorial builds on the 'ita_tutorial_record'
% tutorial and will only explicitly explain new settings.
%
% <ITA-Toolbox>
% This file is part of the ITA-Toolbox. Some rights reserved.
% You can find the license for this m-file in the license.txt file in
% the ITA-Toolbox folder.
% </ITA-Toolbox>
%
% For feedback or questions, please contact the ITA Toolbox developers:
% toolbox-dev@akustik.rwth-aachen.de
%
% JCK 2017

%% Set Hardware
% Set your recording hardware in 'IO Settings'-tab ('recording' and
% 'playback device'). For a calibrated measurement it is also
% recommended to check 'Measurement Chain' on the % same 'IO Settings'
% tab.
ita_preferences;
ccx;

%% Measurement Setup
% Create an instance of  the transfer function measurement class.
MS = itaMSTF;
% Specify an excitation signal. Possible choices are:
% 'exp' : exponential sweep
% 'lin' : linear sweep
% 'noise': white noise
% itaAudio() : any itaAudio variable can be saved here
MS.type = 'exp';
% The output measurement chain consists of 3 elements (D/A converter, 
% amp and actuator for the output). If your measurement involves 
% calibrating a loudspeaker you should be an expert user, since this is
% not a trivial question. As a beginner you can leave your output
% measurement chain uncalibrated.
MS.inputChannels = 1; % for multiple channels (e.g. 1, 2 & 3): [1 2 3] 
MS.outputChannels = 1; % for multiple channels (e.g. 1, 2 & 3): [1 2 3] 
MS.fftDegree = 19;
MS.samplingRate = 44100;
% Since our system will usually have a response decay time (in room
% acoustics: reverberation time), we need to make sure the last bit of
% measurable energy can arrive at our input. Therefor we define a 
% waiting time at the end of the measurement during which the system 
% will record that last bit. This value should at least be equal to the
% decay time for the last sent out part of the signal (e.g. the 
% reverberation time for the highest frequency of the excitation sweep).
MS.stopMargin = 0.3;
% We need to specify the output volume of our system. This can either be
% done by adjusting the output settings of your amp (by turing a knob,
% flipping a switch, etc.) or by digitally manipulating the amplitude of
% the excitation signal. The unit of the specified value is dBFS (dB 
% Full Scale), the dB distance to the maximum digital signal amplitude 
%of the measurement system.
MS.outputamplification = -30;
% Have a look.
MS

%% Calibration
% The calibration process basically stays the same, just with more
% possible elements to calibrate. The input is calibrated first. The 
% electrical parts of the output chain (D/A and amp) need to be rewired 
% to the input for calibration. make sure to select the right input
% element in the output calibration GUI (e.g. preamp). At the same time
% the calibration process measures the delay caused by the D/A and A/D% 
% processes and stores it in numbers of latency samples.
MS.calibrate;
% Have a look
MS.latencysamples


%% Measurement
% After the execution of the measurement the raw recording will be 
% deconvoluted using the excitation signal. The result is an impulse
% response (time domain) or transfer function (frequency domain).
result = MS.run;

% Have a look at the result in the time domain (.plot_time or pt)
result.pt
result.ptd
result.pf