Added RMS levels of DUT and REF signals at soundcard input.

mataa_tools/mataa_guess_IR_start.m

@@ -20,7 +20,7 @@
 % EXAMPLE:
 % > [h,t] = mataa_IR_demo; % load demo data of an loudspeaker impulse response.
 % > mataa_plot_IR(h,t); % plot the fake signal
-% > [t_start,t_rise] = mataa_guess_IR_start(h,t,200)
+% > [t_start,t_rise] = mataa_guess_IR_start(h,t,20)
 %
 % This gives t_start = 0.288 ms and t_rise = 0.0694 ms. In this example might therefore safely discard all data with t < t_start. In real-world use (with noise and Murphy's law against us), however, it might be worthwile to add some safety margin, e.g. using t_rise: discard all data with t < t_start - t_rise.
 % 
@@ -62,8 +62,8 @@
 
 if ~isempty (fc) % apply high-pass filter to remove low-frequency noise
 	fn = fs/2; % Nyquist frequency	
-	[b,a]=butter (4,fc/fn,'high'); % 4th order high-pass Butterworth filter
-	h = filter(b,a,h);	
+	[b,a] = butter (4,fc/fn,'high'); % 4th order high-pass Butterworth filter
+	h = filter(b,a,h);
 end
 
 badShape = 'mataa_guess_IR_start: the signal does not look like a well-shaped impulse response.';

mataa_tools/mataa_measure_HD.m

@@ -1,6 +1,6 @@
-function [THD,kn,f1] = mataa_measure_HD (f1,T,fs,N);
+function [THD,kn,l0DUT,l0REF] = mataa_measure_HD (f1,T,fs,N);
 
-% function [THD,kn] = mataa_measure_HD (f1,T,fs,N);
+% function [THD,kn,l0DUT,l0REF] = mataa_measure_HD (f1,T,fs,N);
 %
 % DESCRIPTION:
 % This function measures harmonic distortion using a sine wave with a given frequency.
@@ -15,6 +15,7 @@
 % THD = total harmonic distortion, see below.
 % kn: harmonic distortion spectrum, in voltage units (not power). kn is a vector containing the harmonic components (k1, k2, k3, ... kN), where k1 corresponds to f1. The spectrum is normalised such that k1 is equal to one.
 % f1: true value of f1 used for analyses (value may be adjusted slightly to fit in the resolution of the fourier spectrum).
+% l0DUT, l0REF: RMS level of the DUT and REF signals at the soundcard input (useful for repeated tests at different levels)
 %
 % NOTE 1: THD is computed WITHOUT the noise in the spectrum ranges between the harmoics.
 %
@@ -74,7 +75,7 @@
 
 %x = [ z ; x ; z ];
 
-[out,in] = mataa_measure_signal_response(x,fs,0.1);
+[out,in] = mataa_measure_signal_response(x,fs);
 
 yDUT=out(:,mataa_settings('channel_DUT'));
 yREF=out(:,mataa_settings('channel_REF'));
@@ -95,6 +96,10 @@
 yDUT = yDUT.*w;
 yREF = yREF.*w;
 
+% pre-normalize signals by their RMS value
+l0DUT = sqrt (sum(yDUT.^2)) / length (yDUT); yDUT = yDUT / l0DUT;
+l0REF = sqrt (sum(yREF.^2)) / length (yREF); yREF = yREF / l0REF;
+
 % calculate signal spectra (voltages!)
 [YDUT,f] = mataa_realFT(yDUT,t);
 [YREF,f] = mataa_realFT(yREF,t);
@@ -120,7 +125,7 @@
 
 i = find(kn < 0);
 if any(i)
-    warning('mataa_measure_HD: some signal harmonics are negative. Is the REF signal clipped or otherwise corrupted?');
+    warning('mataa_measure_HD: some signal harmonics are negative. Is the REF signal clipped or otherwise corrupted? Too much noise?');
 end
 
 THD = sqrt( sum( kn(2:end).^2 ) ) / kn(1);