From 0d4e517b0dfa041fcb09444cbc221c634f0a3922 Mon Sep 17 00:00:00 2001 From: Markus Mueller-Trapet Date: Wed, 29 Nov 2017 16:04:33 -0500 Subject: [PATCH] add static pressure as input option --- kernel/DSP/ita_sound_power.m | 22 ++++++++++------------ 1 file changed, 10 insertions(+), 12 deletions(-) diff --git a/kernel/DSP/ita_sound_power.m b/kernel/DSP/ita_sound_power.m index 3c3a33e..7598df6 100644 --- a/kernel/DSP/ita_sound_power.m +++ b/kernel/DSP/ita_sound_power.m @@ -14,6 +14,7 @@ function varargout = ita_sound_power(varargin) % chamber % 'T' (20) : Temperature in deg Celsius % 'RH' (0.5) : Relative Humidity +% 'p_s' (101325) : Static pressure in Pa % % Example: % audioObjOut = ita_sound_power(audioObjIn) @@ -31,17 +32,19 @@ function varargout = ita_sound_power(varargin) % Author: Christian Haar -- Email: christian.haar@akustik.rwth-aachen.de % Created: 24-Jun-2010 +% Re-write to conform with ISO 3741: Markus Mueller-Trapet -- Email: markus.mueller-trapet@nrc.ca +% Modified: 28-Nov-2017 %% Initialization and Input Parsing -sArgs = struct('pos1_spl', 'itaSuper', 'pos2_T_empty', 'itaSuper', 'room_volume', 124,'room_surface',181,'T',20,'RH',0.5, 'freqRange', ita_preferences('freqRange'), 'bandsPerOctave', ita_preferences('bandsPerOctave') ); +sArgs = struct('pos1_spl', 'itaSuper', 'pos2_T_empty', 'itaSuper', 'room_volume', 124,'room_surface',181,'T',20,'RH',0.5,'p_s',101325, 'freqRange', ita_preferences('freqRange'), 'bandsPerOctave', ita_preferences('bandsPerOctave') ); [spl,T_empty,sArgs] = ita_parse_arguments(sArgs,varargin); % acoustic constants c = 20.05*sqrt(273 + sArgs.T); +Z_0 = itaValue(400,'kg/(m^2*s)'); % this is the fixed value to get the reference for 1pW right % correction factors for the meteorological conditions (not in dB!) -% (assumes static pressure is the reference value) -C1 = sqrt((273.15 + sArgs.T)/314); -C2 = sqrt((273.15 + sArgs.T)/296).^3; +C1 = 101325./double(sArgs.p_s).*sqrt((273.15 + sArgs.T)/314); +C2 = 101325./double(sArgs.p_s).*sqrt((273.15 + sArgs.T)/296).^3; %% calculate sound pressure level data % first third-octaves then average @@ -53,14 +56,9 @@ spl_m = itaResult(spl_m,T_empty.freqVector); A = 55.26*itaValue(double(sArgs.room_volume)/c,'s*m^2')/T_empty; %% calculate sound power (Eq 20 in ISO 3741) -sound_power = spl_m^2 * A * 10^(-6/10) * C1 * C2; -% exponent and frequency-dependent part -sound_power.freq = sound_power.freq.*exp(A.freq./double(sArgs.room_surface)).*(1 + double(sArgs.room_surface)*c./(8*double(sArgs.room_volume).*sound_power.freqVector)); -% getting the reference values right -sound_power = sound_power*itaValue(1e-12,'W')/itaValue(20e-6,'Pa')^2/itaValue(1,'m^2'); - -% or the straight-forward way: -% sound_power = spl_m^2 * A/(2*itaValue(c,'m/s')*itaValue(1.2,'kg/m^3')); +sound_power = spl_m^2 * A /(4*Z_0); +% apply exponent and frequency-dependent corrections +sound_power.freq = C1.*C2.*sound_power.freq.*exp(A.freq./double(sArgs.room_surface)).*(1 + double(sArgs.room_surface)*c./(8*double(sArgs.room_volume).*sound_power.freqVector)); %% Add history line sound_power = ita_metainfo_add_historyline(sound_power,mfilename,varargin); -- GitLab