function overall = global_threshold(ATH, tone_power, noise_power, b)
% global_masking_threshold = global_threshold(absolute_threshold_of_hearing,
%                                             tone_power_spectral_density,
%                                             noise_power_spectral_density,
%                                             bark_spectrum)
%
% global_threshold takes the absolute threshold of hearing as well as the
% spectral densities of noise and tones to determine the overall global
% masking threshold.  This method assumes that the effects of masking
% are additive, so the masks of all maskers and the absolute threshold
% are added together.

% begin with zeros
temp1=zeros(1,length(tone_power));
%figure;
%hold on;
%plot(b(find(tone_power)), tone_power(find(tone_power)), 'rx');

% go through tone list
for k=find(tone_power),
   % determine the masking threshold around the tone
   [thres, start]=mask_threshold(1,k,tone_power(k),b);
   %plot(b(start:start+length(thres)-1), thres);
   % add the power of the threshold to temp in the proper frequency range
   temp1(start:start+length(thres)-1)=temp1(start:start+length(thres)-1)+dbinv(thres);
end
%plot(b,10*log10(temp1), 'c');
%xlabel('Frequency (Bark)');
%ylabel('Power (dB)');
%title('Tones and Related Thresholds');

temp2=zeros(1,length(noise_power));
%figure;
%hold on;
%plot(b(find(noise_power)), noise_power(find(noise_power)), 'ro');

% go through noise list
for k=find(noise_power)
   % determine the masking threshold around the noise masker
   [thres, start]=mask_threshold(0,k,noise_power(k),b);
   %plot(b(start:start+length(thres)-1), thres);
   % add the power of the threshold to temp in the proper frequency range
   temp2(start:start+length(thres)-1)=temp2(start:start+length(thres)-1)+dbinv(thres);
end
%plot(b,10*log10(temp2), 'c');
%xlabel('Frequency (Bark)');
%ylabel('Power (dB)');
%title('Noise and Related Thresholds');

temp=temp1+temp2;
% finally, add the power of the absolute hearing threshold to the list
for k=1:length(ATH),
   temp(k)=temp(k)+dbinv(ATH(k));
end

% all effects have been added, so now change to dB, the way everything else has been.
overall=10*log10(temp);