diff aim-mat/tools/@frame/frequencysharpening.m @ 0:74dedb26614d

Initial checkin of AIM-MAT version 1.5 (6.4.2011).

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/aim-mat/tools/@frame/frequencysharpening.m	Fri May 20 12:32:31 2011 +0100
@@ -0,0 +1,125 @@
+% method of class @frame
+% 
+%   INPUT VALUES:
+%  
+%   RETURN VALUE:
+%
+% 
+% (c) 2003, University of Cambridge, Medical Research Council 
+% Stefan Bleeck ([e-mail])
+% http://www.mrc-cbu.cam.ac.uk/cnbh/aimmanual
+% $Date: 2003/01/17 16:57:46 $
+% $Revision: 1.3 $
+
+function ret=frequencysharpening(current_frame,options)
+% frequency sharpening does local lateral inhibition according to its
+% parameters
+
+
+if nargin < 2
+    options=[];
+end
+
+
+if isfield(options,'excitatory_area') % how many erbs the excitation lasts
+    excitatory_area=options.excitatory_area;
+else
+    excitatory_area=0.5;
+end
+
+if isfield(options,'grafix') % how many erbs the excitation lasts
+    grafix=options.grafix;
+else
+    grafix=0;
+end
+
+if isfield(options,'inhibitory_area') % how many erbs the inhibition lasts
+    inhibitory_area=options.inhibitory_area;
+else
+    inhibitory_area=1.5;
+end
+
+if isfield(options,'inhibitory_influence') % how strong the inhibition is
+    inhibitory_influence=options.inhibitory_influence;
+else
+    inhibitory_influence=0.2;
+end
+
+
+cfs=getcf(current_frame);
+EarQ = 9.26449;				%  Glasberg and Moore Parameters
+minBW = 24.7;
+order = 1;
+ERB = ((cfs/EarQ).^order + minBW^order).^(1/order);
+B=1.019*2*pi.*ERB;
+
+vals=getvalues(current_frame);
+nr_chan=size(vals,1);
+nr_dots=size(vals,2);
+new_vals=zeros(size(vals));
+
+% calculate the interchannel crossinfluence for each channel
+erb1=21.4*log10(4.73e-3*cfs(1)+1);  % from Glasberg,Moore 1990
+erb2=21.4*log10(4.73e-3*cfs(nr_chan)+1);
+nr_erbs=erb2-erb1;
+erb_density=nr_chan/nr_erbs;
+neighbourinfluence=zeros(nr_chan);
+if grafix
+    figure(2)
+    clf
+end
+for i=1:nr_chan  % through all channels: prepare working variable
+    count=1;
+    for j=i-nr_chan:i+nr_chan  % calculate the influence of all channels
+        if j>0 & j< nr_chan 
+            dist=abs(i-j);  % we are symmetric
+            disterbs=dist/erb_density;  % so many erbs between the channel and me
+            
+            % the function(disterbs) to describe the influence of
+            % neighbouring channels:
+            %             final=1/disterbs;
+            
+            % Mexican hat function:
+            %             p=disterbs*disterbs/(threshold_decay_halflife*threshold_decay_halflife);
+            % version with power
+            %             final=(2-p)*exp(-0.5*p);
+            % version with difference from gaussians:
+            p1=disterbs*disterbs/(excitatory_area*excitatory_area);
+            p2=disterbs*disterbs/(inhibitory_area*inhibitory_area);
+            final=exp(-p1)-inhibitory_influence*exp(-p2);
+            
+            neighbourinfluence(i,count)=final;
+            count=count+1;
+        end
+    end
+    % normalize it
+    %     scale=1/sum(neighbourinfluence(i,:));
+    %     neighbourinfluence(i,:)=neighbourinfluence(i,:)*scale;
+    if grafix
+        figure(2)
+        plot(neighbourinfluence(i,:)); hold on
+        if i==30
+            plot(neighbourinfluence(i,:),'.-r','linewidth',3); hold on
+        end
+    end
+end
+
+for i=1:nr_dots % through the time
+    for j=1:nr_chan  % through all channels: prepare working variable
+        new_vals(:,i)=new_vals(:,i)+vals(:,i).*neighbourinfluence(:,j);
+    end
+end
+
+s=getfrequencysum(current_frame);
+current_frame=setvalues(current_frame,new_vals);
+
+ret=current_frame;
+
+if grafix
+    figure(3) ;clf;
+    s2=getfrequencysum(current_frame);
+    plot(s); hold on
+    ax=axis;
+    plot(s2,'.-r');
+    axis([0 58 0 40000]);
+end