clear all
for h=1:20
fname=sprintf('D:\\study\\音頻采樣\\noise22050hz\\%d.wav',h);
x=wavread(fname);
x=x(:,1);
[c,l]=wavedec(x,3,'db4');
ca=appcoef(c,l,'db4',3);%近似系數(shù)
x=ca;
enframex=enframe(x,128,64);%對(duì)信號(hào)x分幀處理，每幀有128個(gè)采樣點(diǎn)，相鄰幀之間有50%的疊加率
[row,col]=size(enframex);%返回行，列，每一行代表一幀，每一列表示1到128個(gè)采樣點(diǎn)
framelen=col;
frameinc=64;  
hang=row;%計(jì)算出分幀后語音矩陣的行數(shù)
temp1=enframe(x,framelen,frameinc);%將分幀后的數(shù)據(jù)存入temp1數(shù)組矩陣
for i=1:hang;
 j=1:frameinc;
    z(i)=max(temp1(i,j));%求第i幀前frameinc個(gè)元素最大值并存入z(i)數(shù)組中
end
for i=1:hang;
 j=framelen-frameinc:framelen;
    a(i)=max(temp1(i,j));
end
i=1:hang;
c(i)=min(z(i),a(i))*0.68;%計(jì)算每幀的門限值
for i=1:hang;
 for j=1:framelen;
    if temp1(i,j)>c(i)
        y(i,j)=temp1(i,j)-c(i);
    else if abs(temp1(i,j))<=c(i)
            y(i,j)=0;
        else if temp1(i,j)<c(i)*(-1)
                y(i,j)=temp1(i,j)+c(i);
            end 
        end
    end
 end
end
for i=1:hang;
if (j>=0)&(j<=20)
    y(i,j)=0;
end
end   %將0到20點(diǎn)置零
for i=1:hang;
   for j=framelen:450;
       y(i,j)=0;  %將framelen點(diǎn)到450點(diǎn)的值置零
       
   end
end
    
for i=1:hang;
   for j=1:framelen;
    if y(i,j)>0
        y1(i,j)=1;
    else if y(i,j)==0;
            y1(i,j)=0;
        else if y(i,j)<0
                y1(i,j)=-1;
            end
        end
    end
end
end
for i=1:hang;
if (j>=0)&(j<=20)
    y1(i,j)=0;
end
end   %將0到20點(diǎn)置零
for i=1:hang;
   for j=framelen:450;
       y1(i,j)=0;  %將framelen點(diǎn)到450點(diǎn)的值置零
   end
end
       
       
for i=1:hang;
    for k=1:128;
    n=21:framelen;
    R(i,k)=sum(y(i,n).*y1(i,n+k));
end
end
%計(jì)算每一幀y與y1的互相關(guān)值
for i=1:hang;
    k=20:128;
Rmax(i)=max(R(i,k));%計(jì)算每幀的Rmax值
end
for i=1:hang;
    k=20:128;
    [r,kmax(i)]=max(R(i,k));%找出每幀Rmax對(duì)應(yīng)的k值kmax
end
  
for i=1:hang;
    if Rmax(i)<0.25*R(i,1)
        P(i)=0;
    else P(i)=kmax(i);
    end
end

noise(h)=0;
for i=1:hang-1;
    if P(i)==P(i+1)
       noise(h)=noise(h)+1;
    end
end
noisebi(h,1)=noise(h)/hang;
end
noisebi