How to make speech content conversion by a word replacement?

I am working on a project to record an audio file(a sentence with 10-15 words) and sound it. Then I needed to write a code to seperate the words and save them as individual .wav files.

[speech,fs]=audioread('tenwords.wav'); 
sp=100;  
threshold=1;
k_s=0;
window= sp*fs/1000; 
speech2 = speech(1:(length(speech)-mod(length(speech), window)),1); 
samples = reshape(speech2,window,length(speech2)/window); 
energies = sqrt(sum(samples.*samples))'; 
vuv = energies > threshold; 
z=length(energies);
a=1;
t=1;
j;
for j=1:z
    if((vuv(j)==1) && (vuv(j+1)==0))
        k_s=k_s+1;
    end
end
bas=zeros(1,k_s);
for i=1:k_s 
    for k=a:z
        if((vuv(k)==0) && (vuv(k+1)==1)); break;
        end
    end
    a=k+1;
    bas(i)=k*4800;
end
son=zeros(1,k_s);
for e=1:k_s
    for r=t:z
        if((vuv(r)==1) && (vuv(r+1)==0)); break;
        end
    end
    t=r+1;
    son(e)=r*4800;
end
for x=1:k_s
    kelime=bas(x):son(x);
    filename = ['C:\Users\hp\Desktop\Words\d' ,x+48, '.wav'];
    audiowrite(filename, speech(kelime),fs);
end

But when I try to listen the output audio files, there is 10 .wav files, it is ok, but their speech content(the word that they stored) is not understandable. I don't have any idea what is the problem in my project. Can anyone help me to fix this?

(I also need to create random sentences with that 10 words as a next step.)