how to downsample a audio having sampling rate 44100 Hz to 2000Hz in matlab? This is the program i used but it showing error. how to rectify it?

[x, fs1] = audioread('audio8.wav');
    ts1=1/fs1;
    N1=length(x);
    Tmax1=(N1-1)*ts1;
    t1=(0:ts1:Tmax1);
    figure;
  plot(t1,x),xlabel('Time'),title('Original audio');
   [y,fs2]=downsqample(x,20,441);
   ts2=1/fs2;
   N2=length(y);
   Tmax2=(N2-1)*ts2;
   t2=(0:ts2:Tmax2);
   figure;
   plot(t2,y),xlabel('Time'),title('downsampled audio');

[madhan ravi]

What’s the error message paste everything in red here

[SUCHITHRA K S]

Error using downsample Too many output arguments.

Error in project (line 8) [y,fs2]=downsample(x,20,441);

Answer 1

[madhan ravi]

Should be downsample but you wrote it as downsqample

[madhan ravi]

downsample only should have one output but you have two that’s causing the error

[SUCHITHRA K S]

i didnt get you. can you explain it

[madhan ravi]

[y,fs2]=downsample(x,20,441);

Should be

y=downsample(x,20,441);

[SUCHITHRA K S]

but i have to plot that downsampled audio then how i will plot if i remove fs2 ?

[SUCHITHRA K S]

now it showing a error like this

Error using updownsample>parseUpDnSample (line 55) Offset must be from 0 to N-1.

Error in updownsample (line 17) phase = parseUpDnSample(str,N,varargin{:});

Error in downsample (line 33) y = updownsample(x,N,'Down',varargin{:});

Error in project (line 8) y=downsample(x,20,441);

>>

[madhan ravi]

I don’t have any experience in audio sampling but what I am sure that downsample() should have only one output

[SUCHITHRA K S]

ok

[Walter Roberson]

For those inputs you probably want resample not downsample.

resample does permit two outputs but the second is not fs2. Your fs2 should be 20/441*fs1

[SUCHITHRA K S]

[x, fs1] = audioread('audio2.wav');
sound(x,fs1);
   ts1=1/fs1;
    N1=length(x);
    Tmax1=(N1-1)*ts1;
    t1=(0:ts1:Tmax1);
    figure;
  plot(t1,x),xlabel('Time'),title('Original audio');
  fs2 = (20/441)*fs1;
  y=downsample(x,20,441);
  sound(y,fs2);
   ts2=1/fs2;
   N2=length(y);
   Tmax2=(N2-1)*ts2;
   t2=(0:ts2:Tmax2);
   figure;
   plot(t2,y),xlabel('Time'),title('downsampled audio');

i tried the code but the error is like this,

Error using updownsample>parseUpDnSample (line 55)
Offset must be from 0 to N-1.

Error in updownsample (line 17)
phase = parseUpDnSample(str,N,varargin{:});

Error in downsample (line 33)
y = updownsample(x,N,'Down',varargin{:});

Error in project (line 10)
  y=downsample(x,20,441);

[Walter Roberson]

Read the documentation for downsample:

    downsample(X,N) downsamples input signal X by keeping every
    N-th sample starting with the first. If X is a matrix, the
    downsampling is done along the columns of X.

    downsample(X,N,PHASE) specifies an optional sample offset.
    PHASE must be an integer in the range [0, N-1].

I believe that what you want to do instead is to rate convert 44100 Hz to 22000 Hz, which is a ratio of 22 out of 441 . To do that you would use resample not downsample

[SUCHITHRA K S]

if true
  % code
end
[x, fs1] = audioread('audio2.wav');
%sound(x,fs1);
 ts1=1/fs1;
  N1=length(x);
  Tmax1=(N1-1)*ts1;
  t1=(0:ts1:Tmax1);
  figure;
plot(t1,x),xlabel('Time'),title('Original audio');
fs2 = (20/441)*fs1;
y=resample(x,2000,44100);
%sound(y,fs2);
 ts2=1/fs2;
 N2=length(y);
 Tmax2=(N2-1)*ts2;
 t2=(0:ts2:Tmax2);
 figure;
 plot(t2,y),xlabel('Time'),title('resampled audio');
 spectrogram(y, 256, [], 25, 2000, 'yaxis');

when i plot the spectrogram of the resampled signal it showing the error like this ">> resam Error using spectrogram>chkinput (line 252) X must be a vector (either row or column).

Error in spectrogram (line 166) chkinput(x);

Error in resam (line 18) spectrogram(y, 256, [], 25, 2000, 'yaxis');

>> " how to rectify it?

[Walter Roberson]

Your audio contains multiple channels, which is fine for resample(). However spectrogram can only process one channel.

[SUCHITHRA K S]

then what is the comment for plotting the spectrogram of resampled audio

[Walter Roberson]

nchan = size(y,2);
for chan = 1 : nchan
  subplot(1, nchan, chan)
  spectrogram(y(:,chan), 256, [], 25, 2000, 'yaxis');
  title( sprintf('spectrogram of channel #%d', chan) );
end

[SUCHITHRA K S]

ok thank you.

[madhan ravi]

Thank you sir Walter . @Suchithra you can appreciate the persons time by accepting the answer and also it indicates the question is solved

[atek]

Sir Walter indeed, as usual. @SUCHITHRA K S, I strongly 2nd @madhan ravi's comment