Hi Hema, the general way feature extraction works for signals is that a set of features is extracted for every buffer of samples. The longer the file, the higher the number of buffers fitting across its whole length. This is why you are seeing a variable number of feature row for each audio file - because each audio file has different number of audio samples.
audioFeatureExtractor by default uses hamming windows of 1024 samples (around 23ms at 44.1kHz), overlapping by 512 samples. You can get it to use whatever window length, though usually the length is set based on the type of signal and which type of signal characteristic you think will be most discriminative for your problem.
If you are really looking for only a single row a features per file, then you may want to apply some kind of averaging netric (e.g. mean, median, ...) across the rows of the feat array. In the code above that would happen after the use of isVoicedSpeech, if relevant. For example:
% [...]
feat(~voicedSpeech,:) = [];
feat = median(feat,1);
label = adsInfo.Label; % (no more need to size-extend file label)
% [...]
I hope this helps.
