<p>It works only for gaussian noise, but with almost every level of noise.
It could be used to remove some other kind of noises, but that's not guaranteed. 
However if you look at Matlab documentation it says that uses a pre-trained model called "DnCNN". 
So i think that could be useful to see the relative paper: 
<a href="https://arxiv.org/abs/1608.03981" rel="nofollow noreferrer">link to paper</a></p>
Is 'denoisingNetwork' in 'denoiseImage' specific to one noise?
<p>What kind of noise removal training does the function 'denoisingNetwork' do, which is used as a part of 'denoiseImage'? Is it specific to some kind of noise and noise level or just a generalized network that gives an average output image?</p>