Earlier quoted context omitted.
There is a second paper where they specifically point out the differences between their approach and previous approaches using neural networks and it isn't only the number of layers that has changed but also the internal architecture of the network, the "responsibilities" of the layers, so again, it isn't just a traditionally trained MLP with a lot of layers: http://research.microsoft.com/pubs/157341/FeatureEngineeri…
I read it in diagonal but the paper seems to use the same DNN architecture as before. They seem to tweak the pretraining with layer-wise back-propagation (instead of full MLP-as-DBN pre-training). This does not imply anything new with respect to what I commented and the cited paper. The only reference to differences I found is about differences between a DNN and a MaxEnt models, which is again not an argument for dif…
http://en.wikipedia.org/wiki/Autoencoder
I am not very familiar with speech recognition, but I think what they talk about here:
Instead of factorizing the networks, e.g., into a monophone and a context-dependent part [5], or decomposing them hierarchically [6], CD-DNN-HMMs directly model tied context-dependent states (senones). This had long been considered ineffective, until [1] showed that it works and yields large error reductions for deep networks.
might be related to this fact. 20 years ago it wasn't known why would you pick a deep network instead of a shallow one, there was even this famous theorem of Kolmogorow that a lot of people in ML misunderstood, that a network with just one hidden layer can in theory learn any function with arbitrary precision.