Thanks for your advice, junior. I am not retired but just happen to be interested in Machine Learning methods and this problem seems to be difficult enough since only few people have created anything that would even closely perform at skilled human operator level. I did investigate some speech recognition algorithms such as HMM and SOM. I have spent also some time collecting data and training software to recognize real world noisy and messy signals. In fact the current shipping version of FLDIGI package has one of these algorithms (SOM) built in.
I don't have a PhD in related field but I have studied signal processing and even wrote some software for MRI image reconstruction and processing earlier in my career. The papers I have read on speech recognition over the last 20 years have certainly improved the state of the art but the methods are more incremental improvements than some ground breaking new discoveries.
BTW - How is that Siri working for you in a noisy car with windows open at highway speed? Humans can still understand each others in this kind of conditions.