Speech recognition for a newbie

Started by ngolehung84 July 17, 2009
Hi all,

I'm very new with both DSP and Speech recognition. So could you please
let me know:

+ What type of filters used to remove noise since my input is taken in a
noisy environment.
+ Some documents that discuss the frequency range of human voice?
+ Other types of filters?
+ Algorithms/techniques/models used to retrieve and match

These are all I think I need to work with speech recognition. If I miss
anything, please let me know.

I really appreciate if you guys can give me a hand to start studying
this field.

Thanks in advance,
Hey man!

To answer a few of your queries:
1) Noise Cancellation is a very hot research field and there are numerous methods to do so. I will suggest a few noise cancellation methods in the ascending order of difficulty - spectral subtraction (multiband inclusive), frequency scaling methods, kalman filtering, global soft decision method, signal subspace methods and auditory scene analysis / blind source separation. For just a start you would want to work on spectral subtraction.

Multiband spectral subtraction for speech enhancement [Sunil Devdas Kamant, MS Thesis]

speech enhancement for personal communications using an adaptive gain equalizer. Neils Westerlund, Mattias Dahl and Ingvar Claesson
2) Regarding the frequency range of human utterance, take it from me that it wont exceed 4kHz, so 8kHz sampling is just fine.
3) Other types of filters for noise cancellation: well, wavelets. but most filterbanks are used to split the signal into sub-bands.
4) Pattern Matching: just go through the chapter on HMMs from rabiner, or the famous tutorial for that matter... You just need to know how to fit a cluster of points in space into gaussians. That should give you a good start for speech recognition.