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Step 7 - Fixing the Silence Models


In the last step you created HMM models that did not include an "sp" (short pause) silence model - which refers to the types of short pauses that occur between words in normal speech.  However, you did create a "sil" silence model - sil silence models are typically of longer duration, and refer to the pauses occur at the end of a sentence.   

The HTK book says that the sp model needs to have its "emitting state tied to the centre state of the silence model".  What this means is that you need to create a new sp model in your hmmdefs, that it will use the centre state of sil, and then they both need to be 'tied' together (for a bit of background on HMMs and states).

This can be done by copying the centre state from the sil model in your hmmdefs file and adding it to the sp model, and then running a special tool called HHED to 'tie' the sp model to the sil model so that they share the same centre state.  The HTK book provides some background on what this means, but you need an understanding of the basics of Hidden Markov Modelling before tackling the HTK Book explanations (the University of Leeds HMM tutorial provides a very good tutorial on Hidden Markov Modelling).

Note: you do not need to understand HMMs to complete this tutorial.


First copy the contents of the hmm3 folder to hmm4.  Then using an editor, create new "sp" model in hmm4/hmmdefs as follows:

  • copy and paste the “sil” model and rename the new one “sp”(don't delete your old "sil" model, you will need it - just make a copy of it)
  • remove state 2 and 4 from new “sp” model (i.e. keep 'centre state' of old “sil” model in new “sp” model)
  • change <NUMSTATES> to 3
  • change <STATE> to 2
  • change <TRANSP> to 3
  • change matrix in <TRANSP> to 3 by 3 array
  • change numbers in matrix as follows:
 0.0 1.0 0.0
 0.0 0.9 0.1
 0.0 0.0 0.0

Your sp model should look something like this:

~h "sp"
<MEAN> 25
 -7.118713e+00 -3.081000e-01 -1.749457e+00 -1.031217e+00 -1.165559e+00 3.531405e+00 3.928634e+00 1.414117e+00 4.853880e+00 3.436303e+00 8.821907e-01 3.578307e+00 -7.581001e-02 -5.415154e-02 2.016401e-01 -8.739231e-02 4.121462e-02 8.872373e-02 -7.476506e-02 9.644009e-03 1.259353e-01 -1.379244e-01 -3.326035e-02 1.257626e-01 1.159135e-01
 8.348813e+00 8.595272e+00 1.137517e+01 1.209942e+01 8.636264e+00 1.499810e+01 9.930653e+00 1.164548e+01 1.039156e+01 8.853771e+00 8.320317e+00 9.811087e+00 9.367380e-01 7.999393e-01 1.583295e+00 9.593871e-01 7.300864e-01 1.651675e+00 1.296489e+00 9.965155e-01 1.218978e+00 1.052432e+00 9.433080e-01 1.521487e+00 5.511271e-01
<GCONST> 7.427084e+01
 0.0 1.0 0.0
 0.0 0.9 0.1
 0.0 0.0 0.0

Your files should look like this:

Next, run the HMM editor called HHEd to "tie" the sp state to the sil centre state - tying means that one or more HMMs share the same set of parameters.  To do this you need to create the following HHEd command script, called sil.hed, in your voxforge/tutorial folder:

AT 2 4 0.2 {sil.transP}
AT 4 2 0.2 {sil.transP}
AT 1 3 0.3 {sp.transP}
TI silst {sil.state[3],sp.state[2]}

The last line is the "tie" command.  Next run HHEd as follows, but using the monophones1 file which contains the sp model:

HHEd -A -D -T 1 -H hmm4/macros -H hmm4/hmmdefs -M hmm5 sil.hed monophones1

The files created by this command are:

Next run HERest 2 more times, this time using the monophones1 file: 

HERest -A -D -T 1 -C config  -I phones1.mlf -t 250.0 150.0 3000.0 -S train.scp -H hmm5/macros -H  hmm5/hmmdefs -M hmm6 monophones1

The files created by this command are:


HERest -A -D -T 1 -C config  -I phones1.mlf -t 250.0 150.0 3000.0 -S train.scp -H hmm6/macros -H hmm6/hmmdefs -M hmm7 monophones1

The files created by this command are:



By Lefteris - 5/14/2015 Hi. I have been trying to create a model for single digit detection, but I kept it at word-level (no phones). What I wanted to do was incorporate the silence model.

By iamashutoshks - 4/8/2015 - 1 Replies How are we suppose to get the 3x3 matrix for "sp" model.Should we copy the values given in the tutorial or is there any other way of computing it? Please help.

By Olumide - 1/23/2013 - 1 Replies I'm get the following error when trying to create hmm6. Which file do I have to fix?

By Nitish - 6/28/2012 My label files don't have a 'sp' phoneme. So should I still need to creat a 'sp' phoneme and use HHed to tie it together with 'sil'?

By fkrafi - 5/6/2012 - 1 Replies Can anyone help me?????

By khanh - 5/31/2011 - 1 Replies I wonder why TRANSP matrix is

By mawahib - 4/16/2011 - 1 Replies HHEd -A -D -T 1 -H hmm4/macros -H hmm4/hmmdefs -M hmm5 sil.hed monophones1

By mawahib - 4/15/2011 - 8 Replies Summarized post:

By mawahib - 4/11/2011 - 2 Replies

By mawahib - 4/11/2011 - 1 Replies I will use 6 states, how I will choose the state in the middle of the model?

By Alexandra - 1/27/2011 - 3 Replies Hello,

By Visitor - 3/15/2010 - 3 Replies can anyone solve my problem at step 7????

By Tom - 3/12/2010 - 1 Replies Do any one know what is the reason for HERest not permitting successive Tee models ? Any pratical or conceptual reason behind that?

By puphe_88 - 1/1/2010 - 1 Replies what the contains file of phones1.mlf when compile hmm6 , hmm7 ??

By abinew A - 11/22/2009 - 1 Replies administrator@home-1c4b4e8ca9 /home/voxforge/manual i face a problem when executing the following command so as to create hmm6/hmmdefs and hmm6/hmmdefs:

By joshuajnoble - 6/6/2009 - 4 Replies I get the following error when I run the HERest command:

By zvaracik - 5/20/2009 - 1 Replies I try this manual for create grammar recognition engine. But tutorial in this page I found a mistake.

By kmaclean - 3/15/2009 - 3 Replies from this post by kalmanbucy:

By MrNice - 3/9/2009 - 7 Replies Hi,

By Manuel - 9/6/2007 - 3 Replies When I execute: HERest -A -D -T 1 -C config -I phones1.mlf -t 250.0 150.0 3000.0 -S train.scp -H hmm5/macros -H hmm5/hmmdefs -M hmm6 monophones1 It give me this error ERROR [+7332] CreateInsts: Cannot have successive Tee models FATAL ERROR - Terminating program HERest I check all the previous file in hmm5, and they are like the example of the tutorial. Someone can help me? Tks