Sphinx4 is a Java speech recognition library that uses the Java Speech API engine. It requires four attributes to be set for recognition: an acoustic model, dictionary, grammar or language model, and audio source. The acoustic model represents sound patterns, the language model is a word probability distribution, and grammars precisely define possible inputs. Important Sphinx4 packages provide frontend utilities, recognition classes, result representations, and property management.

2. Sphinx4 is a pure Java speech recognition library.
Sphinx4 is a set of classes which use Java Speech
API(JSAPI) as speech recognition engine
Four attributes to be set up for a speech recognition
job:
i. Acoustic model
ii. Dictionary
iii. Grammar/Language model
iv. Source of speech
First three attributes are setup using Configuration
object which is passed then to a recognizer

3. Acoustic model is used to represent relationship
between an audio signal and phonetic units in the
language.
A statistical language model is a probability
distribution over sequences of words.
Grammars allow to specify possible inputs very
precisely.
Grammars could be created with JSGF format
and usually have extension like .gram or .jsgf.

4. Important Sphinx packages used in a program:
edu.cmu.sphinx.frontend.util-Provides classes
that are generally useful to the various frontend
classes.
edu.cmu.sphinx.recognizer-Provides a set of
high level classes and interfaces that are used to
perform speech recognition with the Sphinx-4 speech
recognition system.
edu.cmu.sphinx.result-Provides a set of
classes that represent the result of a recognition.
edu.cmu.sphinx.util.props-Provides a
mechanism for managing persistent configuration
data.

5. Architecture of Sphinx4