Tuesday, May 10, 2016

Phonetics: 2500 year old Sanskrit grammar in BNF form

In last post I talked about the Syntax parsing and special X-Bar theory that applies to the natural languages. In this post we'll start our exploration with 2500 years old grammar in Backus Naur Form and move to internal structure of words and syllables.


My mother tongue is Marathi Language which is a daughter language of Sanskrit  and preserves most of the grammatical features of Sanskrit including 8 cases, 3 genders. 50% of the vocabulary is directly from Sanskrit (tat-sama ) and another 25% can be derived by single sound shift (tat-bhava).

3 years of Painful High School Grammar

I took 3 years of Sanskrit in high school but all I remember is sheer pain learning its grammar.
  • Imagine all those latin conjugation and declination tables ? Well ! Sanskrit has 10 times more tables.
  • You think French liaison and ellisions are hard ? Sanskrit has most such rules for sound changes.
  • You think German has long words ? Yes, Sanskrit has that as well. Including famous splitting of prefix and the main verb.


Panini's Grammar

The most authoritative grammar of sanskrit is actually formulated using form similar to modern context free grammars.
  • Panini developed his Grammar around 500 BC
  • He used 14 classes of phonemes and taking that as lexical terminal symbols of his grammar described Sanskrit grammar as set of 3,959 rules to describe all grammatically correct ways to construct Sanskrit sentence.


The word factory 

Human - a talking animal 

Despite our differences all humans are born with an ability for the language most human languages have following properties
  • 30-60 sounds that are put together to make syllables.
  • The syllables are put together to make words
  • words form phrases
  • phrases form sentences 
  • sentences form discourse 

Structure of Words and Syllable




How human voice is produced.

Human speech articulation begins in the larynx. The vibrations created there are modified through out the vocal tract which ultimately comes out of the mouth as series of sounds which we understand as sequence of phonemes. Larynx is where the "voice" starts but that sound is progressively modified in the mouth by forming various shapes with our tongue and lips. I have modified the standard diagram to show the schematic of the vocal tract. The most important key concept is this: Our tongue is a very flexible muscle that can form various shapes and that profoundly affects the way we perceive the basic sound that begins at the larynx.  [Edited from original here : http://en.wikipedia.org/wiki/File:Illu01_head_neck.jpg.]
That brings us to the next concept. There are two types of sounds viz. vowels and consonants.
When the airflow from larynx is not obstructed we perceive that sound. Anyone how has dealt with waveform of human sound knows that most of the waveform is basically sound of vowels. However the most interesting sounds are generated when the airflow is blocked (or substantially modified) for the brief amount of time. This time frame is seriously tiny compared to rest of the vowel sound and we perceive it as consonant.
In terms of digital signal processing the waveform of the voice that starts in larynx is modified by the resonance of the vocal tract and therefore we apply the convolution of the simplified model on the right side.


Vowels take most of the time in speech signal. All consonants are meaningful only in the context of background of robust vowel signal.  The larynx is actively producing "voice" during the vowels.
The quality of vowel depends on  four attributes.
  1. Height of tongue position- In other words whether the gap between tongue and roof of mouth is closed or open. generally four positions are considered. Open, Open mid,Close mid and Close.
  2. Position of tongue - Front, central or back
  3. Roundness of lips - The roundness of lips add another effect.  They are generally rounded for back vowels.
  4. Nasalization ? are the vowels nasalized.
Below is the list of known vowels and their IPA symbols.

Edited from original here : http://en.wikipedia.org/wiki/File:IPA_chart_2005_png.svg

The best way to analyze vowels is to look at their frequency spectrogram and look at the peaks. The first three formant are specifically interesting. The roundness of lips changes the positions of formant.
Again there are further diphthongs and glides that are combination of  two vowels.


 The consonants are interesting because they are numerous, show great variation in how they are produced and the signal is available for only the short time. They are "negative" because the voicing and vowel are interrupted or blocked by the position of tongue. Here I am going to use somewhat non-standard terminology and classification only because that is how I understand it. Also because i was introduced to the subject via Sanskrit Grammar.
There are three main things to look for - (A) Properties of original sound that is obstructed (B) manner in which the air flow is obstructed/modified
(C) place of obstruction/modification

Properties of original sound

  1. Voiced vs Unvoiced - whether voicing continues or not . [b -p]. [k -g][t-d] are some examples . (saghosh and aghosh.सघोष- अघोष )
  2. Aspirated vs Non aspirated - this difference is important in Indic langauges it effectively doubles the consonants available for use in languages.   (alpa prana- maha prana अल्पप्राण- महाप्राण)

Manner in which flow is obstructed /Modified

  1.  Stops - The airflow completely stops
  2. Friction - Sound produced by friction is introduced in the mix.
  3. Affricates - these are combination of stop, followed by the friction at the same place.
  4. Liquids - sibilant and approximants - where air flow is partially blocked
  5. Nasals - the airflow goes through the nasal channel


Place of articulation

  • Labial 
    • Bilabial
    • Labio-dental
  • Coronal 
    • Dental
    • Alveolar
  • Palatal 
    • Alveo-palatal
    • Retroflex
    • Palatal
  • Dorsal
    • Velar
    • Uvular 
  • Radial 
    • Pharyngeal /Epiglotal
    • Glotal

Edited from original here : http://en.wikipedia.org/wiki/File:IPA_chart_2005_png.svg

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