Sanskrit: Visarga Sandhi

aspiration or voiceless breath: /h/

When this breath passes though, if you manipulate your tongue in a certain way, you can produce different fricatives. If you lift the back of your tongue up and bring it closer to velar area, that breath /h/ becomes a velar fricative /x/. If you move the tongue position to the front, it can become a sibilant.


That's what happening in Sanskrit. 99.9 percent of sanskrit learners have no training in practical phonetics; sure, their training is theoretical phonetics without kinesthesia.

1. voiceless:

h + dental/retroflex t > dental/retroflex s (fricative)
h + palatal affricate   > palatal s (fricative)

2. Since Sanskrit does not have labial and velar fricatives,

h + k > hk
h + p > hp

3. voiced consonants:

aah + voiced cons >  aa + voiced cons


4. ah + voiced consonant > o + voiced con
5. ah + V - {a} > a +  V - {a}
6. ah + a > o
7. Heavily used combinations

sah (that) + any cons > sa
esah  (this) + any cons > esa

Notice one thing, though: ah + a > o, aah + voiced > aa + voiced.

Here, it shows that a and aa have qualitative differences: a is higher than aa in the vowel space.

http://www.cs.uky.edu/~gstump/520/2005_520_lesson_3c_4b_handout.pdf