Of such a doubled sound-imitation word, to which the affix ā is added which causes elision of the final at , for the final t of the first member and the initial consonant of the second member, such subsequent consonant is always the single substitute.,
Thus पटपटा करोति 5.4.57, दमदमा करोति ॥ पटत्पटत् + डाच् 5.4.57 = पटत्पटा = पटपटा (त् + प् = प्) ॥ This sutra is really a Vartika. When the affix डाच् 5.4.57 is added to पटत्, there is doubling of the word by the Vartika under 8.1.12: this doubling takes place before the final अत् is elided.,