The suffix applied तृतीया-ending समर्थ stars(constellation)-indicating श्रवण अश्वत्थ प्रतिपादिक (with time context) undergoes लुप् in noun. For example, श्रवणेन युक्ता रात्रिः (4.2.4 would bar लुप् but it is allowed through the current sutra) - श्रवण् टाप् - श्रवणा.