Mīmāmsa Sūtra 01.01.16

वर्णान्तरमविकारः ॥१-१-१६॥

varṇāntaram avikāraḥ ॥1-1-16॥

[वर्ण (varṇa) - sound; letter; color; class; अन्तरम् (antaram) - difference; distinction; interval; अविकारः (avikāraḥ) - absence of modification; unchanged state;]

The interval between sounds does not constitute a distortion (vikāra).