What is Lenience on phonetics?

Answer 1

You probably mean "lenis" not "lenience." Lenis is the opposite of fortis, and refers to the relative amount of effort used in speech sound production. Sounds produced with more effort are said to have fortis, while sounds produced with relatively less effort are said to have lenis. Compare, for example, the amount of air exiting the oral cavity (mouth) on the speech sounds [p] and [b]. There is typically much more air on [p] than on [b], so we would say that [p] is a sound with fortis and [b] is a sound with lenis. For further explanation see page 45:

Bauman-Waengler, J. (2008). Articulatory and phonological impairments: a clinical focus (3nd ed.). Published by Allyn & Bacon, Needham Heights, MA. ISBN-13: 978-0-205-54925-2