structural:expansion, linguistic:voice_change
Lyapunov CLT

1 s n ∑ i = 1 n (X i − μ i) ⟶ d N (0, 1). {\displaystyle {\frac {1}{s_{n}}}\,\sum _{i=1}^{n}\left(X_{i}-\mu _{i}\right)\mathrel {\overset {d}{\longrightarrow }} {\mathcal {N}}(0,1).}