Function ratio_to_db 

pub fn ratio_to_db(ratio: f64) -> f64

pydub’s ratio_to_db in amplitude mode: 20 * log(ratio, 10), which CPython evaluates as log(ratio) / log(10) — not log10(ratio). 20 * log(2, 10) is 6.020599913279623; 20 * log10(2) is ...624.