1975: Margaret Thatcher worked hard to improve her public speaking skills. Analysis of recordings showed that over a decade she succeeded in lowering the pitch of her voice by about 60 hertz, which made her sound more assertive, gave her more gravitas. She had less success with the tone of her voice. Even at the end of her political career it still sounded (to use Clive James’s description) like a “condescending explanatory whine” that treated the person on the receiving end as if they were “an eight-year-old child with personality deficiencies”.
Source: Anne Karpf, The Human Voice: The Story of a Remarkable Talent (2006), pp. 226–9