Why did winston call katharine the human soundtrack?

Winston called Katharine the "human soundtrack" because she constantly spoke in a repetitive and mechanical manner, echoing the Party's slogans and ideologies without any genuine emotion or thought. Her dialogue was often devoid of personal insight, making her seem like a mere instrument of the Party's Propaganda. This characterization highlights the dehumanizing effects of totalitarianism, where individuality and authentic expression are suppressed.