To eliminate filler words (such as 'um'), completely empty your breath at the end of your sentences ('landing phrases') to force an inhalation, which physically blocks the emission of sound.

noli's read

Mechanically, the claim that one cannot say 'um' while inhaling is accurate: human phonation is an egressive process (during exhalation), a basic principle supported by the work of the Voice Foundation (expert opinion). Furthermore, research in behavioral science, notably a 2019 study by Montes et al. (observational), shows that training to use silent pauses effectively reduces verbal fillers. However, the idea of completely emptying your air at every sentence is exaggerated. Practitioners at the Buteyko Breathing Clinic (expert opinion) note, on the contrary, that speaking until out of breath can cause laryngeal tension, stress, and a noisy inhalation reflex. Finally, the specific 'landing phrases' technique and its associated calendar exercise have no direct scientific evidence and are based on the empirical method of a communication expert (opinion of Matt Abrahams, Stanford).

the sources

No named source held this one up — that absence is part of the verdict.