I don’t know, I this phrasing seems quite evocative to me. Tremble means to waver in tone or power, gravel means to hoarse or growling in a low energy fashion, and words colliding means for words to flow into one another in a fluid and informal way. This all makes speech sound less confident, and less educated. Meanwhile, neat speech is formal, and clipped speech has clear start and end points to words, and so clear distinctions between neighbouring words.