Kahneman et al identify 3 types of noise.

1. Systematic noise caused by consistent biases in judgement. Like an engineer who always under-estimates Jira stories.
2. Interpersonal noise happens when different experts review the same data and come to different conclusions. Like when engineers disagree on a story estimate.
3. Situation noise describes how the same expert changes their judgement based on random situational factors. Like an engineer who under-estimates when they're excited and over-estimates when tired.