When someone speaks in a monotone, his voice is flat and boring — plus listeners don't know how the speaker is feeling when everything sounds the same.

What causes a monotone voice?

This visual or verbal absent can be caused by conditions that include schizophrenia, autism, depression, and traumatic brain injury. Emotions to stimuli that are not expressed by people with flat affect include facial, voice and body language changes.

Is it bad to speak in monotone?

Speaking in a monotone voice is a real communication killer. When the variety of your voice's pitch doesn't vary, it's impossible for your listener to maintain any interest in what you're saying.