“The phenomenon of multisensory perception can help us to understand why we assign metaphorical properties of softness, roughness or depth to voice. Think of a politician whose voice is flat. Flatness is a multisensory concept because it is both tactile and visual. We can recognise flat surfaces by either touching or seeing them. These sensory impressions inform us about the acoustic characteristics of voice, implying that it does not have variation in tone. Notably, flatness can also convey lack of sympathy and emotion on the part of the speaker.”