What visual cues are commonly used in comics to represent frozen speech style, such as robotic or monotonous voices?

Frozen speech is often depicted with jagged speech bubbles, straight lines instead of curves, rectangular or blocky text fonts, lack of variation in font size or weight, and sometimes the use of symbols or glyphs instead of letters to convey a non-human or emotionless tone. Solid, filled-in bubbles with no tails can also indicate a broadcast or pre-recorded message.