I remember some of our more seasoned pilots telling me that when we first got ACARS in the RJ, it would have an aural alert (something to the effect of "Incoming Message"). They said it became too distracting, so they disabled it. When we get a message, all we get is a line in the scratchpad of the FMS letting us know. If we have a single FMS aircraft, it's really hard to keep looking down for messages. The "data chirps" in our headset is really the only way we know to look.