Previous research has shown that urgent auditory warnings are likely to annoy drivers. Increased urgency could also raise drivers’ stress levels, which in turn could impact their ability to detect and react to subsequent changes in the traffic environment. We conducted a simulator experiment with 24 truck drivers to investigate the potential of urgent alarms to raise annoyance and negatively affect drivers’ subsequent responses to unrelated, critical events on the road. The drivers received two types of warnings that were designed to significantly differ in perceived urgency. Several times in the trial, an unexpected event occurred just seconds after drivers were presented with an unrelated warning, and the drivers had to brake immediately to avoid a collision. The results indicate that acoustic characteristics and semantic meaning may impact the perceived annoyance of in-vehicle warnings. Interestingly, we found a significant, negative correlation between the drivers’ experience (years of truck driving experience) and the rated annoyance for both types of warnings. Also, the drivers who received the high-urgency warning braked significantly harder and tended to brake later than the drivers who received a low-urgency warning. These results have implications for ITS systems for heavy vehicles that intend to implement auditory warning signals.