The failure of hospital caregivers to respond to medical alerts is often attributed to “alarm fatigue.” Another possible explanation: alarms sounding simultaneously can blend together, making one or more of them inaudible. The phenomenon, known as masking, makes it difficult to differentiate alarms, including those that signal life-threatening emergencies. A research team is developing a computer-based tool — using the same principles as MP3 audio files — to identify these auditory blind spots.