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I have a web application that monitors a service (polls) every 30 seconds or so, and displays any new records (notifications). Each one of these must be acknowledged by an operator. The customer has requested that these notifications also come with sounds (a single, non-looping sound clip, ~ 1 second each). Here is the UI: enter image description here

My question is: How should I handle multiple, simultaneous alarms? If the page refreshes data (ajax) and shows 3 new alarms, should the alarm sound be played for each alarm? I would think not. However, there is a requirement that each type of unit has its own alarm sound. In this case, would I play each different alarm sound, but at most once each?

Related, would it make sense to play for each alarm displayed, or only new alarms displayed? I.e., assume sounds have already played for the above alarms. Upon refresh, if these 3 alarms still exist, and there are no new alarms, would each sound (2 different) play again, or no alarms be played?

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How do these alarm sounds stop? Are they (for example) a 3 second sound-effect that plays once and that's it (such as a mobile phone text alert) or is it an alert that keep playing until the user comes and manually turns it off (as with an alarm clock)? –  JonW Apr 9 '13 at 15:01
    
@JonW Good question. They are single sound clips (< 1s each). I'll update my question. –  xdumaine Apr 9 '13 at 15:47
    
How unique and urgent is each alarm? Is it important that the user know Alarm 1 AND alarm 2 are going off, or is "alarms are going off" or "2 alarms are going off" sufficient? –  Ben Brocka Apr 9 '13 at 15:48

1 Answer 1

up vote 9 down vote accepted

The benefit of an audible alarm is that it gives the operator information without them having to look at the screen - and hopefully draws their attention to the screen. Each sound is also different to give the operator quick feedback on what the alarm is.

So when you have multiple simultaneous alarms, playing only one of the alarms would give misinformation to the operator. You should either:

  1. Play each audio alarm, one after the other. This should preferably be with a short pause between them (about 1 second) so that each alarm sound is distinct. To cope with situations where there may be 100 alarms, there should be a button on the screen (or keyboard shortcut) that will mute the remaining alarms.

  2. Have an alarm sound that indicates that there is more than one alarm (say a longer beep). Something unique that will not be confused with the other alarm sounds. This way, you will only ever have one alarm sound at a time. But by having the combo alarm sound, you lose some of the audio information that would be given by multiple distinct alarms.

I would recommend option 1 if you mostly have only 1 or 2 alarms at a time, and option 2 if you regularly have many alarms sound at a time.


These are the methods used in many safety control rooms in industrial plants, so they have been proven to work well already.

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+1 for referring to existing industrial control room practice. –  PhillipW Apr 9 '13 at 16:33

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