From: blockedofcourse@foo.invalid   
      
   On 12/10/2025 7:25 AM, Liz Tuddenham wrote:   
   > Martin Brown <'''newspam'''@nonad.co.uk> wrote:   
   >   
   > [...]   
   >>   
   >> ISTR that in the Three Mile Island disaster they spent the first fifteen   
   >> minutes of the emergency trying to silence all the different damn alarms   
   >> that made it impossible to think in the control room. Only once they had   
   >> the noise under control could they communicate with each other across   
   >> the room.   
   >   
   > I worked in a university where they had just one sounder for each floor,   
   > mounted at the end of a each corridor.  They had made it loud enough to   
   > be heard in the laboratories with all the doors shut.  It would have   
   > been safer to climb out of a window than enter the corridor and try to   
   > escape past the sounder.   
      
   You can get 200-300dB klaxon's relatively easily.  I had one in   
   college that was "fun" (for some perverse definition of "fun")   
   to play with.   
      
   Also had a large motorized siren out of an old police car.   
   Amazing how much current it required to spin the mechanism!   
      
   > When it went off one day, nobody could find out what was happening   
   > because communication was impossible.   
      
   Alarms/alerts should never be "solid" tones.  A cadence makes them   
   more noticeable AND gives you periods of relief between bursts.   
      
   There's a lot of research on "sirens" for emergency vehicles as,   
   there, localizing the source of the sound is important.  Observers   
   need more auditory clues than the naive sirens provide.   
      
   I have three compression driver horns outside the house (to   
   alert neighbors of a problem) and one inside the house (to alert   
   occupants).  Driving them with audio amplifiers (instead of fixed   
   frequency "tuned horns") gives you some variety in how you alert.   
      
   The problem with these things is *testing* them -- especially   
   "periodically"!   (hence the value of being able to dial back   
   the SPL)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)