From: blockedofcourse@foo.invalid   
      
   On 12/11/2025 4:05 AM, John R Walliker wrote:   
   > They may claim 300dB but I don't believe it.   
      
   It's a consumer device marketed to consumers.  Not a scientific   
   device or even an industrial device.  "Someone" determines   
   what THAT audience wants to consider as an appropriate   
   "standard" for their devices.  Then, the salesmen get involved.   
      
   >  There are several   
   > problems.  They don't specify whether this is a sound pressure   
   > level, in which case they need to specify the distance at which   
   > the measurement was made or whether it is the total sound power   
   > integrated over all directions.   
   > Sound pressure level has a reference level of 20 micro Pascal   
   > Sound power level has a reference level of 1 nano Watt   
   >   
   > The following document gives an interesting perspective:   
   >   
   > https://ntrs.nasa.gov/citations/20120003777   
   > "the largest sound power levels ever experienced at NASA Stennis   
   > was approximately 204dB, which corresponded to the Saturn S‐IC   
   > stage on the B‐2 test stand."   
   >   
   > At a distance of 1m with the sound radiating equally in all directions   
   > the numerical value of the sound pressure level is about 11dB lower   
   > than the sound power level.  At a distance of 28cm they are   
   > numerically equal.   
      
   There is *no* mention of distance.  It's "bogounits" dressed up   
   in "sciencey" terminology.   
      
   A device advertised as X claims to be louder than one claiming   
   to be Y -- for X > Y.  The vendor only has to be wary of   
   someone stating that X !> Y to tarnish their reputation.   
   (Assuming people actually care about that assessment).   
      
   > Just suppose that the horn was measured at a distance of 28cm   
   > and that the measurement was of sound pressure level.   
      
   "Suppose" is the operative word.  You have no idea how they are   
   rationalizing/justifying their claims.   
      
   Elsewhere, this thread, I cited a device that makes specific   
   claims of SPL vs distance (typical use being severe weather alert).   
   127 dB at 30m.  87 dB at 3km (!)  I.e., ~165 dB at 1 ft.  What would   
   it be at the phase plug -- 200 dB?  And, that's a "respectible"   
   device (not consumer floobydust) marketed to government/industry   
   (that presumably would know how to interpret said data).   
      
   Yet, it is *still* conditioned -- "over flat terrain at a   
   specific frequency when driven with a specific power source".   
      
   If *it* was advertised as "200 dB", would you doubt their   
   claim (even though no one would realistically evaluate it   
   at 1 ft in a "weather alert system")?   
      
   > If the sound source was omnidirectional the sound power would   
   > be 300dB relative to a reference level of 1nW.   
   > This would be a power of about 10^21 W or about 1 trillion   
   > nuclear power stations.   
   >   
   > I stand buy my suggestion that the consequences would be   
   > apocalyptic!   
   >   
   > John   
   >   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)