From: jrwalliker@gmail.com   
      
   On 11/12/2025 11:57, Don Y wrote:   
   > 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")?   
      
   That device would produce a sound pressure level of about 167dBspl   
   at 30cm from the source.   
   I would certainly doubt a claim of 200dB.   
   John   
      
   >> 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)