OT: math problem with acoustics?

If: a) The threshold of human hearing is one micro bar = one atmosphere /

1,000,000 = 0 db re u bar b) The max amplitude of a sound wave conducted by air would be a vacuum in the trough and 2 atmospheres at the peak

Then the max amplitude sound wave would be 20 log 2,000,000 = 126 db

How do they get 130 db?

Is it a square wave with root[2] = 1.414 => 129 db?

Thanks in advance

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The reference pressure level of 0 db acoustic is .0002 dyn/ cm^2 (.0002 dynes per square centimeter) or also 20 microPascals

1 atmosphere at sea level is 101300 N/ m^2 (101300 Newtons per square meter).

Pressure measured in dynes= 20 log(( X dyn/cm^2)/(.0002 dyn/cm^2)) , therefore 20 log (101300/.00002) = 194 db

and 194 db acoustic is when sound turns into clipped square waves, such as the space shuttle take off noise.

cheers T.Alan

As others have noted, the reference is not one microbar.

Nor is the limit 2 atmospheres (30 psi). To take an extreme example, explosions easily exceed this.

Joe Gwinn