# Did the pressure unit “bar” change definitions since the 1930s?

I don't see anything in Wikipedia about it, but (from this question) when I try to reproduce the equations in this 1933 paper, I get values 106 away from the values in the paper. When I reproduce this equation, for instance:

I get 5×10−11 bar

Likewise, it says:

Sound intensity and pressure are related by acoustic impedance of air Z0 = 400 N·s/m3.

So

• I wonder how long it will take for "bars" as a unit of mobile phone signal strength to outweigh the unit of pressure in common usage? – Jonathan R Swift Mar 8 '18 at 9:07
• Or how many in the street... when going drinking :) – Solar Mike Mar 8 '18 at 10:42
• At STP 1 bar is 101325 pa if I remember correctly. – Solar Mike Mar 8 '18 at 10:42
• interestingly the "standard pressure" in STP actually varies by context, see en.wikipedia.org/wiki/…, it is 101325 or 100000 Pa depending on who you ask. In any case a bar is always 10^5 pa – agentp Mar 8 '18 at 22:22
• I think 1 bar = 100,000 Pa and 1 atm = 1.01325 bar = 101325 Pa – Ohio ChemE Mar 9 '18 at 1:27