Public mathematics with help from Jo.

[apiphile]

5. Calculate the pressure amplitudes for SPL readings of 26dB and 20dB. How are the two pressure amplitudes related?

dB = 20log (input/ref)

Part 1:

26 / 20 = 1.3

log(ref) = -4.698970

1.3 + -4.698970 = -3.39897

10^-3.39897 = 3.990524
3.990524 N/m^2 which is basically 4 N/m^2

which doesn't make any sense at all because 56dB came out as less Newtons per

Comments

[thegreatgonzo]

Does this help any: http://www.sengpielaudio.com/calculator-soundlevel.htm

[apiphile]

I'm supposed to do it the hard way. :(

[kalorlo]

I got the answer for part 1 to be 0.00039905246698. But I don't know what units go where. Are you given the log(ref) as a standard?

[apiphile]

I think I am clearly doing something assbackward but I don't know what. And yes, the log(ref) is based on the universally accepted threshold of hearing, which is 20μN/m^2.

[kalorlo]

I just plugged the numbers in to the scientific calculator at http://web2.0calc.com/. You seem to be losing decimal places. I mean, what I've written is the same as 3.993x10^-4. Is your calculator saying that? Would explain your tweet about those numbers both coming out the same.

[kalorlo]

Whoops, I mean 3.9905x10^-4... The same number as I said above, but you count what place the 3 is after the decimal point and write it as an exponent so you don't have to write out all the zeroes.

[faeries_bite]

Logs make me D: