43 dB noise level from speaker with amps (not including pre-amp)

Do you hear noise from the listening position? 

Decibels are logarithmic, not linear. If the noise floor is 45 dB and you add another 45 dB from your speakers, the combined dB is 48. If you double the noise and add 90 dB to the ambient, the combined level is 90.00014. The numbers to the right of the decimal is the ambient contribution, which is essentially zero.

The formula for adding two decibels dB1 and dB2 is 10 x Log [10^(dB1/10) + 10^(dB2/10) ]

What dB meter are you using and has it been calibrated to a known standard? If you’re going to mention a specific dB level it should have been calibrated to NIST

Ho do you calibrate an iPhone app....LOL

Thank you all!

1.  I am using a basic dB app.Decibel X.on iPhone   Any other suggestions?  I realize it is not NIST and not calibrated.  Nice toy.

2.  App is helpful.  I compared impact by moving the tonearm pump to another room.  Dropped 7 to 8 dB.

Forgot about the logs.  Great.  Now I see - totally unimportant!!  Very helpful.  I was worried my tube amps had to high noise when they are turned on.

Thank you.