How can I calculate audio dB level?

Question

I want to calculate room noise level with the computer\'s microphone. I record noise as an audio file, but how can I calculate the noise dB level?

I don\'t know how

Answer 1

I use a sound level calibrator. It produces 94 dB or 114dB at 1 KHz wich is a frecuency where weighting filters share the same level. With calibrator at 114dB I adjust mic gain to reach almost full scale input simply watching a sound card based virtual osciloscope. Now I know Vref @ 114dB. I developed a simple software based SPL meter that can be provided if needed. You can use REW too. You hace to know that PC hardware hardly reaches 60 dB of dynamic range so calibrating @114 dB it wont read less than 54dB, wich is pretty high if you consider that sleeping is good with less than 35 dB A. In this case you can calibrate at 94dB and then you may measure down to 34dB but again you will hit pc and mic self noise wich may you prevent to reach such low levels. Anyway, once calibrated, measures at 114dB and 94dB should read fine. Note: the lab standard pistonphone calibrator operates at 250 Hz.