Sound Intensity and Threshold of hearing

[gomess]

My textbook says that in the equation β= 10log(I1/I2), I1 in most cases is the threshold of hearing (1.0x10^-12). Just out of curiosity, when is I1 not the threshold of hearing?

 

[lightgrav]

the reference intensity for zero dB, is 1 pico-Watt/m^2 . I can't hear such faint sounds anymore, especially at the edges of my frequency range. I used to be able to hear 1/8 picoWatt/m^2 ... that's -9 dB ... at 880 Hz.

 

[BenG549]

My textbook says that in the equation β= 10log(I1/I2), I1 in most cases is the threshold of hearing (1.0x10^-12). Just out of curiosity, when is I1 not the threshold of hearing?

Well sound intensity is the measure of a ratio of two sound intensities, when we are discussing the sound intensity experienced by people, then it is useful to set this 'reference' level at the average threshold of human hearing. In any situation when you are not concerned with sound intensity as experienced by people, you might choose a different reference level, it would depend on what you wanted to measure.

 

[gomess]

Oh okay, i see that makes more sense. I was always wondering why we placed that value as I1, there seemed to be no explanation from my book, it simply stated to do so