Sound Intensity and Threshold of hearing

AI Thread Summary
The equation β= 10log(I1/I2) uses I1 as the threshold of hearing, typically set at 1.0x10^-12 W/m^2, which represents the reference intensity for zero dB. However, I1 can vary when measuring sound intensity not related to human perception, depending on the context of the measurement. The discussion highlights that while the threshold of hearing is a standard reference, different scenarios may require alternative reference levels. Personal experiences with hearing sensitivity, such as the ability to detect lower intensities at specific frequencies, illustrate the variability in human hearing. Understanding the rationale behind using I1 as the threshold of hearing clarifies its application in sound intensity measurements.
gomess
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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?
 
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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.
 
gomess said:
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.
 
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
 

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