Physics, 31.12.2019 03:31 alexamorantess

Awoman stands a distance d from a loud motor that emits sound uniformly in all directions. the sound intensity at her position is an uncomfortable 3.9×10-3 w/m2. at a distance 3.8 times as far from the motor, what are (a) the sound intensity and (b) the sound intensity level relative to the threshold of hearing?

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From the general equations of sound we know that the Intensity is directly proportional to the square of the distance. Therefore the relationship,

$I \propto \frac{1}{r^2}$

It will help us find the change between the two points. If the relationship is maintained, the intensity of point one versus point two will be given by the square of the distance of the other two points, therefore

$\frac{I_2}{I_1} = \frac{r_1^2}{r_2^2}$

$I_2 = I_1 (\frac{r_1^2}{r_2^2})$

From the statement it is given that the distance is 3.8, therefore

r_2 = 3.8r_1

and

$I_1 = 3.9*10^{-3}W/m^2$

PART A) The intensity given under the previous equation found is

$I_2 = 3.9*10^{-3} (\frac{1}{3.8})^2$

I_2 = 0.00027W/m^2

Therefore the sound intensity at point 2 is 0.00027W/m^2

PART B) For the sound level in decibels we will apply the logarithmic equation that relates the intensities, therefore

$\beta = 10log_{10} (\frac{I}{I_0})$

Where I_0 is the threshold intensity and is given by

$I_0 = 10^{-12} W/m^2$

Then,

$\beta = 10log_{10} (\frac{0.00027}{10^{-12}})$

$\beta = 84.31dB$

Therefore the sound intensity level relative to the threshold of hearing is 84.31dB

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the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

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Awoman stands a distance d from a loud motor that emits sound uniformly in all directions. the sound...

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