A barking dog delivers about 1.0 mW of power, which is assumed to be

[chemistrymole]

Homework Statement

A barking dog delivers about 1.0 mW of power, which is assumed to be uniformly distributed in all directions. What is the intensity level in decibels at a distance 5.00 m from the dog? The threshold of human hearing is 1.0 × 10-12 W/m2.

Homework Equations

I=P/A A is 4pi(r^2)

The Attempt at a Solution

The only part I am missing is converting the 1 mW to something else so I can plug in the equation above. I tried the 10*log(xxxxxxxx) formula no luck.

 

[berkeman]

Homework Statement

A barking dog delivers about 1.0 mW of power, which is assumed to be uniformly distributed in all directions. What is the intensity level in decibels at a distance 5.00 m from the dog? The threshold of human hearing is 1.0 × 10-12 W/m2.

Homework Equations

I=P/A A is 4pi(r^2)

The Attempt at a Solution

The only part I am missing is converting the 1 mW to something else so I can plug in the equation above. I tried the 10*log(xxxxxxxx) formula no luck.

Homework Statement

Homework Equations

The Attempt at a Solution

The power all goes through each spherical surface surrounding the dog. If the sphere has a surface area of 1m^2, then the power flux density is 1.0mW/m^2. If the sphere is a little bigger, and has a surface area of 2m^2, then the power flux density 1.0mW/2m^2 = 0.5mW/m^2.

Does that help?

 

[chemistrymole]

No still lost and confused.

Can someone please explain equations further I am not seeing how it connects to the variables given in the question.

 

[haruspex]

No still lost and confused.

Can someone please explain equations further I am not seeing how it connects to the variables given in the question.

As the sound waves of the bark radiate out from the dog, the 1mW of power (P) gets spread over a progressively larger area (A). At a distance of 5m, what area is it spread over?

 

[chemistrymole]

As the sound waves of the bark radiate out from the dog, the 1mW of power (P) gets spread over a progressively larger area (A). At a distance of 5m, what area is it spread over?

Do I have to convert 1 mW to W?

So would my setup be I = 1/pir^2?

I think my main formula template is I=P/A

 

[chemistrymole]

Thanks everyone I found a solution that shows me how to do it. Now I actually understand it and know how the units work.