Change in sound intensity over distance

In summary, the problem involves two trains on parallel tracks, one approaching at a constant speed of 11 m/s and the other moving away at the same speed. Both trains are blowing horns with the same output power and frequency. The task is to calculate the time it takes for the sound intensity of the approaching train to increase by 2 dB at the observer's position, and the distance of the receding train when its sound intensity decreases by 6 dB. The equations used are I(r) = P_o/4∏r^2 and dB=10log(I/I0), but it is necessary to find a way to relate distance to change in decibels.
  • #1
titans2206
1
0

Homework Statement


You are standing in between two sets of railroad tracks. On one set of tracks a train is initially 200 m away and approaching you with a constant speed of v0 = 11 m/s. On the other set of tracks second train is at the same distance and moving away from you at the same constant velocity. Both trains are blowing their horns. The output power of each horn is the same and the frequency of each horn is 440 Hz. Take the velocity of sound in air to be vair = 343 m/s.

Calculate the time it will take for the sound intensity from the approaching train at your position to increase by 2 dB?

Calculate the distance of the receding train from your position when its sound intensity has decreased by 6 dB?

Homework Equations


I=P/4πr2
dB=10log(I/I0)

The Attempt at a Solution


Not really sure where to start, I do not know how to get dB into power so that I can use the first equation. Once I find the distance I know how to find the time, but I am having trouble relating distance to change in decibels.
 
Physics news on Phys.org
  • #2
Start with I(r) = P_o/4∏r^2

I0 = I_o = I(r_o) = P_o/4∏r_o^2

now use dB=10log(I/I0)

?
 

FAQ: Change in sound intensity over distance

What is sound intensity?

Sound intensity is a measure of the energy of sound waves per unit area. It is typically measured in decibels (dB) and is related to the loudness of a sound.

How does sound intensity change over distance?

As sound travels through a medium, it spreads out and becomes weaker with distance. This is due to the energy of the sound being dispersed over a larger area, resulting in a decrease in sound intensity.

What factors affect the change in sound intensity over distance?

The main factors that affect the change in sound intensity over distance include the type of medium the sound is traveling through, the frequency of the sound, and any obstacles or barriers that the sound waves encounter.

How is the change in sound intensity over distance calculated?

The change in sound intensity over distance can be calculated using the inverse square law, which states that the intensity of sound is inversely proportional to the square of the distance from the source.

Why is understanding the change in sound intensity over distance important?

Understanding the change in sound intensity over distance is important in a variety of fields, including acoustics, engineering, and environmental science. It allows us to predict how sound will behave in different environments and how it may impact human health and the environment.

Similar threads

Waves: Calculate the sound intensity from two speakers
Replies
3
Views
2K
Sound intensity of a thunderbolt
Replies
1
Views
1K
Calculation for finding distance with regard to sound intensity
Replies
18
Views
2K
Calculating Intensities of Out-of-Phase Sound Waves
Replies
1
Views
2K
Sound Intensity (Level) - Hearing Aid
Replies
5
Views
2K
Calculating Sound Intensity and Pressure Variation at a Distance
Replies
4
Views
1K
Calculating τ by knowing I is proportional to A^2
Replies
8
Views
2K
What is the decibel level of a sound at 4% intensity of a 95dB sound?
Replies
2
Views
2K
"Sound Intensity Decreases with Distance
Replies
5
Views
2K
How Does Distance and Quantity Affect Sound Intensity?
Replies
1
Views
3K

Hot Threads

Recent Insights

Back
Top