How Do Sound Waves Travel Through Different Media?

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Homework Help Overview

The problem involves the propagation of sound waves through different media: air, fresh water, and a slender metal handrail, following an explosion at a pier. Participants are tasked with determining the order of arrival of sound through these media and the time differences between their arrivals.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the speeds of sound in each medium and attempt to calculate the time taken for sound to travel through each. Some question the interpretation of the problem regarding whether sound travels through the media in sequence or simultaneously.

Discussion Status

There is ongoing exploration of the timing calculations for sound arrival in each medium. Some participants have provided calculations for the arrival times, while others are questioning the assumptions made about the travel path of the sound waves.

Contextual Notes

Participants are navigating the implications of the problem's wording, particularly regarding the assumption of sound traveling through the media in parallel versus sequentially. There is also uncertainty about the accuracy of time calculations for the second sound's arrival.

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Homework Statement


An explosion occurs at the end of a pier. The sound reaches the other end of the pier by traveling through three media: air, fresh water, and a slender metal handrail. The speeds of sound in air, water, and the handrail are 343, 1482, and 5040 m/s, respectively. The sound travels a distance of 150 m in each medium.
(a) Through which medium does the sound arrive first, second, and third?

(b) After the first sound arrives, how much later do the second and third sounds arrive?

Homework Equations


v=sqrt(B/density)



The Attempt at a Solution



We just started going over waves and sound so I'm not sure how to figure out this problem.
For part (a) I figured out that the sounds arrives first at the steel handrail, then freshwater then air.
For part (b) I don't know how to figure that out. I tried just doing how many seconds it would take to travel 150m for each substance, but I don't think that's right.
 
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Well, the problem states the speed of sound in each medium, so you can get how long it takes in each medium using,

time = distance/velocity
 
So first it went through the steel handrail so that is 150/5040= 0.02976s, then through the water so 150/1432= 0.1047s, then the air so 150/343=0.4373s.
So the first sound happens after 0.03s, then the second sound comes after 0.1047s, then the third sound comes after 0.4373s. Right?
 
I get that the third sound comes 0.41s because you have to do 0.437-0.03, but I can't figure out how to get the second sound...?
 
The question asks how much later do the second and third arrive as compared to the first. You have done most of the work.
 
Well for the second I did 0.105-0.03 and it's incorrect...?
 
(a) Through which medium does the sound arrive first, second, and third?
This implies that the sound travels in parallel through the media, not through each in turn.
Otherwise it would always arrive in the last medium in the chain making the question meaningless.
 

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