# I Sound propagation with altitude/height

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1. Jul 8, 2017

### williamcarter

Let's say we have a 3 floor/level building , and someone is making noise outside, i.e: Playing guitar, given that all the building has the same sound isolation everywhere, what can you say about the sound propagation? we have 2 cases a) when windows opened b) when windows closed

Will the people living on 1st floor will be more affected by sound(will they hear it more intense), compared with the people living on 2nd floor, will there be any difference in terms of noise?

2. Jul 8, 2017

### phinds

Something to think about: If you toss a tennis ball at a first floor window and then at a second floor window, what factors go into how loud the resulting sound would be inside the two rooms?

3. Jul 8, 2017

### sophiecentaur

Is this a 1. A homework question or 2. Prelude to a legal case?
What do you already know about sound propagation in air and in solids?
PS are there any other large buildings nearby?

4. Jul 8, 2017

### williamcarter

The pressure/ force aplied, impedance I guess?

5. Jul 8, 2017

### williamcarter

It is just a thinking question I asked myself, no building nearby. I would have assumed that at 2nd floor the sound/noise should be less than at 1st floor. I thought as height increases(this case by 4 m) the sound usually propagates in the solid and it is reflected back, so it will take longer to propagate to greater heights/altitudes?

6. Jul 8, 2017

### phinds

I mean SPECIFICALLY. What is the action of the ball on each window? Hint: think about the normal force.

7. Jul 8, 2017

### williamcarter

I can think just about the pressure that is applied on the window, to hit the 2nd floor it would require more force in order to reach

8. Jul 8, 2017

### sophiecentaur

Where is this going? Are you comparing 'mgh' energy loss with 1/r2loss?
I am a bit confused by the OP. Are we being asked to help predict something or will he come up with an situation that is producing louder noise on floor 2 than on floor 1? It seems such a no-brainer to say the lower floor will get more via any route / mechanism that there has to be an evil catch to bring us crashing to the ground.

9. Jul 8, 2017

### williamcarter

My question was , given that we have a building in open air , isolated everywhere same , and an outside noise occuring, where will the noise have the biggest impact
a) 1st floor
b)2nd floor which is 4 m above 1st floor
c) it won t be any difference in noise

10. Jul 8, 2017

### phinds

and what do you think and why?

11. Jul 8, 2017

### sophiecentaur

That's very relevant. The distance of the source from the building would / could be relevant and also the temperature profile of the air around the building could have an effect. You can get refraction of sounds through air just as you can get it with light, although just 4m is not far.
I second phinds and would be interested to know what your ideas are about the subject.

12. Jul 9, 2017

### williamcarter

It won't be any difference in noise between the 2 floors/levels right?

13. Jul 9, 2017

### williamcarter

The distance from the building let's say about 3-4 meters , temperature constant at like 20 degrees Celsius, building not surrounded by anything, but has same phonic isolation everywhere.

I think that there won't be any difference in noise between the 2 floors, so if someone is having a party on the ground floor, the 1st and 2nd floors will hear the same noise(no difference in the noise intensity between the 2 floors that are 4 m apart in height.)

14. Jul 9, 2017

### sophiecentaur

That is very close. Where is it positioned vertically? You need to specify the problem much more tightly if you expect to get an answer.
That is a very unlikely thing to happen. What about the fact that the sound has to travel through the thickness of two floors, as opposed to one thickness of floor? You need to think again about what's actually happening. Why not read a bit about techniques for sound proofing buildings? Google is full of links. It's only necessary to read one or two to find something appropriate for your level.

15. Jul 9, 2017

### williamcarter

Say about a distance of 10-12meters away from the building

Now you confused me, so you are saying the people on the first floor will be more affected than those on the 2nd floor?
I just want a detailed answer: If someone is having a party on the ground floor 10 meters away from the building, is it true that the people on 2nd floor will be less affected due to the greater thickness that the sound needs to go through?(2 levels of thickness) compared with 1?

How is it correct with regards to the noise(1st floor vs 2nd floor) ? What is the correct answer and why?

16. Jul 9, 2017

### davenn

that's incorrect the more floors/ceilings the sound travels through the more attenuated the sound will get
anyway, that is a different issue compared to an outside sound
Ignoring minor air pressure/temperature differences with height, and the building insulating being constant, there is
only one that that will affect the sound level ( assuming an Omni-direction sound source)

have you figured out what that is yet ?

17. Jul 9, 2017

### williamcarter

The sound was coming from the exterior not from the interior, was coming from outside the building, how will this affect the noise with regards to the 1st and 2nd floor? Will be there any difference?

18. Jul 9, 2017

### davenn

as I said, yes there will and assuming the things that I stated ... what is the only thing left that will affect the sound level at each location ?

19. Jul 9, 2017

### williamcarter

So the sound comes from outside the building, and it will get atenuated until it reaches 2nd floor right, I mean the people inside the building on the 2nd floor will hear less noise than those on the 1st floor right?But how exactly, and why? There are 4 meters between the 2 floors.

I can think just about temperature/pressure difference between the 2 floors, and obviously the height.

20. Jul 9, 2017

### davenn

as I said, the temp/press differences over that height are minor and not worth worrying about

what factor specifically does height play in it
if it is higher it is ___________ from the source, therefore the sound is more ___________

you fill in the blanks

21. Jul 9, 2017

### williamcarter

If it is higher is has a greater distance from the source, therefore the sound/noise is less.

But is it such a big difference given that there is 4m between the 2 floors?

When I said there will be less noise on 2nd floor , SophieCentaur laughed at me on post #8

22. Jul 9, 2017

### davenn

YES and it is more attenuated

naaa, by ear probably not noticeable ... but may be measured with sensitive sound meter

if you were to compare over a much further distance ... 10, 20 floors or more then you would start hearing a signif difference

23. Jul 9, 2017

### williamcarter

24. Jul 9, 2017

### davenn

that wasn't me ... I really don't know what he was getting at ???? don't worry about it

the bolded bit was the important part, for the reason you have now discovered

Dave

25. Jul 9, 2017

Thank you.