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In all the houses of two levels where I have been, why I hear the sound from downstairs clearer when I am at the second level, than I hear sound from upstairs when I am at the first level?

Does sound travel upward more easily than downward?

Do the architectures of houses matter much?

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What rooms have you been in to test this? It is not a controlled environment if the material of the walls or flooring is different or the size of the room is different. The acoustics will all change depending on this, the same reason why music tends to (in my opinion) sound better when played in the bathroom - there tends to be tiling which reflects sound a lot better than carpet or wallpaper. –  Carterini Mar 3 at 18:32
    
I am in bed rooms upstairs, while some people are talking over the phone in living rooms downstairs, which is distracting. –  Tim Mar 3 at 18:47
    
Have you considered the possibility that you're imagining it? When you're in your bedroom, you're expecting no sound, so any sound seems loud. When you're downstairs in the living room, you don't really care so you ignore any sound that you would have felt loud in your bedroom –  Pranav Hosangadi Mar 3 at 21:01
    
@PranavHosangadi: I don't believe I am imagining it. –  Tim Mar 3 at 22:00

2 Answers 2

This is an interesting question. I regret that I don't know the answer for sure, but I can say that sound does not travels in any substantially different way upwards vs downwards. Rather, I believe the answer has to do with the fact that low frequencies are carried through the physical structure differently because of where they are: things that make sound tend to be in physical contact with the floor, not the ceiling, and that physical contact carries extra low-frequencies.

Imagine a stereo: it is physically connected to the floor (perhaps through a bookshelf) which conducts the low frequencies downstairs, and creates a muddy sound. Upstairs, however, they don't get those additional low frequencies, just the air->ceiling->air sound, so it's a bit clearer (albeit quieter).

The same logic would apply to children running, furniture moving, and even people speaking.

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To add I think there will be some variation in the volume of the sound relative to upstairs or downstairs if the medium (ceiling) is not equidistant from the point of hearing and the point of production. So if you are closer to the medium more of the initial sound will pass through to the next room than if you are further away from it as it has more room to disperse. –  Carterini Mar 3 at 19:11
    
I think you may be onto something but your logic may be slightly off. Are things upstairs not just as likely to be attached to the floor and so have the same effect? I think @Carterini may be closer to the correct effect. –  nivag May 8 at 15:59

I have a theory. Since the first floor is anchored to the ground and is likely concrete, both act as a buffer. Imagine a speaker playing music. Now touch the speaker. The level decreases dramatically. Think of your finger as earth. It more mass than the speaker cone. It has more potential energy than the speaker has kinetic energy, thus drastic attenuation.

Now the second floor is only anchored to the first floor. This would be similar to adding a second speaker cone to the first cone. Since the mass of the second cone is close to the first, very little attenuation occurs.

Have you noticed the same effect on a pier and beam house?

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