How Does Bass Shake a Room?

[chengbin]

I have a question. How does a bass shake a room? I went to my friend's house, who has a high end set up, and his subwoofer is ridiculous. The room felt like it is coming apart at high volumes. Other things I've felt is wall flexing and general room shaking. How does a little movement from a woofer does this to a room?

 

[Stonebridge]

I imagine that a number of things in the room have resonant frequencies that are close to the low frequencies put out by the sub-woofer.
For example, glass in the windows probably has a resonant frequency close to those of the bass in the music.

 

[chengbin]

I understand resonance as making something vibrate. But what I'm feeling is genuine shake. The walls feels like it is FLEXING.

Please correct me if I'm wrong.

 

[SpectraCat]

I understand resonance as making something vibrate. But what I'm feeling is genuine shake. The walls feels like it is FLEXING.

Please correct me if I'm wrong.

What is the difference between flexing/shaking and vibrating in your view? In mine they are the same. Think about a drum head, and how it moves when struck .. there are cool high-speed videos of these vibrations available on youtube.

 

[chengbin]

I define:

Flexing as ripples moving toward you (think of water hitting you on a beach)

Shaking as up and down movement, like a huge hand under the room moving up and down.

Vibrate as a very little shake, like what you get in a club.

 

[SpectraCat]

I define:

Flexing as ripples moving toward you (think of water hitting you on a beach)

Shaking as up and down movement, like a huge hand under the room moving up and down.

Vibrate as a very little shake, like what you get in a club.

Those are qualitative linguistic distinctions; physically they are all vibrations. Students in physics learn about 2-D harmonic modes of a vibrating drum head (which is equivalent to your "flexing" description) in their first or second year .. .there are analogous definitions for surface vibrations of 3-D objects as well.

The shaking you describe is also a vibration, since it describes motion of the system around a common center of mass, with no net translation.

In any case, each of these modes has a characteristic harmonic frequency that can certainly become resonant with the driving frequency from the bass sub-woofer. So I think such resonances are really is what is happening. That allows a lot of energy to be stored in these vibrational modes in a short amount of time.

 

[Stonebridge]

I would add that the low frequencies put out by the sub-woofers can also cause resonances in your body and its cavities - such as your chest. This can cause you to feel as though the room is moving when it may be that it's you! For example, your eyeballs/sockets can resonate causing you to imagine the room is moving.

 

[pallidin]

I would add that the low frequencies put out by the sub-woofers can also cause resonances in your body and its cavities - such as your chest. This can cause you to feel as though the room is moving when it may be that it's you! For example, your eyeballs/sockets can resonate causing you to imagine the room is moving.

Dang, you beat me to it! I was going to suggest something similar, as I have actually experienced that. I didn't know about the eyeballs though.
Of course, there IS room vibration as well.

 

[chengbin]

I would add that the low frequencies put out by the sub-woofers can also cause resonances in your body and its cavities - such as your chest. This can cause you to feel as though the room is moving when it may be that it's you! For example, your eyeballs/sockets can resonate causing you to imagine the room is moving.

That's an interesting point. You're probably right.