My parents are listening to 70s music downstairs and I can hear the drums and basslines but not anything else unless I open the door.
In: Biology
Lots of things going on here, but here’s a major reason why this is the case.
Speaker sound is electrical energy converted to air pressure waves that pulse. These pulses hit your ear drum. Your ear drum moves as the result of the air pulsing against it. Your brain converts those pulses into electrical energy and you hear the sound.
As these pulses hit a wall, the wall shakes back and forth just like your ear drum. A 50hz bass frequency wave has a length of about 22.5 feet, much longer than the thickness of the wall, so the wall has plenty of time to physically move back and forth to reproduce that sound on the other side (that you hear from upstairs). But because there’s a lot of mass in the wall that absorbs some of the energy, the sound isn’t reproduced with much fidelity.
A high frequency wave, on the other hand, can have a much shorter length than the thickness of a 4 inch wall. And when it hits the wall, the wall isn’t able to cycle back and forth before the next wave hits. So the waves lose their energy against the wall before they can go through it.
As I said, lots of other things going on here, but this is the main reason why thicker, heavier walls don’t allow as much sound to propagate through them as thinner, lighter ones. And why in all cases higher frequencies will attenuate more than than lower ones.
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