[Chris2828]

I was playing billard a few times and noticed that the balls actually make very loud sounds when they hit each other. Billard balls can make noises of 90db. I did not experience directly a bad feeling in my head from those sounds but it is known that the sound waves of a loud noise are not good for the brain. So my question is more a general one. How bad are loud sounds for the brain, without directly feeling pain?

[Mark in Idaho]

The very short period of peak sound should not be a problem.

The intensity of the sound decreases at the inverse square of the distance. If the sound at 1 foot is 90 dB, at 3 feet, the sound will be 1/9th as intense. Put another way, for every doubling of the distance, the intensity of the sound decreases by 75%. dB values are not a straight line so you can not subtract 75% from 90 dB to get the sound at 2 feet.

Unless the sound is from the ball hitting your head, it should not be a problem. If you are sensitive to the sound, wear ear plugs. Some billiard players do.

Something to remember is this. The research suggests that the brain is tolerant of very high impact forces if those forces are for a very short period. The sound of billiard balls colliding lasts just milliseconds.

[Chris2828]

Thanks mark for your good explanation. So that means that standing near a mower for a few seconds is much more a problem than billard balls hitting together? Then why does one usually not feel the lonlasting sound compared to the short ones? I noticed that the billard balls can cause a bit of pain inside the ear(not necessarily the brain) when they hit very hard. I never experienced something like that with a mower.

Well I would say that I am overall very sound sensitive. The idea with the ear plugs was the next thing I wasvplanning to do.

[Mark in Idaho]

The difference could be that the billiard balls spike sharply where the mower is more continuous and has a gradual buildup of intensity. Foam ear plugs are good at knocking down the peaks.

[Chris2828]

It is certainly the short peak that causes the pain. But it is difficult to understand why this should be less harmful for the brain. The pain or unpleasant feeling occurs only in the ear, I don't know how far the sound waves go up to the brain.

I believe you, when you say that longer high db's are more harmful for the brain. But it is difficult to understand it

[Mark in Idaho]

The ear drum is a thin membrane that is designed to move with the slightest energy transmitted through/by the air. The brain and skull have much more mass and support structure that holds everything in place. Moving air will not impact the skull/brain.

I did not say that longer dB's are more damaging to the brain. Longer impact forces are. dB's are not really impact forces. They are vibratory forces in the air. The air moves back and forth very short distances. Air can easily move the thin membrane of the ear drum. It takes far more energy to move the skull and/or brain matter.

The ear drum has a mass similar to paper. It does not take much force to move paper. But, you could not flap a piece of paper at the skull and cause any impact to the skull. Sound travels at about 1100 feet per second. For air to transmit enough force to cause damage, the shock wave would need to travel much faster or have far more energy (dBs). 90 dB's does not even hurt the paper thin ear drum unless it is sustained over long periods where it can cause scaring/stiffening/thickening of the ear drum.

Without a basic understanding or weight and motion physics, I doubt you will understand these issues. Just try to believe me when I say the sound of billiard balls hitting does not injure the brain.

[Chris2828]

Well this explanation was good enough to get a good understanding of the difference.

Thanks a lot