Originally Posted by LotI
Originally Posted by eljefino
The crummy ones block 29 dB and the good ones 32. Hardly a difference.
That's double the sound energy, a significant difference. Every 3dB is a doubling(or halving) of energy and 10dB is 10x. 20dB is 100x. Log base 10.
The decibel scale is an arbitrary scale based on human hearing, named after Alexander Graham Bell. 0dB is absolute silence, 1dB would be a mosquito flying 3 meters away from you in that silence, if you had perfect hearing like a10 year old boy.
You got it. Human hearing's sense of loudness behaves not on a linear scale but on a logarithm scale. That 3 dB (intensity level) difference represents a doubling (or halving) of the total sound energy that reaches your eardrum. That's especially important when dealing with very loud sounds that damage the inner ear if presented long enough (ex., in industrial work, very loud concerts, etc). A 3 dB improvement in ear plug efficiency can allow its wearer to safely endure very loud sounds by twice as long without damaging his inner ear (cochlea).
But eljefino is also correct. In the sense that 3 dB is hardly significant in terms of LOUDNESS PERCEIVED. Because growth in perceived loudness follows a logarithm curve. In fact, many people can hardly tell the loudness difference between two sounds of the same frequency that differ in intensity by 3 dB.
And, oh, just a bit of fact. 0 dB is not absolute silence. It just means that a sound of 0 dB is the average threshold of human hearing, the softest sound a normal ear can just detect. Many audiometers (electronic machines used to test hearing sensitivity) generate -5 and -10 dB test sounds(softer than 0 dB) for the occasional person who happens to have a wee bit better hearing than the rest of us.