We won't go too heavy on the science answering this one!
dB (decibels) is a common unit of sound/noise measurement. The (A) part of it is a weighting to adjust for the relative loudness perceived by the human ear. Our ears are less sensitive to lower frequencies so a calculation is made to adjust for that....Yawn
Anyway, hears the cooler stuff to know
Examples of noise levels:
Breathing -> 10 dB(A)
Ambient noise in a Restaurant -> 60 dB(A)
A standard road car driving past you -> 70 dB(A)
Owen's laugh in our office -> 75 dB(A)
Food Blender -> 80 dB(A)
Typical track day noise limit -> 98 to 105 dB(A)
Live Rock Concert -> 108 - 114 dB(A)
Fighter Jet taking off -> 130 db(A)
Saying goodbye to your eardrums -> 150 db(A)+
The difference between 60 and 70 db(A) would feel twice as loud to the human ear, the scale is like a curve.
The average human threshold is around 110 db(A) but you can suffer damage at noise levels lower than that if exposed to them for a sustained period. You should be safe on a track day unless you spend all day spectating on track side. Always best to wear ear defenders anywhere you go where there is sustained loud noise.
Don't quote us on any of this, we found it on google!