Decibel boundaries. Zero decibels is the threshold of human hearing; that is, 0 dB is the minimum sound level an average listener can hear when no other sound is present. At 120 to 140 decibels, sound pressure is great enough to cause our ears to begin to hurt. So nearly all sounds we typically encounter fall between 0 and 120 decibels. We can even narrow that range down a bit.
For everyday purposes, a bedroom will typically be in the 35-45 decibel range and a typical office environment will be around 45 to 55 decibels. When we speak to each other from arms' length away, we hear about 60 decibels. When we shout at each other from arms length away, the level jumps up to 80 or 90 decibels.
In terms of "how loud," sound levels at or greater than about 85 decibels, such as a lawnmower when mowing, are considered loud. Sound levels of 100 decibels or more are very loud, can feel unpleasant, and can cause hearing damage in less than 1 hour of exposure. Typical amplified music concerts are typically over 100 decibels and can reach 120 decibels or more.