40 decibels is whispering in the ear. People's hearing is dull. If they don't pay attention, they can't hear it. It is extremely tiny and even ignored. Decibel range size reference: 0 ~ 20 decibels, very quiet, almost imperceptible. 20-40 decibels is about whispering in the ear. 40-60 decibels belong to our normal conversation voice. Above 60 decibels, it belongs to the noisy range. We can think that 70 decibels is very noisy. And began to damage the auditory nerve. Above 90 decibels will lead to hearing loss. While staying in the space of 100- 120 decibels, people will be temporarily deaf (deaf) for one minute unless there is an accident.