The correct answer is: A. 50 db to 70 db (decibel)
The decibel (dB) is a logarithmic unit that expresses the ratio of a physical quantity (such as sound pressure) to a reference value. The reference value for sound pressure is 20 micropascals (μPa), which is the threshold of human hearing.
Sound pressure
levels are typically measured in decibels (dB). The higher the dB level, the louder the sound. The following table shows some common sound pressure levels and their corresponding effects on humans:Sound pressure level (dB) | Effect on humans
———————– | ————————
0 dB | Threshold of hearing
20 dB | Very quiet whisper
30 dB | Quiet conversation
40 dB | Normal conversation
50 dB | Average office noise
60 dB | Noisy restaurant
70 dB | Vacuum cleaner
80 dB | Traffic noise
90 dB | Motorcycle
100 dB | Rock concert
110 dB | Chain saw
120 dB | Gunshot
130 dB | Painful to ears
140 dB | Instant damage to ears
As you can see, the ordinary and maximum tolerance limit of sound by human being is 50 db to 70 db. Exposure to sounds above 85 dB can cause permanent hearing loss.