Final answer:
The sound level of the airplane on takeoff, measured at 120 dB, is 1012 times greater than the threshold sound level, which is 10 dB. This comparison is based on the logarithmic relationship where each 10 dB increase corresponds to a tenfold increase in sound intensity.
Step-by-step explanation:
The threshold sound level is the minimum sound intensity that can be heard by the average human ear. In this case, the question states that the sound level of the airplane on takeoff is 120 dB. To determine how many times greater this is than the threshold sound level, we need to compare the two levels. According to the information provided, the threshold sound level is 10 dB, and each factor of 10 in intensity corresponds to a 10 dB difference. Therefore, the sound of the airplane on takeoff is 1012 times greater than the threshold sound level.