If the level of noise from the two different time measuring less than 10 decibels. Shows whether the audio from other sources affect the volume while the machine is working.
If the noise level by measuring the time difference of less than 10 decibels of sound suggests that other sources used to work as a result of volume increases.
If a loud volume measurement of both times different than 10 decibels. That sounds from another source affects the volume while machinery work increased.