The intensity of the soundwave is interpreted by the ears as its loudness. Weakest soundwaves which the human can hear has the value of 1x10^(-12) watt/m^2 and is called threshold of human hearing, Io. To compare relative sound intensity we use the scale called decibal, dB, that is computed witht formula dB=10log(10)I/Io, in formula, threshold of human hearing would have the dB reading of 0dB. As the result of installation of noise suppression materials, noise level in the auditorium was decreased from 93dB to 80dB. What percent decrease in intensity level of noise is due to installation of the materials?