QUIZ: A single sound source has a sound intensity level of 45 decibels at 11.3 metres from the source. In answering the questions below, assume the speed of sound in air is v = 331.3 m/s and that the density of air is constant at p = 1.29 kg/m . Also assume no loss in power over distance. The pressure amplitude is (mind the units): mPa (milli-Pascals). If the frequency of the sound is 600, the displacement amplitude of air particles is (mind the units): nm (nano-metres). If the power output of the source is multiplied 7 times, the new sound intensity level at 11.3 metres would be: db. Now that the power output has increased, the distance from the source at which the sound intensity level would again be 45 decibels is: m