How can I calculate the sound pressure level at a known distance from the PA?
Sound intensity reduces rapidly in intensity at a distance from the source according to the inverse square law, which predicts that a doubling of distance will result in a reduction of ΒΌ the original, equal to a drop of 6dB, providing there are no reflections or reverberation. For example, in an open space where the front seats are 6 meters (20 ft) from the sound source and the back seats are 60 m (200 ft) from the sound source, you would expect the sound pressure to drop by a factor of 100 (=20 decibels) between the front seats and the back seats. In a real world auditorium, this reduction is partially mitigated by the effects of reverberation in the distant field, and in the near field because the speaker looks more like a wall source than a point source. However in a real-world situation like an auditorium, this reduction is partially mitigated by the effects of reverberation in the distant field, and in the near field because the speaker looks more like a wall source than a point s
