How loud is a scream?

A siren at 30 ft distance can have a sound pressure level of L = 130 dBSPL.

Never forget to tell the distance of the measuring microphone from the sound source, because the closer you are the louder it is.

The sound pressure level decreases by 6 dB per doubling of distance from the source to 1/2 (50 %) of the sound pressure initial value.

The sound pressure decreases inversely as the distance increases with 1/r from the sound source.