==liên kết ngoài==*sound pressure and sound power  effect and cause*conversion of sound pressure to sound pressure level and vice versa*table of sound levels  corresponding sound pressure and sound intensity*ohm's law as acoustic equivalent  calculations*definition of sound pressure level*a table of spl values*relationships of acoustic quantities associated with a plane progressive acoustic sound wave  pdf*sound pressure and sound power  two commonly confused characteristics of sound*how many decibels is twice as loud