Sound Pressure (Pa) Chart! Measuring Sound Pressure The chart below shows the sound pressure level decibel scale compared to the sound pressure Pascal scale.ĭownload and print Sound Pressure Level (dB) vs. P ref = 2 10 -5 - reference sound pressure (Pa)ĭoubling sound pressure (in Pa) - increases sound pressure level (in dB) with 6 dB(or 20 log (2)). Since the energy in the sound wave is proportional to the square of the pressure - the Sound Pressure Level in decibel can be expressed as: This minimum audible level occurs normally between 30 Hz.įor a normal human ear pain is experienced at a sound pressure of order 60 Pa or 6 10 -4 atmospheres.ĭue to this range it is convenient to express sound pressure with a logarithmic decibel scale related typically to the lowest human hearable sound - 2 10 -5 Pa or 0 dB. The lowest sound pressure possible to hear is approximately 2 10 -5 Pa (20 micro Pascal, 0.02 mPa) or 2 ten billionths of an atmosphere. (Similarly, electrical power goes as the square of the voltage.) The log of the square of x is just 2 log x, so this introduces a factor of 2 when we convert to decibels for pressures. The power in a sound wave goes as the square of the pressure. Sound is usually measured with microphones responding proportionally to the sound pressure. the SI-unit for sound pressure is Pa or N/m 2.Sound Pressure is the sound force ( N) acting on the surface area ( m 2) perpendicular to the direction of the sound.

Sound decibels scale