Sound pressure level

Sound pressure level (SPL) or sound level L_p is calculated in decibels compared to a reference sound pressure.

<math>

L_p=20\, \log_{10}\left(\frac{p_1}{p_0}\right)=10\, \log_{10}\left(\frac{p_1^2}{p_0^2}\right) \mbox{dBSPL} <math>

The reference sound pressure is

<math>p_0 = 2 \cdot 10^{-5} \mathrm{Pa}

<math>

= 20 µPa (micropascal), (Pa = pascal = N / m²; N = newton)

It can be useful to express sound pressure in this way when dealing with hearing, as the perceived loudness of a sound correlates roughly logarithmically to its sound pressure. Even the microphones work this way and our eardrums. They cannot convert the sound intensity.

See also

• Acoustics
• Sone
• Weber-Fechner Law