Äänenpainetaso

Äänenpainetaso is the Finnish term for sound pressure level, a physical quantity used to express the magnitude of sound waves. It is a logarithmic measure of the effective pressure of a sound relative to a reference value. The standard reference pressure in air is 20 micropascals, which is approximately the threshold of human hearing at 1 kHz.

Sound pressure level is measured in decibels (dB). A sound with a pressure of 20 Pa corresponds to a sound pressure level of 120 dB, a level that can cause pain. Higher sound pressure levels, such as those produced by jet engines or explosions, can cause permanent hearing damage. Conversely, very low sound pressure levels, like a quiet library, might be around 30-40 dB.

The logarithmic scale is used because the range of sound pressures that humans can perceive is very wide. A linear scale would be impractical for representing these differences. Äänenpainetaso takes into account both the amplitude of the sound wave and the sensitivity of human hearing. Different frequency weightings, such as A-weighting (dBA) and C-weighting (dBC), are often applied to sound pressure level measurements to better reflect how humans perceive loudness at different frequencies. A-weighting is most common for measuring environmental noise and workplace noise.