dBSPL

dBSPL represents a value of sound level expressed on a logarithmic scale, converting the pressure of the sound into dB. Through this, we can express the intensity and magnitude of the sound as perceived by humans.
Sound arises from the change in air pressure due to molecular motion, and this change in pressure is referred to as Sound Pressure. Sound propagates in the form of waves, where the magnitude of the sound is determined by the intensity of the pressure.

The logarithmic scale used in dBSPL is useful for representing the relative size of sounds. Using a logarithmic scale makes it easy to represent even when the range of sound levels is broad. This scale reflects the perceptual properties of sound and assists the human auditory system to distinguish between a wide range of sound levels.

The formula for dBSPL is as follows: dBSPL = 20 * log10(P / Pref)
Where P represents the pressure of the measured sound, and Pref is the Reference Pressure.

Pref is set to 20 micropascals (μPa). Typically, this is based on the minimum audible sound pressure at 1kHz, which is about 0.00002 times the atmospheric pressure.

0 dBSPL?

dB SPL doesn’t mean there’s no sound pressure. Since sound is transmitted in the form of vibrations or waves, 0 dB SPL indicates that the pressure level of such sound waves is equivalent to atmospheric pressure. In reality, in most environments, 0 dB SPL represents a very quiet condition and might not be perceivable by the human auditory system.
dBSPL is mainly used to measure ambient noise levels, and it’s utilized across various sound-related fields, including environmental noise, output of acoustic devices, music, and more.

n underwater settings, the reference sound Pref is set to 1µPa instead of 20µPa. This relates to the sound propagation characteristics in water.
Water, being a different medium from air, exhibits distinct characteristics when sound propagates through it. Due to its denser nature compared to air, sound pressure variations are more pronounced in water, resulting in much higher values than in air.

For precise sound level measurements, weighting filters like dB(A) and dB(C) are often applied. These filters take into account human auditory characteristics to weight the sound level since human hearing is nonlinear, necessitating such weightings