Sound Pressure Level Formula

Sound Pressure Level

Sound pressure is the pressure applied by the sound waves. The sound pressure level is the ratio of the actual sound pressure and the reference level which is the lowest intensity sound that can be heard by maximum people. In other words, a sound pressure level decides the amount of pressure on the sound.  It provides the logarithmic measures of rms value of the sound pressure to the reference value of the sound.

It is expressed in (dB).  

The sound pressure level formula is expressed by

L_p = 20 log₁₀(p_rms / p_ref)

Where,

P_rms = root mean square sound pressure in Pa,

p_ref= reference sound pressure in P_a. (20 μP_a)

Solved Example

Example 1: Determine the sound pressure level if the rms pressure value is given as 30 μP_a.

Solution:

Given

P_rms = 30 μP_a

p_ref = 20 μP_a

The sound pressure level formula is given by

L_p = 20 log₁₀ (p_rms / p_ref)

L_p = 20 log10 (30 / 20)

L_p = 3.52 dB

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