L_eq - Equivalent Sound Level

Equivalent Sound Level - L_eq - quantifies the noise environment as a single value of sound level for any desired duration

The Environmental Protection Agency - EPA - has adopted a system of four "sound descriptors"

• A-weighted sound level
• Sound Exposure Level - L_s
• Equivalent Sound Level - L_eq
• Day-Night Sound Level - L_dn

to summarize how sound is heard and measured, and to determine the impact of noise on health and welfare.

Equivalent Sound Level - L_eq

quantifies the noise environment as a single value of sound level for any desired duration. This descriptor correlates well with the effects of noise on people. L_eq is also sometimes known as Average Sound Level - L_AT.

Equivalent Sound Level - L_eq - can be expressed as

L_eq = 10 log [(1/T) ∫ p_A² dt/p_ref²]         (1)

where

L_eq = equivalent sound level (db)

T = time period (s)

p_A =  sound pressure (Pa, N/m²)

p_ref = reference sound pressure ( 20 10^-6  Pa, N/m²)

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