LAeqT

LAeq,T stands for the A-weighted equivalent continuous sound level over a specified period T. It is a measure of the steady sound level that would produce the same total sound energy as a fluctuating sound signal during the time interval T. LAeq,T is widely used in environmental noise assessments and occupational noise monitoring to summarize long-term exposure with a single representative value.

Mathematically, LAeq,T is defined as the A-weighted level that satisfies

L_Aeq,T = 10 log10 (1/T ∫_0^T 10^{L_A(t)/10} dt),

where L_A(t) is the instantaneous A-weighted sound level in decibels. In practical measurements, this integral is approximated by summing weighted samples: LAeq,T = 10 log10 (1/T ∑ Δt_i · 10^{L_A,i/10}), with Δt_i representing the sampling interval and L_A,i the A-weighted level at each sample.

LAeq,T is used with various time windows, such as 24-hour periods or subdivided day, evening, and night windows, depending on regulatory or assessment needs. It emphasizes the energy content of the sound signal over the period rather than peak or instantaneous values, making it more representative of cumulative exposure.

Measurement and interpretation methods: LAeq,T is obtained with sound level meters set to A-weighting and capable of integrating over the chosen period. The resulting value serves as a basis for compliance with noise limits, impact assessments, and health-related guidelines. It is a type of Leq (equivalent continuous level) and is distinct from maximum or peak values such as L_Amax.

See also: Leq, L_Amax, A-weighting.