Use this calculation for a first-order acoustics estimate when the stated geometry, propagation model, averaging convention, reference quantity, and SI units match the measurement or design problem.

First Decibels

A finite measured or assumed value, expressed in dB.

First Seconds

A finite measured or assumed value greater than or equal to 0, expressed in s.

Second Decibels

A finite measured or assumed value, expressed in dB.

Second Seconds

A finite measured or assumed value greater than or equal to 0, expressed in s.

The implemented rule is: Two-interval equivalent continuous sound level from each interval's level and duration.^[1]

Leq Decibels

The calculated leq decibels, expressed in dB.

This is an idealized calculation rather than a complete acoustic simulation or measurement. Reflections, boundary conditions, directivity, damping, frequency dependence, near-field behavior, background noise, transducer response, temperature, humidity, and geometry can change a real result.

Confirm important results with calibrated measurements or a model that includes the actual geometry, materials, boundaries, source directivity, and frequency-dependent losses. Preserve the reference quantity and weighting whenever a result is expressed in decibels.

• Day Night Level Dnl

  24-hour day-night level from representative 15-hour day and 9-hour night Leq, with a 10 dB night penalty.

• Noise Metric Sel From Event Leq

  Sound exposure level from event Leq and measured event duration relative to one second.

• Railway Pass By Sel

  Sound exposure level from a pass-by Leq and event duration relative to one second.