Q: How is the 10 dB nighttime penalty applied?

A: It is added to the nighttime Leq inside the log term before time-averaging, effectively doubling the perceived impact of quiet night hours.

Q: Can Ldn drop below daytime Leq?

A: Yes, because the 24-hour pooling dilutes peak day values when night readings are low.

Q: Is this for official compliance reports?

A: No, it serves as a preliminary estimation only and cannot replace a qualified/licensed engineer review.

Q: How does Ldn differ from Lden?

A: Ldn has two periods: day (7am–10pm) with no penalty and night (10pm–7am) with a 10 dB penalty. Lden splits the day into day and evening and adds 5 dB to the evening (19:00–23:00) as well as 10 dB to the night (23:00–07:00).

Ldn Calculator

Compute 24-hour Ldn instantly from day & night Leq values.

Daytime Leq (7am–10pm) dB

Nighttime Leq (10pm–7am) dB

Day-Night Average Sound Level (Ldn)

0.0 dB

Formula: Ldn = 10 * log10((15/24)*10^(Ld/10) + (9/24)*10^((Ln+10)/10))

Note: This tool computes the 24-hour Ldn metric by applying a strict 10 dB penalty to nighttime noise (22:00 to 07:00) using 10*log10 time-averaging. For preliminary estimation only, not a substitute for review by a qualified/licensed engineer.

Understanding the Day-Night Average Sound Level (Ldn)

Urban planners and environmental consultants often require a consistent metric to assess environmental noise over a 24-hour period. The Day-Night Average Sound Level (Ldn) serves this purpose by providing a single figure that accounts for the varying sensitivity to noise during different times of the day. This calculator offers a fast, standards-aligned way to compute the Ldn figure from measured daytime and nighttime equivalent sound levels (Leq) readings, bypassing manual spreadsheets and complex calculations. It specifically applies a strict 10 dB penalty to nighttime noise (22:00 to 07:00), recognizing the increased annoyance caused by sound during these hours, using the standard 10*log10 time-averaging method.

This tool simplifies the process for preliminary assessments, making it easier to gauge the potential impact of noise in a given area. The formula used accounts for the different durations of day (15 hours) and night (9 hours), and precisely implements the unique 10 dB nighttime weighting factor essential for Ldn calculations.

How to Use This Ldn Calculator

Enter your measured daytime equivalent sound level (Leq) in decibels into the "Daytime Leq" field.
Enter your measured nighttime equivalent sound level (Leq) in decibels into the "Nighttime Leq" field.
The computed Ldn value will update instantly below in decibels (dB).
Review the displayed 10*log₁₀ formula to confirm the 10 dB nighttime penalty was applied in the calculation.

FAQ

Q: How is the 10 dB nighttime penalty applied?: A: It is added to the nighttime Leq inside the log term before time-averaging, effectively doubling the perceived impact of quiet night hours.
Q: Can Ldn drop below daytime Leq?: A: Yes, because the 24-hour pooling dilutes peak day values when night readings are low.
Q: Is this for official compliance reports?: A: No, it serves as a preliminary estimation only and cannot replace a qualified/licensed engineer review.
Q: How does Ldn differ from Lden?: A: Ldn has two periods: day (7am–10pm) with no penalty and night (10pm–7am) with a 10 dB penalty. Lden splits the day into day and evening and adds 5 dB to the evening (19:00–23:00) as well as 10 dB to the night (23:00–07:00).