Planned Maintenance

Alert: Due to planned maintenance, the HUD Exchange will be unavailable starting at 8:00 PM EDT today (4/25). The site will be available again on 4/26 by no later than 8:00 AM EDT.

Day/Night Noise Level Electronic Assessment Tool

The Environmental Planning Division has developed the Day/Night Noise Level Calculator, an electronic assessment tool that calculates the Day/Night Noise Level (DNL) from roadway and railway traffic. This is a web-based application of the existing Noise Assessment Guidelines (NAG). Derivations of the basic noise equation from the noise regulation, 24 CFR Part 51 Subpart B, were applied to a new application of the NAG.

Noise from aircraft and loud impulse sounds are addressed through this tool as well. Aircraft noise data, available from the neighboring airports, may be input for inclusion in the total site exposure. Loud impulse sounds are similarly accommodated once their presence has been confirmed.

Site Acceptability Standards:

  1. Exterior noise levels: Proposed HUD-assisted projects with a day-night average sound level of below 65 decibels are acceptable (see Standards in 24 CFR Part 51.103)
  2. Interior noise levels: Proposed HUD-assisted projects with a day-night average sound level of below 45 decibels are acceptable

Additional guidance on how to calculate the DNL for a proposed HUD-assisted project is available in the Department's guidebook The Noise Guidebook and the regulation 24 CFR Part 51 Subpart B, Noise Abatement and Control.

Access the Day/Night Noise Level Calculator

Feedback and Corrections

After using the DNL Calculator following the directions in the User's Guide, users are encouraged to provide feedback on how the calculator may be improved.

Please send comments or other input using Ask a Question. Enter "Environmental Review" in the "My question is related to" field.


Tools and Guidance

Day/Night Noise Level Assessment Tool User Guide

Day/Night Noise Level Assessment Tool Flowcharts


Related Information

Environmental Review Federal Related Laws and Authorities

Sound Transmission Classification Assessment Tool (STraCAT)

Noise Abatement and Control


System Requirements

Internet Explorer 10.0 or above

Adobe Reader