Outdoor Noise Intrusion into Condos, Apartments, Hotels, Dormitories and Single-Family Homes  

by Nathan Sevener

Assessing and improving the sound insulation provided by residential building envelopes is one of the aspects of acoustics that we are most commonly asked to address for condos, apartments, hotels, dormitories, and single-family homes.  Residences may be located next to busy roads, near train tracks, under flight paths, or in just generally loud urban settings with accelerating buses, emergency vehicle sirens, honking horns, and other myriad sounds of the city. 

We begin our analysis by measuring the sound level at the project site.  For residential developments, we typically log the noise levels for 24 to 48 hours

and then determine the day-night average sound level, abbreviated L_dn or DNL; the average sound level during each hour of the day, abbreviated L_eq(hr); the sound level exceeded only 10% of the time, abbreviated L₁₀; and the sound level exceeded only 1% of the time, abbreviated L₁. 

Next, we create a 3-D computer model to predict the sound level over the facades of the new building, and we calibrate the model using the sound level data collected at the project site.  The model accounts for shielding, reflections off of nearby buildings, attenuation due to distance, and other factors.  The images below show modeling results from a couple of our recent projects. 

For smaller buildings, computer modelling of the sound distribution over the facades is not necessarily beneficial – sound level measurements at the site along with spreadsheet calculations can be sufficient For larger buildings, especially those where some facades will be exposed to much higher noise levels than others, computer modeling allows us to more accurately determine which portions of a façade should be designed to provide better sound isolation - avoiding costly over-design while still achieving project noise isolation goals.