RHOWS

RHOWS - Reliable high-order wave simulations

City noise


Noise pollution is one of today’s most serious environmental health hazards. Traffic noise alone is linked to cardiovascular disease, sleep disturbance, impaired learning in children, and reduced quality of life.


To build healthier cities and protect quiet zones such as national parks, we need tools that can accurately predict how sound spreads from traffic, industry, wind farms, and other human activities.


A particular challenge is low-frequency noise (below 200 Hz). Unlike high-frequency sound, it travels far, penetrates buildings, and is difficult to shield against. Major sources include road, rail, and air traffic, construction sites, wind turbines, and indoor systems such as HVAC and machinery.


In the animation below, SoundSim360 is used to simulate sound propagation from a 50 Hz ground-level source (such as a bus) outside the Ångström Laboratory in Uppsala, Sweden. The simulation captures both transmission and reflection of sound at the building facades, providing a realistic picture of how low-frequency noise spreads in an urban environment.

Unfortunately, existing commercial software relies on ray-tracing methods, which cannot capture four critical aspects of real-world acoustics:


  1. Low-frequency sound
  2. Complex geometries and terrains
  3. Sound transmission through walls and buildings
  4. Transient and broadband sources

 

SoundSim360 is a next-generation, high-fidelity sound simulation tool designed to overcome these limitations. Built on over 25 years of research in advanced numerical methods, it models the full physics of sound propagation in both outdoor and indoor environments. Unlike ray-based approaches, SoundSim360 accurately handles low-frequency noise, complex 3D terrains, reflections and transmissions through walls, and transient or broadband sources.


To illustrate the differences between SoundSim360 and ray-tracing approaches, the figures below show the predicted sound pressure levels at a height of 2 meters from a 31.5 Hz source in the area around the Ångström Laboratory. The first figure presents the results obtained with SoundSim360, while the second shows the corresponding results from Nord2000, as implemented in SoundPLAN 9.1. Nord2000 is a ray-tracing method that has recently been adopted as the standard computational model for road and railway noise in Sweden.

SoundSim360

A comparison figure also visualizes the difference in predicted noise levels between SoundSim360 and Nord2000. The sharp contours visible in the Nord2000 results are characteristic of ray-tracing methods, which struggle to model edge diffraction—a critical phenomenon for low-frequency sound. As a result, noise levels in the shadow zones behind buildings are often underestimated, sometimes by as much as 30 dB. In contrast, the wave-based approach used by SoundSim360 captures diffraction effects naturally, providing a far more realistic representation of low-frequency propagation.

Nord2000

SoundSim360 and Nord2000 difference

From urban planning and environmental protection to wind farm analysis and building acoustics, SoundSim360 provides the insights needed to design quieter, healthier spaces. Powered by GPU acceleration, it combines scientific accuracy with the computational performance required for simulations at the city and building scale.