With construction on the new Circuit of the Americas track underway in Southeast Austin after a quick approval process, some are uncertain about what benefits and detriments the track will have for the city in the long run. Unable to find evidence of any kind of environmental or noise study, I decided to build a computer noise model of the track and the surrounding areas using SoundPLAN to investigate the potential noise exposure of the surrounding area caused by vehicles operating on the track.
These are the data and assumptions that went into the model:
- Terrain data and image data for the area came from the National Map. Construction of the track will result in elevation changes in certain places, especially along the track itself, but I don’t have access to that data so I had to assume the elevations would be close to existing conditions. Long-distance propagation like this should not be highly affected by the types of elevation changes that the track area will undergo.
- Track layout and facility building locations were taken from the posted Conceptual Master Plan at the Circuit of the Americas website.
- The noise source was assumed to be a single open-wheel car circling the track alone. I was unable to locate noise data for a Formula 1 vehicle, but measurement data for an IndyCar pass-by was presented by Harris, Miller, Miller & Hanson in their analysis of the Baltimore Formula 1 track. Formula 1 and IndyCar vehicles are indeed different, but should be similar enough for the purposes of this study. If anything, this is a conservative substitution as Formula 1 vehicles operate at more extreme parameters.
- Facility Buildings that could provide some noise shielding, including the grandstands and maintenance buildings, were included in the model.
- Natural Seating Areas around the track were modeled as grassy berms to provide noise shielding where they are located.
The noise model predicted the maximum level experienced based on a single trip around the track for one car. Multiple cars in a group would, of course, be additive and would increase the predicted levels based on the number of cars according to logarithmic addition. 2 cars would be ~3 dB louder than one car, 3 cars would be ~5 dB louder than 1 car, 4 cars would be ~ 6 dB louder than one car, 5 cars would be ~7 dB louder than one car, and so on.
The results for the entire analysis area are shown below:
To the West, there appear to be no real problems. Out in the country the car on the track would be clearly audible outdoors, but probably not disturbing. To the North, South, and East, the track is much closer to the property line and to residences. A single car would register levels as high as the upper 80′s dBA for the closest residences, which most people would find disturbing, both indoors and outdoors.
Scanning the satellite images, I located what appear most likely to be residential structures close to the track and included them as buildings in the model. They are shown as dark blue boxes in the figures.
On the north side of the track, the houses near the entrance can expect noise exposure from a single vehicle pass-by ranging from about 70 dBA to 80 dBA. This would be difficult to talk over in an outdoor environment, and would be clearly audible inside of most homes (though not necessarily disturbing). Multiple cars on the track would likely increase interior sound exposure to levels that most people would find annoying.
To the East, the track is closer to residential buildings, so greater impacts are expected. Noise exposure between the mid 70′s and mid 80′s dBA from a single car pass is predicted for homes in this area. Assuming a difference of about 20 dBA outside to inside (typical for residential buildings), inside noise levels could be expected between 55 and 65 dBA for a single car. These levels correlate to loud but normal conversation volumes, meaning that people inside these houses would need to either speak loudly or wait for a car to pass to carry on a conversation.
Predicted noise exposure on the south side is greater still, with some buildings expected to be exposed to levels in the mid to upper 80′s dBA for a single vehicle pass. With these exterior noise levels, it may be difficult to carry on a conversation inside of any building with ordinary construction.
There are still other potential noise impacts to consider beyond just the sound from a single car on the track affecting residences in the area.
- Other noise sources, such as traffic and the cheering of spectators may produce noise sufficient to disturb residents of the area.
- Race car noise may stress or frighten livestock.
- Noise signatures from other types of cars using the track, such as the V8 Supercars, may have lower frequency content, resulting in noise with longer carry and better ability to penetrate building structures.
- It appears very likely that the track will be operating in exceedance of the Austin noise ordinance.