Thursday, June 19, 2008

Traffic noise #2 - Grogans Mill North side


Measurements were taken on June 18th using the same methods as the first in Indian Springs. This measurement is intended to see what noise is generated from The Woodlands Parkway and what surrounding noise it may create in the area of a flyover. This is a rather complex site, not typical of The Woodlands. The flyover is the one going over Grogan's Mill Rd.

North Side On Grogan's Mill Rd near the East side apartments, the traffic is fairly tame moving in a 35MPH zone, and consisting of mostly sedans emitting an average of 75db as they pass the measuring meter. In the background, one hears a low drone of less than 70db from the parkway. There is an occasional sports car or truck which will momentarily raise the level as high as 90db, but most trucks emit noise less than 85db. Even a rattling pickup truck which I expected to be notable was measured at only 78db.

On the ramp onto Woodland's Parkway, as traffic accelerates away from Grogan's Mill towards the west, the sound level is not surprisingly higher. Surrounding traffic brings the meter to 75 db regularly but not continuously. The average observed level, mostly consisting of sedans, was about 78db. Some 6% of the traffic exceeded 80db; approximately 1% exceeded 85db. There is significantly more truck traffic coming under the parkway than from the north, and turning on to the ramp; this causes higher levels of noise at this location. I observed about a 3db increase in the average level of sedans and trucks at this location in short 10-15 second spurts as the traffic light at Grogan's Mill opened two lanes of traffic to turn on to the ramp. Typical measurements were: Concrete truck- 80, tow truck - 82, SUV with loud pipes - 87 db, sedan with loud pipes - 85 db, pickup truck with loud pipes - 90+ db. Pickup truck with loud bass audio speaker - 90db. A nearby HEB 18-wheeler transport truck registered 80 db even though it was far away and not directly passing by. A typical traffic burst would have about 12 seconds duration emitting noise at a 82-83 db volume, usually produced by two concurrently occupied lanes of traffic.

Then next measuring location was on the parkway itself on the northern side, as the traffic began to descend down the flyover. There were of course more trucks on the freeway than Grogan's Mill. The 45+ MPH speed of the traffic certainly cranked up the volume. A typical sedan emitted a 81 db level of noise. Traffic moved in bursts, controlled by the traffic light at Six Pines. Each here also burst and would last for varying times, from 20 seconds to 45 seconds. Each burst would typically range from 83-88 db 10-12 feet from the source. Here one could discern differences in tires, much more so than at lower speeds. A higher frequency pitch would be emitted by some tires. Some pickup trucks or vans with loud mufflers would ratchet up the volume into the 90's. There were several trucks that exceeded 90db and one dirt dumpster was measured at 99db. I asked myself where all of this noise was going, because below the flyover, I could hear very little of it. I concluded that the sound waves probably go up more than down because the road itself reflects the sound, and a lot of the irritating noise comes from mufflers, not the road.

South Side Measurements
I will be measuring the other side of this flyover in a few days and simply adding it here.

No comments: