Tuesday, June 17, 2008

Traffic Noise in The Woodlands Texas - Indian Springs


I have been concerned about the growing road noise level in Indian Springs for several years. This article documents my first findings after recently measuring the noise but does not provide any commentary on the results. I am holding that pending more investigations, additional thought and others' opinions. There has not been much data that I could find to indicate whether the noise here is normal or abnormal, except in the Handbook of Road Technology reference below. I decided to take a pragmatic view of the issue and measure the noise level we experience here at peak traffic times - at rush hour in the morning and in the evening to compare with observations elsewhere.
Background
Traffic noise consists of a varied number of components which affect our comfort level in different ways. Variables which affect the volume and frequencies of the noise include road surface, tire material and style, fuel of the automobile, muffler, transmission gear ratios, weight of the automobile, stereos and speakers, velocity of the automobile and the performance of the driver. Higher frequency noise is rapidly reduced by vegetation and distance, whereas low frequencies are not so easily attenuated, travel further distances and tend to bother residents more.

Typical sound volume benchmarks are easily related to traffic noise volume.
Facts:

  • Each 10 db increment doubles the volume, therefore 100 db is 16 times 60db
  • If it sounds loud, it measures loud
  • If you hear it in the house, it is dominated by low frequencies
  • Public annoyance legal threshold is 85db
  • Sustained exposure may result in hearing loss at or over 95db
  • Short term health danger begins at 105db
  • Maximum measurable noise level is 194db
  • Piano Fortissimo is 84 to 103db
  • Acceptable perceived levels are dependent on time of day or the individual's daily routine - some people work at night
  • Acceptable perceived levels are dependent on type of neighborhood and expectations in the living style of that neighborhood
  • OSHA declared a time criteria for exposure to various sound volumes
    • Maximum daily 8 hours at 90db
    • Maximum 1.0 hour at 105 db
  • If it hurts, it is usually over the legal limit in any public place
  • If house visitors ask about it, it is generally too loud
Measured benchmark reference data
  • TV at normal listening volume = 56db
  • TV at full volume = 78 db
  • Birds singing = 63 db
  • TVfull = 5 times volume of Tvnormal
  • Birds singing = 1.6 times Tvnormal
Method of measurement
  • Near source measurements 8+ feet away
  • Radio Shack Sound Level Meter mounted on tripod
  • No frequency measurements were taken
  • Visually measured instant peak volume only
  • 35 MPH speed zone
  • Three and four lane road at three nearby locations
  • Measured on concrete and asphalt surfaces
  • Equipment sensitive to wind velocity n- did not measure in high wind
  • Measurements taken at peak morning and afternoon traffic situations
Observations
  • Observations relative to the benchmarks and information above:
  • Typical sedan = TV at full volume
  • Loaded concrete truck = 1.8x sedan
  • Diesel pickup = 3x sedan
  • Pickup with loud mufflers = 5x sedan
  • 18-wheeler = 5x to 16x sedan
  • Most motorcycles = less than sedan
  • Motorcycle with loud pipes = 12x sedan
Observations in db
  • Concrete truck - 88db
  • Loud sedan - 90db
  • Most sedans - 77db
  • Heavy duty truck - 81db
  • Accelerating Sports car - 86db
  • Motorcycle with loud pipes - 90db
  • 18 wheeler moving van - 92db
  • Diesel pickup truck with loud pipes - 94db
  • Van with loud pipes - 92 db
  • Loudest vehicle observed - 97db
My estimate is that about 3% of the automobiles passing by at this location were registering above 85db at my measuring station.
References:
  1. Galen Carol Audio
  2. Handbook of Road Technology

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