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 DO YOU HEAR WHAT I HEAR?
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As I’m typing this at 11:45 PM sitting in my home in a residential subdivision in Bossier Parish, Louisiana, I hear a B-52 bomber low overhead preparing to land at Barksdale. I hear a slight knock of the ceiling fan on every other revolution from an off-balanced blade. I hear a train horn and passage of the freight cars. I hear someone out on the state highway demonstrating the acceleration of their 35-year-old IROC Z.
So, your typical North Louisiana weeknight.
Am I hearing the sound of American freedom, or an obnoxious, ear-splitting roar that I’m waiting patiently to end? Do I hear essential goods being shipped across country, or an annoying, brain-piercing airhorn at irregular, disruptive intervals? Do I hear a soothing night melody in my bedroom to help me drift off to sleep, or the last gasp of a discontinued, clearance isle, builder-grade fixture? Is that the sound of your teenage years roaring back for a fond recollection, or a Joe Dirt wannabe showing off how much louder his ride is with the open headers.
Are all those I listed just sounds, or noises? Sound is generically defined as vibrations that travel through air or another medium that can be heard when they reach a person’s ear. Noise is sometimes used as a synonym for sound; however, “Noise” is a generally referred to as sound that is unwanted, inappropriate, or harmful.
In reading and researching for this topic, I found a very apt definition of “Noise” from Ambrose Bierce’s The Devil’s Dictionary – A stench in the ear. Unwanted and harmful sounds fit that definition perfectly.
Oil and Gas operations have been commonplace in many regions of the country for longer than some of the readers of this submission have been alive. There is no doubt the scale and intensity of these operations have increased in the last 10 years as both demand for petroleum products and technology to unlock previously inaccessible reserves has grown. Combined with population growth and residential development of previously rural sectors of the community, the proximity of oil and gas operations to greater concentrations of the public at large is becoming commonplace. As people have moved closer to well sites, and well sites have moved closer to people, the inevitable conflict of sharing the same spaces has put pressure on oil and gas operators and municipalities to cooperate in a restructure of how to balance efficient resource development with the least possible disruption to the communities.
Before we dive into any specific oil and gas noise ordinances, we need to get some terms defined and understand what is being measured.
Sound Measurement Basics
Sound vibrations have 2 characteristics we will look at for the scope of this discussion: Frequency and Amplitude. The frequency, or number of vibrations in one second, are measured in Hertz (Hz). This corresponds to a low or high pitch that is heard. A typical healthy human ear can detect frequencies between 20 and 20,000 Hz. There are some interesting frequency test tones on the internet that have qualifiers like.. “if you are over 18 years old, you can’t hear this tone…If you are over 40 you can’t hear this tone”...etc. Good stuff to fill that void between not starting any work right before your lunch hour.
The decibel (dB) is the standard measurement of a sound’s amplitude, or the size of the vibration. Also called the intensity. It denotes the ratio between two quantities which are proportional to power, the number of decibels corresponding to the ratio of two amounts. That last sentence is a bit much, but basically means ratio of power in to power out regarding the amplitude measure. I insert that because many state and local noise ordinances define the decibel in this way.
The bel is the base amplitude measurement, and a decibel is 1/10 of a bel. The decibel is used as the standard measurement value because a one-decibel difference in loudness between two sounds is the smallest difference detectable by human hearing.
 Frequency and Amplitude are objective quantities that can be measured; however, the perceived loudness of a certain decibel value sound can be affected by the frequency. For Example, a sound with a frequency of 100Hz at 60 dB will not be perceived to be as loud as a 1,000 Hz sound at 60 dB. So, the frequency of a sound can be just as important of determining if a sound is considered a Stench to the ear as the amplitude. For this reason, different Weighted Networks are used for adjusting sound readings to represent what the human ear is hearing. The three most used decibel weighting networks are ‘A’, ‘C’ and ‘Z’.
Z-weighting is a flat frequency response across the 8 to 20,000 Hz spectrum with no weighting of frequencies for human ear sensitivity. The ‘Z’ represents Zero weighting. It’s used for environmental noise readings and octave band analysis. Measures the actual sound. Sometimes referred to as dB (Flat) or dB(Z)
A-weighting is used to make decibel readings conform to the typical frequency sensitivity range of the human ear, 500 to 6,000 HZ. A-weighting tends to minimize or cut out the frequencies below and above that range. If a reading is weighted using this network, it will be denoted as dBA.
C-Weighting is used for weighting peak sound measurements (short term and sudden bangs, crashes, booms) and for lower frequency 500 Hz and less. These lower frequency sounds are often “felt” rather than “heard” and travel farther distances and not easily defeated by physical barriers.
The Decibel Scale
Near (but not absolute) silence is considered 0 dB. This is also called the Threshold of Hearing (TOH). The range of intensities that the human ear can detect is so large, the decibel scale used to measure intensity is a scale based on powers of 10. This type of scale is sometimes referred to as a logarithmic scale. A sound that is 10 times more intense than the TOH is 10 dB. A sound that is (10*10) or 10^2 or 100 times more intense is 20 db. A sound that is (10*10*10) or 1,000 times more intense is 30 db. A sound that is 10*10*10*10, or (10^4), or 10,000 times more intense is 40 db. And so on. This scale is based on powers of 10. If one sound is 10x times more intense than another sound, then it has a sound level that is 10*x more decibels than the less intense sound.
As a result of the decibel logarithmic scale, sounds of same or varying levels cannot simply be added and subtracted arithmetically. There is some funky math that takes place to get there, but as a rule of thumb if a sound source doubles, the resulting new decibel level increase by 3 dB.
The figure below shows how to add multiple sources with varying dB measurements. If you are dealing with 3 or more, make them into pairs, apply the readings according to the nomograph below.
If I had one frac pump at 60 dB, and a second pump at 64 dB, the combined dB reading would be approximately 65.1 dB
There are hundreds of decibel equivalent charts out in the Web, go find your favorite. Here is just one I grabbed to help bring this decibel stuff to some familiar sounds.
Operational Noise Abatement
As a result of increased pressure to reduce noise impact of operations in increasingly populated areas, operators have spent great effort and expense to erect barriers, adjust schedules, relocate pad sites and communicating in advance the expected impact of their operations on residents. Notification of what to expect and for how long can be very effective in easing the impact of drilling and completion operations.
In regard to engineering controls to reduce noise from operations, operators are erecting specifically designed sound blocking and absorption panels to mitigate noises that can’t be eliminated by process scheduling and equipment substitution.
Below are pictures of site-specific sound abatement barriers and equipment. The fixed wall temporary and portable barriers are shown. These barriers are designed to block or absorb a range of sound frequencies from 20 Hz to 4,000 Hz. The decibel reduction is greater on the higher frequency range due to the nature of the higher frequencies to be short range and easiest to block and reflect.
Regulatory Framework for Noise Control
At the Federal level, regulations were put into effect through the Noise Control Act of 1972 and Clean Air Act Title IV in the late 60s and early 70s to regulate non-workplace noise, but by 1981, these regulations and sub-agencies responsible for enforcing these regulations were effectively shut down. This shifted the primary responsibility to states and local governments for addressing non-occupational noise issues.
With the Federal oversight burden removed, many states and local governments enacted specific and appropriate community noise standards for commercial and residential noise control. And in the past 20 years, states and local governments have put into place or attempted to put into place noise regulations specific to oil and gas operations.
This In 2009, the State of Louisiana, Office of Conservation issued Order # U-HS, that provided a regulatory framework for the Exploration and production of Gas from the Haynesville Zone in Urban areas. U-HS defined basic noise standards to be met for state regulated oil and gas operations specific to the Haynesville Shale. More recently, the parishes most affected by oil and gas operations have begun to enforce existing noise ordinances and seek to develop more detailed, measurable and enforceable regulations with input from operators and Industry trade groups and looking outside the state to evaluate what is working elsewhere.
Two governing entities that are considered to have model noise regulations pertaining to oil and gas operations in urban areas from a regulatory standpoint are the City of Fort Worth and the Colorado Oil and Gas Conservation Commission. I’ll include links to those ordinances rather than try to summarize or repeat here. Most existing and in process ordinances will contain common elements:
- Defined terminology to eliminate vague or misleading statements
- References to recognized standards for measurement.
- Specific noise limits for defined time intervals
- Realistic noise limits based on relevant measurements of operation-specific equipment and orientation.
- Established ambient sound level baselines for the specific area of operations
- Account for changing environmental conditions
- Allowance for correction of non-compliance
- Appropriate enforcement measures for continued non-compliance
Regardless of media perception and presentation, oil and gas operators, private residents, and governmental bodies enjoy a great deal of cooperation and working to mutual benefit daily. These relationships will continue to thrive as the need for more production drives increased infrastructure, increased tax revenue to municipalities and strengthening of local economies.
Related oil and gas ordinance links:
https://codelibrary.amlegal.com/codes/ftworth/latest/ftworth_tx/0-0-0-17850
https://cogcc.state.co.us/reg.html#/overview
http://www.caddo.org/543/Oil-Gas
https://library.municode.com/la/bossier_city/codes/code_of_ordinances?nodeId=PTIICOOR_CH46EN
Please contact Steven Roberts for more information on noise abatement services from Brammer Engineering.
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