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Q. How does my area qualify for a soundwall?   A. The two key factors under the Community Noise Abatement Program are:
  1. The residential area existed prior to the freeway opening date or major reconstruction completion.
  2. Outside noise levels exceed 67 decibels (Leg)
Q. Why is the 67 decibels (Leg) level so important? A. This is the noise level established by Federal and State agencies, which must be exceeded before impacted neighborhoods are eligible for mitigation.
Q. What does Leg mean? A. It is the steady noise level equivalent to fluctuating traffic noise over a given period of time.
Q. When are noise levels usually measured? A. In the greater Los Angeles Area our studies have shown that the highest noise measurements usually occur between 9:00 a.m. and 3:00 p.m. and not at peak congestion times.
Q. Why aren't noise measurements taken during the peak congestion time? A. Traffic noise is speed related. i.e., as vehicles move faster; they produce more noise. Likewise, when traffic is stop-n-go or at low speeds, noise levels are also lower.
Q . Why does it seem noisier late at night and early morning? A. Due to the fact that the surrounding area is quieter at these times, the masking effect of other noise does not screen the freeway noise. This usually makes the freeway noise more prominent but lower than the midday level.
Q. Why are noise measurements taken for only ten minutes? A. Our measurements on heavily traveled roads have shown that a ten-minute period is sufficient to reliably reflect an hourly noise level.
Q. Why is there a soudwall on the other side of the freeway or just down the road and not in my area? A. There are many factors which affect noise levels even when traffic volumes are the same. These differences usually happen when the terrain changes the freeway curves in a different direction the freeway elevation changes from above to below ground level. Also developers of the adjacent property have sometimes constructed soundwalls.
Q. Why can't you place a soundwall to protect our area from cars running off the freeway? A. Soundwalls are not intended to act as safety barriers. There are other reliable methods used such as installing guardrails to protect against vehicles running off the road. All improvements, whether to reduce noise or enhance safety, have to meet specific criteria and be justifiable on their own merits. Cost is always a factor.
Q. Why are soundwalls built to protect commercial property in some locations? A. Commercial property in itself is not eligible for soundwall protection. However, when designing a wall in a particular location safety, aesthetics or continuity will sometimes dictate gap closures, which can end up protecting non-eligible property. Also in some instances, the walls were privately funded.
Q. Are soundwalls required by Federal, Caltrans, and/or City offices? A. As part of the general environmental review process associated with all projects, Caltrans is required to evaluate traffic noise impacts. Impacted areas are considered for noise mitigation, by implementing noise abatement when reasonable and feasible.
Q. What is "decibel energy" and how is it accurately measured? A. Decibel Energy is the relative intensity of sound defined on a logarithmic scale. The unit of measurement for sound intensity is the decibel (dBA) as measured on the "A" scale of a standard Sound Level Meter. The "A" scale most nearly approximates the response of the human ear to sound. While an increase of 2 or 3 dBA may be hardly noticeable, and increase of 10 dBA doubles the apparent noise level.
Q. When will my soundwall be built? A. If your soundwall is on the May 1989 List, the list shows the tentative schedule for construction. MTA is currently working  on the schedule for the Post May 1989 List. (See MTA policy for details)
Q. Is my soundwall funded? A. The May 1989 List was funded in August, 1999.  MTA is currently working on the funding strategy for the Post May 1989 List (See MTA policy for details)
Q. Who should I contact if my soundwall is not on either list? A. Contact the Environmental Group (Noise Study) at Caltrans Jin Lee, P.E., Senior Transportation Engineer, Phone number: (213) 897-3312, Email Address:Jin_S_Lee@dot.ca.gov
Q. How do I look up the Post Mile for my area? A. An approximate post mile can be estimated from the Post Mile Map.  Look between project limits found in the list (May 1989 & Post 1989 List) to determine whether your soundwall is located in that area.
Q. What is the Senate Bill 45? A. Senate Bill 45
Q. If my soundwall is on the Post May 1989 List, who do I contact at MTA about funding and scheduling for my soundwall? A. Marta Maestas, Project Manager, Phone number: (213) 922-3054, Email Address: MaestasM@MTA.NET
Q. Why does it take so long to build my soundwall? Click Here for the Answer
Q. How is my soundwall prioritized? A. Your soundwall is assigned a PIN number based on a formula, which considers the existing noise level, the anticipated noise reduction, the number of residential units impacted and the project’s estimated cost.
Q. On the MTA Retrofit Soundwall Programl list, how can I move my soundwall up in higher priority? A.    MTA will receive a 1/3 contribution from the city.

b. An individual can meet with the local city to create a "Benefit Assessment District" for building a soundwall. When the soundwall comes up on the list the city will be reimbursed.

Q. Does a school automatically qualify for a soundwall? A. Typically in a residential area, the first criteria for a project to qualify for a soundwall is that the residence has had their homes built before the freeway. In contrast, a school does not have this initial qualifying criteria, instead, there are two approaches to the noise abatement criteria for schools. The first approach is when the interior noise abatement criteria level exceeds 52 dBA. This study is done when the windows and doors are closed and the air-conditions are off. If the noise level exceed 52dBA, the Department of Transportation shall provide noise abatement to reduce the noise level below the criteria. 

Page Last Modified 10/13/10 09:38
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