Polcak is a civil engineer by training and acoustical/noise control engineer by practice. He deals with transportation noise analysis and mitigation. Polcak's experience centers on the acoustical design of noise barriers, computer prediction and modeling of propagation, field testing and research, and impact assessment.
What are common workplace scenarios and challenges that you frequently encounter as an acoustical/noise control engineer? Can you take us through an example?
Much of my work is quality assurance/quality control in nature, in that I review technical analyses and provide guidance on interpretation of policy and application of criteria. Some of the biggest challenges center on reconciling evolving practices and state-specific policies with past studies, to ensure consistency and continuity over time.
The best example is the recent Federal Highway Administration (FHWA) noise regulation revisions, which became effective in mid-July 2011. Our last 12-month period has focused on developing and revising existing policy to conform to the revised regulation. All the while, there are ongoing studies and analyses, which must be considered in light of the new regulations and grandfathering considerations, all coordinated with FHWA.
What kinds of regulations is the Federal Highway Administration calling for, and how does that affect what you’re building?
There have been different details that have changed over the years, but this most recent revision to the regulation was issued last July. It sets out the general guidelines for criteria, that each of the states then establish for themselves. You have to have your own official written policy that governs the issue of highway noise in your particular state. It’s called the Procedures for the Abatement of Highway Traffic Noise and Construction.
What kinds of noise barrier developments are we talking about here? What are the end results of what you’re building?
There are two elements to the regulation. One is more of a mandate; it’s centered on the National Environmental Protection Act (NEPA) and all the requirements of doing assessments of environmental impacts. Whenever there is a federally funded project, you need to determine your existing noise levels, your future levels, and then determine if you have impacts. If you do have impacts, you have to consider mitigation of some form. Generally, the abatement of choice is the noise barrier, which is basically just a big vertical wall in between your highway and the adjacent sensitive area.
In general, whenever we identify that there’s a community or some other sensitive areas like churches, schools, or parks, we look to build these noise barriers. We have about 105 miles worth of barrier in the state of Maryland that have been built so far.
What other factors go into the acoustical design of noise barriers?
Factors that must be considered include current and future levels, which will dictate required effectiveness (noise reduction), site topography, actual land uses and types of receptors. Design parameters are primarily the height (how much the line-of-sight is broken), length (the "angular coverage" provided), and location between the source (highway) and receiver.
What kinds of impact assessment do you do? How does that work?
Impact assessment considers two factors: actual level, relative to the FHWA impact thresholds, and increase in noise level over existing levels resulting from a proposed project.
What are you able to do with the data you collect on transportation noise analysis?
Acoustic data collection serves two purposes; one as baseline information for impact assessment, and responding to citizen inquiries or complaints, and two as a method to validate the computer models.
What technologies and tools do you most frequently use?
For measurement, sound level meters are used to obtain existing noise levels. Computer prediction programs like FHWA's Traffic Noise Model (TNM) provide forecasts of future levels and include design tools for developing noise barrier designs.
How do you ensure that you have accurate data input and accurate computer models?
If we have a candidate area that we’re looking to assess, either just for noise impact or an actual noise barrier design study, the first aspect is to go out and physically measure the noise level at various locations, and at the same time, document environmental conditions that exist simultaneously with your measurement. You have to do classified counts of the traffic that’s going by as you do your measurements, documenting its speed, and hopefully you have reasonably neutral environmental conditions — no wind or rain. Once you take that real-world existing data, then when you go back and construct a computer model for that particular area, you, in a perfect world, can take that traffic, the associated speeds, all the trucks and other types of vehicles that you encountered in the field, plug that into your model, and ideally you will get the same noise level back from the model that you measured in the field. That’s a measure of your validation of your model.
That’s probably the biggest challenge of that whole process and procedure: getting things validated, getting reliable results out of your model. You physically develop the model, looking at terrain conditions, ground cover, and whether you have intervening buildings, or if you have existing barriers of any sort in the environment.
Any other challenges?
Obtaining accurate and complete data inputs for the computer models. TNM utilizes traffic parameters such as vehicle volumes, truck mixes, and speeds to arrive at noise level predictions. As with any computer model, the results are only as reliable as the input — recognizing, of course, the skill of the "modeler" in effectively and accurately constructing the model.
What kinds of work do you do with technical committees of the Transportation Research Board?
The TRB Technical committees are organized by specific topics areas — in my case, transportation-related noise & vibration — and provide a clearinghouse for research results, technical advances in the state-of-practice. They foster and identify research needs to advance the state of the art/practice. They also provide a forum for information exchange among "practitioners," such as technical specialists like me from different states and other transportation agencies. The Committees sponsor and organize conferences and workshops throughout the year to foster this "technology transfer" function.
There are a lot of ongoing projects (eight or ten of various types) that I’m involved with in some area: monitoring the technical exchanges from consultants that are in the midst of doing an analysis or may have some modeling issues. We do a fair amount of review of completed technical analysis. We also guide and coordinate a lot with our environmental planning folks that actually do the environmental documents. I very often get a phone call or two, either from another state or a consultant that’s doing research for some project somewhere, and very often I’ll even get phone calls from citizens that have questions about noise or the policy that govern noise and noise barriers.
What is the most satisfying part of the job?
Fortunately, in my overall function here with the State Highway Administration, I’ve been able to maintain a connection on a technical level. A lot of folks wind up having to evolve beyond that, or out of that technical arena when they get team leader status. In maintaining that “technical connection,” I feel I’ve been able to be contribute most effectively to the organization’s mission and goals using the expertise and experience I’ve gained over the years. That’s a rare opportunity, and I feel very fortunate and satisfied to have been able to give my best to the job.