Northern Kentucky Airport Noise Study

Acoustic Studies Group

Northern Kentucky University

Highland Heights, Kentucky

http://physics.nku.edu/asg/noiseindex.html

Introduction

The dramatic growth of the Cincinnati/Northern Kentucky International Airport has introduced a number of environmental problems, not the least of which has been noise pollution and abatement.The increased number of arrivals and departures, along with the construction of new runways, has elevated the integral and differential noise levels in the vicinity of the airport.Attempts to alleviate the problem have included buyouts of impacted homes and businesses, modifications to improve the acoustic characteristics of similar structures as well as efforts to reduce the source levels.Both contractors and Federal Aviation Administration (FAA) personnel have monitored sound levels in and around the airport for many years.In spite of efforts to alleviate the sound levels associated with the airport, residents near the airport, and proposed expansion areas, continue to object to conditions.

In an effort to discover exactly what the airport is doing to alleviate this problem, this study was proposed and approved.So, what does the airport do to lessen the impact of airplane noise on the surrounding communities?This responsibility falls upon the shoulders of the FAR Part 150.

FAR Part 150

Whenever an airport plans an expansion or a change in operations, it is required to perform a study examining how the proposed change will impact noise in the surrounding communities.The Federal Aviation Regulation that specifies the “procedures, standards, and terminology” that are required in this study is the FAR Part 150 (http://physics.nku.edu/asg/far150.htm).Before the change is to occur, the FAA must approve the study and give permission for the changes to be implemented.The Cincinnati/Northern Kentucky International Airport has just recently performed one of these studies (http://www.landrum-brown.com/ActiveEnvProjectsCvg/).

The Acoustic Study Group is researching exactly what goes into the FAR Part 150.We have discovered some issues that may affect the accuracy of the results of the study.These issues will be discussed later.For a summary of what is needed for a Noise Compatibility Program to be accepted by the FAA, view http://physics.nku.edu/asg/noise150check1.htm and http://physics.nku.edu/asg/noise150check2.htm for Part I and II of the Noise Compatibility Checklist.

Compliance with all noise regulations is acutely related to preditions associated the Integrated Noise Model (INM)(http://www.aee.faa.gov/aee-100/inm/geninfo.htm).This model outputs a noise contour map using operational data from the airport.The noise contour map showsthe predicted daily noise exposure in the vicinity ofthe airport. The different variables and other requirements of the INM can be found at http://physics.nku.edu/asg/noiseinmcheck1.htm and http://physics.nku.edu/asg/noiseinmcheck2.htm.

What are we investigating?

As noted above, the ASG is examining the Noise Compatibility Program as well the INM, and how the map is created.Below are two possible problems with the INM and Part 150:

1.In the INM and Part 150, no gray area is observed, meaning there is a clear line dividing who is eligible for assistance for house insulation, or other forms of noise abatement.One household may be able to receive assistance, but their next-door neighbor may not.A gray area should be observed to where necessary measurements could be made at that particular location to see if assistance is appropriate.These households should be given notification that assistance is available and given substantial time to apply for assistance.Houses closer to the outer noise contour should get precedence over others.

2.In the INM, the noise contours are created without any consideration of weather.When there is cloud cover over the are surrounding the airport, the integral of decibel level should be affected, if not in intensity, then over time, especially since the INM takes into account that every day is a sunny day.Since the equations used for the INM use integral equations extensively, the effect could be extremely considerable.

Obtaining data that shows a difference between integral noise levels due to weather is one of the central purposes of the measurements taken.How we shall collect this data and how it will be processed will be discussed later in greater detail.

Recording Data

When collecting Data, there will be one person positioned along the side of a runway, and another positioned a considerable distance away (far enough that the airplane is at least a hundred feet in the air).The person near the airport is responsible for recording the following variables:

1.Time of takeoff/landing

2.Airplane registration number (located on the side of all aircraft)

3.Date of Measurement

4.Measurement Number for the particular date

5.Action (Takeoff/Landing)

The person at the actual data taking location is responsible for recording the following things:

1.Time that the airplane is directly overhead

2.The weather condition (supplied by the National Weather Service located at the airport), recorded the hour before, during, and after recordings are taken), (consists of weather description, temperature, humidity, wind speed, and air pressure), (must be noted if quick change in weather type occurs)

3.An Audio recording of the airplane using a Digital Audio Tape (DAT) Recorder

4.A Real time recording of the decibel level (A weighted), with a frequency of 10 Hz, using a decibel meter and laptop computer.

Processing Data

The data recorded then is put into a spreadsheet; the index for the spreadsheet is as follows:

A=AIRPLANE REGISTRATION NUMBER (used to tell the planes apart from each other)

B=DATE OF MEASUREMENT

C=MEASUREMENT NUMBER FOR THAT DAY (MAY NOT ALWAYS BE IN EXACT

ORDER BECAUSE OF BACKGROUND SAMPLES)

D=ACTION (TAK=TAKEOFF, LAN=LANDING)

E=FIRST TIME RECORD (DATA TAKING LOCATION ON LANDINGS, AIRPORT ON TAKEOFFS)

F=SECOND TIME RECORD (AIRPORT ON LANDINGS, DATA TAKING LOCATION ON TAKEOFFS)(This is used to estimate the speed of the aircraft)

G=WEATHER CONDITIONS-NAME OF CONDITION (DEGREE) (DEGREES ARE 1-5, 5 BEING THE WORST, EX. P-CLOUDY (4) MEANS IT'S ALMOST CLOUDY.

H=TEMPERATURE RANGE-EST

I=HUMIDITY-EST

J=WIND SPEED-EST

K=BAROMETER-EST

L=dB FILE NAME (go to that file and view it under run #(C)

M=Max Value on dB

N=min value measurement processed from

O=Mean Value on dB

P=Integral from 15dB below max val

Q=data points in integral(if divided by 10, = the time in sec.)

R=Freq Filename

This information is used to do what we do.

Other things we’ll be looking at

With this information, we won’t just be looking at the differences between the integral dB’s of each airplane, depending on weather.We shall also be looking at the difference in frequency between different types of weather, airplane speed, etc.Honestly, we don’t know what all results we’ll be getting from this info, but that is the way the best stuff is discovered, on accident.

For updates on the study, go to our page at http://physics.nku.edu/asg/