Mr. Paul E. R.Packbier
PCR Environmental, Inc.
222 Duenas Drive
Tamuning, Guam 96911

Re: Results of 24-Hour Measurements
LSG&A File 00071

Dear Mr. Packbier:

LSG&A has completed hourly measurements of the A-weighted sound levels at three locations near the AB Won Pat Guam International Airport, over a 24-hour period. LSG&A is pleased to submit this report which summarizes the results of the sound level measurements and the calculation of the existing DNL sound levels. The measurements were made in order to document the existing sound pressure levels at the three residential locations.

The results of the measurements indicate that the existing DNL sound levels at the three measurement locations near the Guam International Airport, Locations 1-to-3, are 60, 71, and 53 dB(A), respectively.

1.0 MEASUREMENT LOCATIONS

The 24-hour sound level measurements were measured at three locations near the airport. The measurement locations are described below in Table 1.

2.0 DATA ACQUISITION AND ANALYSIS

2.1 Data Acquisition

The sound levels at the three locations were measured for a period of 24 hours, beginning at 4:00 PM on 28 August 2000. The equipment used for the 24-hour measurements are summarized in Table 2.

In addition, short duration sound pressure level measurements approximately 35-to-45 minutes in length, were performed at the beginning, and middle of the measurement periods at each of the three locations. The short duration measurements of the airborne sound pressure levels were performed using digital audio tape recording (DAT) data acquisition system. The system consisted of a Type 1 Brüel & Kjær Model 2236 precision sound level meter, with a Model 4188 microphone providing calibrated input to a Sony TCD-D7 digital audio tape recorder. The system was calibrated before and after the measurements using a Brüel & Kjær Type 4231 acoustical calibrator. The sound level meter was set on a tripod at a height of approximately 5 feet for each measurement.

The meteorological conditions during the measurements are listed in Table 3. Acoustical measurements are not made during periods of precipitation, or when continuous wind speeds exceed 10 miles per hour. Although meteorological data were measured at only one of the locations, the meteorological conditions at each location were assumed to be the same.

2.2 Data Analysis

The results of the 24-hour measurements were returned to LSG&A's laboratory and downloaded to a computer and transferred to a spreadsheet program for analysis. The hourly A-weighted sound levels were used to calculate the DNL at each location. Note, that the sound level meter used at Location 3, did not print out the hourly Leq sound level data. The 24-hour statistical sound level data at this location, as well as the Leq data of the short duration measurements, were used to estimate the DNL sound level at this location.

The tape recorded data were analyzed in LSG&A's laboratory using the firm's computer-controlled real-time, acoustical data analysis system. The data analysis system provides statistical octave-band, one-third octave-band, and A-weighted sound levels for the measured data.

3.0 RESULTS AND DISCUSSION

Table 4 shows the Leq results of the 24-hour measurements at Locations 1 -to- 3, and the calculated DNL. As previously mentioned, the values for Locations 1 and 2 are the actual measured data, and the values at Location 3 are estimated based upon the statistical sound level data and from the short duration octave-band sound-pressure level measurements.

Figures 1 through 3 show the Leq results of the short duration octave-band sound-pressure levels measured on 28 and 29 August 2000, at Locations 1 through 3, respectively. Please note, that several short duration noises, uncharacteristic of the area at Location 3, occurred during the early morning measurement period. Therefore, a 15 minute section of the full 45 minute measurement period, containing only characteristic sounds and including several aircraft, was analyzed in order to provide a Leq more characteristic of the area.

Figure 4 shows the three measurement locations during the 24 hour period from 28-to-29 August 2000, and the commercial only aircraft DNL noise contours from the 1978 AIR Installations Compatible Use Zones U.S. Naval Air Station Agana report, prepared for Department of the Navy. The figure shows that DNL at Location 1 would be slightly below a DNL of 65 dB(A), Location 2 would be between a DNL of 70 dB(A) and 75 dB(A), and Location 3 would be below a DNL of 65 dB(A). The results of the measured DNL for the 24-hour period on 28-to-29 August 2000, for Locations 1-to-3 were 60 dB(A), 71 dB(A), and 53 dB(A), respectively, and therefore ,agree with the results of the 1978 report.

I trust that this is sufficient for your present needs. Please call me if you have any questions regarding this information.

Very truly yours,

LEWIS S. GOODFRIEND & ASSOCIATES

Joseph F. Horesco
Staff Engineer

JFH:ck
Enclosure

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