2. USING THE TNM VERSION 2.5 LOOK-UP TABLES SOFTWARE

This section provides the hardware and software requirements, installation instructions, and how to operate the accompanying computer program.

2.1 System Requirements

The system requirements for TNM Version 2.5 Look-Up Tables are:

Microsoft® Windows 98/NT/2000/XP
200 MHz Intel® Pentium or equivalent
32 MB of RAM
20 MB of available hard-disk space for installation
Monitor resolution set to 1024 x 768 pixels or higher

2.2 Installation

To install FHWA TNM Version 2.5 Look-Up Tables:

Download the Look-Up Tables "Setup.exe" file from the TNM website: http://www.thewalljournal.com/a1f04/tnm.
On the Windows taskbar, click [Start] and select Run.
Click [Browse]. Navigate to the Setup.exe file.
Double-click on Setup.exe and follow the onscreen instructions.
The program will create a shortcut icon on your desktop (see Figure 2). Double-click on the shortcut icon to run the program.

This figure shows the shortcut that is placed on your desktop when you install TNM Look-up. The shortcut is two cars with an arrow and the words "TNM Lookup" underneath.
Figure 2. Desktop shortcut.

2.3 Computing Sound Level Results

2.3.1 Metric/English Units

Once the program is started, the user is prompted to select Metric or English units for input and computed results. Note that the results contained within the Look-Up Tables were computed in TNM using Metric units. Therefore, if the user chooses English units, a hard conversion (1 m = 3.281 ft, 1 km/h = 0.621 mph) is performed on all parameters to obtain the Metric-to-English units, rounded to one decimal point. Click [Ok] once you have made your selection.

This figure is the initial screen that appears when you run the TNM Lookup program. It has "File" and "Help" in the toolbar and a "Units" box where you can select "English" or "Metric", then hit "OK".
Figure 3. Metric/English units selection.

Note: If a parameter is unintentionally selected at any time, the user can reset the parameters to start over. To do this, select the File menu and click on Reset as shown in Figure 4.

This figure is showing that you can use the "File" dropdown bar to either "Reset" your input parameters, or "Exit".
Figure 4. Reset function.

2.3.2 Barrier Information

Select if there is a noise barrier present and click [Ok].

If "Yes" is selected, additional parameters will appear (See Figure 5). Select the distance between the barrier and the centerline of the roadway (10 or 30 m if you have selected Metric units / 32.8 or 98.4 ft. if you have selected English units). Select the desired barrier height (between 2 and 10 m if you have selected Metric units / between 6.6 and 32.8 ft if you have selected English units).

Note: The program will not interpolate between whole integer heights (e.g., 2.5 m); however, the user may estimate the sound levels for intermediate heights by using the general rule-of-thumb that once the line of sight between source and receiver is impeded by a barrier, a 1-m change in barrier height typically equates to a 1.5-dB change in sound level. Click [Ok] once you have completed selecting your barrier distance and height (if a barrier is present).

This figure is a screen shot of the TNM Lookup program. It is highlighting the "Barrier Information" input box. This box asked if a noise barrier is present or not, and if it is the distance between the center of the roadway and the noise barrier in meters. It also asks for the barrier height in meters.
Figure 5. Noise barrier parameters.

Note: The included barrier is of infinite length and placed parallel to the roadway (see Figure 1).

2.3.3 Terrain Surface

Next, choose whether the terrain surface between the source and the receiver is acoustically hard or acoustically soft.

Note: Acoustically hard terrain is defined as any highly reflective surface in which the phase of the sound energy is essentially preserved upon reflection; examples include water, asphalt, and concrete. Acoustically soft terrain is defined as any highly absorptive surface in which the phase of the sound energy is changed upon reflection; examples include terrain covered with grass, dense vegetation, or freshly fallen snow.

This figure is a screen shot of the TNM Lookup program. It is highlighting the "Terrain Surface" input box. With in this box you can select either "Hard (Pavement/Water)" or "Soft (Lawn)".
Figure 6. Terrain surface parameters.

Note: For propagation over acoustically hard ground, an effective flow resistivity of 20,000 cgs rayls was assumed; for propagation over acoustically soft ground, an effective flow resistivity of 300 cgs rayls was assumed.

2.3.4 Traffic Information

Enter the vehicle volume information in vehicles per hour between 0 and 99999 and also the vehicle speed information ( between 0 and 130 km/h if you have selected Metric units / between 0 and 80.7 mph if you have selected English units) as shown in Figure 7.

This figure is a screen shot of the TNM Lookup program. It is highlighting the "Traffic Information" input box. This box asks for the volume (in vehicle per hour) and speed (kilometer per hour) for automobiles, medium trucks, heavy trucks, buses and motorcycles.
Figure 7. Traffic Volume and Speed Parameters

2.3.5 Receiver Information

Enter the receiver distance information by clicking the [Add] button inside the "Receivers" box. Enter the distance of the receiver from the centerline of the roadway (between 10 and 300 m if you have selected Metric units / between 32.8 and 984.4 ft. if you have selected English units). TNM Version 2.5 Look-Up Tables does not allow a receiver to be placed at the same distance as the barrier (e.g., a receiver distance of 10 m is not allowed when the barrier is also at 10 m). The user can also include a single line description for each receiver by entering text in the "Description box".

Note: All receivers are set at a height of 1.5 m above the ground and placed at user-input offset positions perpendicular to the roadway.

This figure is a screen shot of the TNM Lookup program. It is highlighting the "Receivers" input box. You are able to type in a description for up to 45 receivers, with a distance in meters from the centerline.
Figure 8. Receiver Description and Distance Parameters

Additional receivers can also be added by clicking on the [Add] button inside the "Receivers" box (see Figure 9). TNM Version 2.5 Look-Up Tables can calculate sound levels for up to 45 receivers simultaneously. If a receiver is unintentionally added, you can remove it by clicking on the [Remove] button. This will remove the most recently added receiver to the list.

This figure is a screen shot of the TNM Lookup program. It is highlighting how you can add additional receivers. You are able to add or remove receivers by selecting the appropriate "Add" or "Remove" buttons.
Figure 9. Entering Additional Receivers

2.3.6 Run Calculations

Once the above parameters are entered into the program. The [Run] button changes from a red button to a green button (see Figure 10). This is an indication that the program has the necessary parameters to calculate sound level results.

This figure is highlighting the "Run" button on the bottom of the TNM Lookup program.
Figure 10. Run calculations button.

Click on the [Run] button to compute sound levels. An output file consisting of the input parameters and computed sound levels will pop up (See Figure 11).

This figure is a screen shot of the "Case Results Output Display". The top portion is a summary of the inputted Traffic Volume/Speed Information; the middle section is a summary of the Barrier Information and Terrain Surface Information. The bottom section is the summary and results for the receivers that you inputted. There is a "Save" or "Close" button at the very bottom of the screen shot.
Figure 11. Case Results Output Display

The hourly-equivalent sound level (1hEQ denoted by the symbol, LAeq1h, also often referred to as LEQ) at each receiver is computed and displayed. If a barrier were present, then the LAeq1h computed at the receiver behind the barrier, as well as the barrier insertion loss, i.e., the difference in level before and after installation of a barrier, is computed and displayed.

Note: LAeq1h is defined as ten times the base-10 logarithm of the square of the ratio of time-mean-square, instantaneous A-weighted sound pressure, during one hour, divided by the squared reference sound pressure of 20 :Pa, the threshold of human hearing.

The output can also be saved as an ASCII text file by clicking on the [Save] button. The program will then prompt you to enter a name for the file and select the directory to save it in. A comment for the case can be entered into the output box. The case comment will be saved directly to the output file. The program will then confirm the file has been saved (see Figure 12).

This figure is highlighting the confirmation box the pops up when you select the "Save" option indicating that your case file has been saved.
Figure 12. Confirmation of saved output file.

The output file can be closed by clicking on the [Close] button. The user may return to the program to change barrier distance, barrier height, terrain surface, vehicle traffic, and receiver parameters. TNM Version 2.5 Look-Up Tables allows the user to adjust the aforementioned parameters and recalculate runs without restarting the program. However, note that when the barrier distance is changed, invalid receiver distances (e.g., receiver distance of 10 m when the barrier distance is also 10 m) will have 0.01 m (0.01 ft. if using English units) automatically added to the distance.

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To provide Feedback, Suggestions or Comments for this page contact Mark Ferroni at Mark.Ferroni@dot.gov.