BaseOps User's Guide, Chapter 11: Setting Weather Conditions

Weather conditions are an important part of a BaseOps case. Temperature, relative humidity, and atmospheric pressure strongly influence the absorption of sound by the atmosphere. This in turn influences the noise levels throughout your area of interest.

To set your case's weather conditions, first choose Weather from the object type selector dropdown list. Then set the weather conditions in the text pane.

You have two choices for how to specify weather conditions.

Use these weather conditions

Type the temperature, relative humidity, and atmospheric pressure that will be used when calculating noise levels.
Pick weather conditions from monthly averages

Type the average temperature, relative humidity, and atmospheric pressure for each month. BaseOps will then calculate the 1,000 Hz atmospheric sound absorption coefficients for each of the 12 months, and pick the weather conditions associated with the sixth smallest coefficient. An arrow <== indicates the selected month.

Sound absorption coefficients are calculated using the method given in ANSI S1.26-1995 (ASA 113-1995), "Method for Calculation of the Absorption of Sound by the Atmosphere". Typically, you will not need to concern yourself with these calculations. However, BaseOps provides a tool that you can use, if necessary, to manually calculate sound absorption coefficients. Choose Sound Absorption Coefficient Tool from the Tools menu. The Sound Absorption Coefficient Tool dialog box appears.

Type the desired weather conditions and sound frequency. The corresponding sound absorption coefficient is automatically calculated and displayed.

Important:

Atmospheric pressures that you supply to BaseOps should not be sea-level corrected.

Note:

You can select the units used to specify temperatures, atmospheric pressures, and sound absorption coefficients. See Setting the Case's Physical Units for more information.