FFT has an “Avg” or Average mode that can be selected by tapping the control in the lower right corner. Selecting Avg starts a mode where FFTs run continuously, and the results are averaged (using dB logarithmic averaging) until you tap the Play/Pause icon, which pauses but does not clear the results, or the Reset button in the Average control box.

Thus, you can position the microphone in one location, average for 10 seconds (for example), tap Pause, move to another location and restart the average, and repeat this as much as needed. The resulting graph is the true average of the results in each location.

Sometimes, however, you may want to combine the results of several saved tests. This can also be done, by following these steps.

This procedure assumes that you have already stored several tests, using the normal Save/Recall tool.

• Turn off the audio input. Tap the settings icon (wrench), tap the microphone icon on the top right, and select the Disable Audio Input choice. Tap Done. 
• Turn on Average Plots. On the Settings page, turn on the Average Plots switch.
• Recall the tests. One by one, recall each saved test by tapping the Save/Recall icon and selecting each the tests you want to average, one at a time, and tap Recall. You will see the plot change as each recalled test is averaged into the plot.
• Save the average. Now that you have the average of the tests on the screen, and audio input disabled, go to Save/Recall and store this test as you did with the other tests. The average plot will be stored, and you can now turn off Average Plots, and see each test and the average at the same time on the screen.