Using Audio Coverage Uniformity
Audio Coverage Uniformity, or ACU, is a test methodology based on ANSI/INFOCOMM standard A102.01:2017, Audio Covered Uniformity in Listener Areas.
ACU can be used to determine how evenly a sound system covers a venue.
Please see the standard for full information on performing the test.
This document is only intended to describe the use of the ACU test
module obtain the results needed for an ACU test. Many topics, such as
determining the number and location of tests is covered in detail in
the specification.
In general terms, the test involves
measuring the ambient noise level in the space, and then test the sound
system SPL level in octave bands at a number of locations.
ACUML
This acronym is for Audio Coverage
Uniformity Measurement Location, and refers to the places at which
sound system SPL measurements are taken.
Settings
Tap the wrench icon to bring up the
Setup page.
Choosing the Method
Using the control, tap to select between Limited Bandwidth and Full Bandwidth
Limited Bandwidth
This mode covers 6 octave bands, starting from 250Hz.
Full Bandwidth
The Full Bandwidth test covers 8 octave bands, starting from 125Hz.
Number of Tests
The number of tests required is called out
in the specification, and will vary depending on a number of factors.
Once you have determined the number of tests to run, use the +/-
control to set the number of tests.
Auto Advance
Since there may be numerous locations to test, turning on
Auto Advance will save time, since the current test number is
incremented as soon as the test is completed.
Input Source
You can select the audio input source using this button.
Mono / Balanced
If you have a pseudo-balanced output adapter, select Balanced.
Otherwise, select Mono, which presents the same phase signal to both
right and left output channels.
Operation
Ambient Noise Levels
From the main screen, select Ambient on the mode control, and tap the
Play/Pause button on the lower left to start the octave-band
filter-based RTA running. When the display has stabilized, pause it, or
switch to the next step.
ACUML Tests
Tap the mode control to select ACUML tests. For these tests, you will
need to route the output of the device to the input of the sound
system. You can do this with a 3-conductor wire plugged into the
headset jack, using our iAudioInterface2 or iTestMic2 output, or by
using a low-latency wireless link.
After verifying that the levels are correct, tap the Play/Pause button
on the lower left to begin a test. A short sweep (chirp) will play, and
the analysis will proceed immediately. The results for this location
will appear on the screen.
If Auto-Advance is turned on, the test will increment on the screen, so
you can move directly to the next ACUML and run the next test there.
You can manually increment or decrement the test number at any time,
and if you tap the icon between the + and - buttons you can select any
particular test, for example to replace the results with a new test,
and if you tap the small "i" on the right you can name the ACUML.
You can also view an average of all tests, and clear the entire test
batch to start over. This also clears the Ambient Noise test.
Results
When you have completed all of the tests, tap the mode control to change to the Results screen.
The calculations will be completed, and all of the test results will
appear. You can scroll this page up and down to see all of the results,
including the system classification.
Saving and Recalling Files
To save the current test results of ACU, tap the folder icon on
the lower left side of the toolbar on the bottom of the screen. This
will being up the Save / Recall page.
Save the file by entering a file name and tapping Store File on the the popup that appears.
To recall a stored file, select it from the list to highlight it, and
then tap Recall to bring up the results. Note that recalling a stored
file will replace the current test data.
After recalling a test, you can continue the test, by pressing the Play/Pause button to start the test running.
To clear a recalled test, press the Stop button.
When you save the file, the app stores all of the current values, and
it also stores a list of minute-by-minute values that include the Leq
over the minute, and the Peak value reached in that minute. The filter
setting of the SPL meter (Z/A/C) is used for these calculations.
These values are saved in the .txt file, which may be opened in Excel
or Numbers.
Screenshots
Tap the screen shot button on the upper right toolbar to save an image of the test in your photo roll.
As with all iOS apps, you can take a screenshot of the entire screen by
simultaneously pressing the Home and Power buttons on the device. The
image will then be in your photo roll.