Room Treatment
This document describes how to use the Room Treatment module.
The Room Treatment app by Studio Six Digital is designed to provide assistance in measuring the RT60 decay times for a room and in
selecting and applying acoustic room treatment materials, such as sound
absorption panels and wall treatments to correct excessive room reverberation times.
The app is meant as an aide to estimating material requirements for a
room, but is not meant to replace the services of a trained
professional consultant. Actual conditions vary widely, and although
the app will help you predict the affects of adding different types of
room treatments, you should always check with a pro before committing
time and resources to a project.
RT times for small rooms are particularly difficult to measure and
predict. Take care in interpreting the results from smaller spaces.
All calculations used by the app
conform to ANSI and ISO standards for computing RT60 time, and for
applying the specified material absorption coefficients. The app measures RT60 times in
the 63Hz to 8000Hz octave and 1/3 octave bands. Also, the Overall decay
time is computed from the 4 octave bands, 250Hz to 2000Hz.
See the section at the bottom that explains the calculations that we
are doing to arrive at the RT60 times and affects of materials.
The Main Screen
The main screen
consists of the Decay Time window, the Room window, and the Materials
list. There is a toolbar at the bottom of the screen, which includes a
button to save the data or recall previously saved room data, and there
are control buttons at the top. There is also a cursor that may be
dragged across the plot to read out any specific value.
Room Window
The user may begin by entering the room dimensions, in either feet or
meters, depending on the global units setting (General settings
screen). The room volume will be computed from these dimensions.
Next, a room type is selected and a target RT60 time will
be shown, based on an industry standard algorithm for the selected room type.
Decay Plot Window
The Decay Plot window shows the results of the RT60 test. It will also
show the affects of the materials, if "Correct" is selected. You can
drag a cursor across this screen to read out specific values.
Depending on the iOS device orientation, and the available screen area,
the bars on the Decay Time plot may be labeled with the decay time and
frequency. On iPad, both the octave and 1/3 octave bands will be
labeled if the device is held in landscape mode.
The Decay plot can be shown in Octave, 1/3 Octave, or Overall (wide band) modes.
Also, the effects of the room treatment materials may be turned on or
off, to compare the difference in RT60 time with and without the
treatment being applied.
Materials Window
This window displays a scrolling list of all of the materials that have
been selected for the room. To edit this list, tap the Materials button
on the lower toolbar.
The RT60 Decay Test
To begin the Decay Time calculation, the tap the RT60 button on the bottom of the screen. The Decay Test screen will appear.
To measure decay, the app requires an impulsive sound. This would
typically be achieved by popping a balloon in the room, or in a very
large room possibly by firing a starter pistol. A solid handclap may be
used if nothing else is available.
Stand back about 3 feet (1 meter) from the iOS device microphone when you are creating the impulse.
The internal mic on the iOS device is adequate for these measurements.
The test is very simple. Press the Record button, and a 5-second
countdown timer will appear. The recording starts at the one second
mark, and you may create the impulse any time after that. After the
sound decays for a few seconds, tap the Stop button to stop the test
and end the recording.
Press Done to return to the main screen.
Materials
The
app has the ability to compute the effects of applying acoustical
treatment materials to the room. As a material is applied, the change
in decay time is shown graphically, in real time. Thus, you can add or
remove room treatments and watch the effects on the Decay Time plot.
To apply an acoustical treatment, tap the Materials button in the
bottom toolbar. A list of all of the groups of materials will be shown.
Tap a group name to see all of the materials available within that
group.
To add a unit of acoustical absorption material, tap the + on the stepper. You may add any quantity of a material.
The changes in RT60 times will be shown in real time on the decay plot.
Save / Recall
Tap the
folder icon to bring up the Save / Recall screen. You can save the room
data here, which will include the room dimensions, RT60 decay times,
and all of the materials that you may have selected for the room.
All of the normal Save / Recall features are available.
Calculation Methods
The measured RT60 times use the engine from our Impulse Response
module, and thus will normally be accurate, as long as the impulsive
sound is wide-band, such as from a balloon pop.
The Room Treatment app uses the best available estimation methods other
than doing a full ray-tracing analysis of the space. We use a modified
version of the Eyring Method, known as the Millington-Sette equations.
This method is based on the Eyring equation, which is much more
accurate than the Sabine method on non-highly reverberant rooms. works
best when the boundaries (walls, floor, and ceiling) are evenly
diffuse. The prediction methods will also work much better in larger
rooms.
The target RT60 value is computed, based on the volume of the room and
the room type. Rooms used for performances will typically work best
with longer RT times.