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.