CARA (Computer Aided Room Acoustics) is a very advanced computer program for computing and optimizing Room Acoustics of arbitrary rooms. CARA is based on the sound source imaging method in combination with a back tracing procedure.

CARA analyzes and improves room acoustic influenced sound coloration in a two step procedure:

• determination of the basic acoustic properties of the room (Acoustic Ambiance) in combination with suggestions regarding the furnishings (wall materials, furniture) in order to linearize the reverberation time spectrum,
• automatic Positional Optimization for the loudspeakers and the listener to minimize sound wave interferences (standing waves) in the listening area.

For a detailed analysis CARA calculates the total sound field data at 1,000-3,000 equally distributed grid points in the room. The evaluation of the sound field data concerns the modal structure (steady state sound pressure distribution), the room response of a Dirac-Pulse excitation in the time domain, the distribution of sound coloration, the sound imaging (stereophonic sound localization), and the speech intelligibility.

CARA provides the expert with a great number of room acoustic reference numbers (frequency dependent reverberation times, sound coloration, speech intelligibility, lateral sound level, or stereophonic sound localization) derived from sound pressure frequency responses or transient room responses/reverberation diagrams.

The special function Auralization renders a listening test in the (virtual) room to evaluate for example sound differences due to different loudspeaker positionings. Any piece of music (two channels Stereo) may be used for this.
CARA is structured into three functional blocks

1. Room Design
2. Room Acoustic Calculations
3. Presentation of Results (2D and 3D Diagrams)

Room Design:

• arbitrary floor plans (L-rooms, coupled rooms, ...), maximum size 100 x 100 m, the wizard "New Room Design" offers a number of predefined floor plan templates (all dimensions may also be entered in non-metric units like inches or feet)
• inside walls as partitions, columns, false ceilings, ceiling beams, as well as sloped ceilings and oblique floors (attic apartments, cinemas)
• furniture database (tables, cupboards, armchairs, etc.), or customize your furniture of several so-called 3D-objects
• additional sound absorbing sub areas (windows, pictures, carpets) can be defined within a wall
• Materials Editor: definition of customized sound absorbing materials
• Loudspeaker Editor: customize your loudspeaker model (cabinet styles : blocks with slanted walls), 1-5 ways loudspeakers, act./pass. subwoofers, or dipole radiating flat panels. Using the updated (Rel. 2.2 PLUS) editor (see Download / Patches) also sophisticated cabinets (e.g. composed of several cabinet sections, like a dipole hybrid LS) may be designed.
• Loudspeaker Configurations: Stereo, Quadro, Surround (analogue, digital: 5.1, 6.1, 7.1, 8.1), PA (Public Address), any number of subwoofers
• loudspeaker database with approx. 200 proprietary speaker models, new models can be "downloaded" from the internet
• Positional Optimization: L-, T-, or cross shaped positioning regions
• walking around in your 3D room model

Calculations:

• automatic positional optimization for the loudspeakers and the listening place, with symmetry constraint options (equal spacing to front and side walls)
• room sound field calculations at 1000-3000 grid points equally distributed within a certain layer above the floor
• reduction of calculating times for rectangular rooms (without furniture) in comparison to the latest version by a factor of up to 1000
• calculation with real and complex reflection coefficients (optionally)
• The additional "PLUS Functions":
  • Calculation and evaluation of the "Acoustic Ambiance" (reverberation time spectrum)
  • Calculation of the high resolution transient room response as a basis for the "Auralization" (listening test)

Presentation of Results:

• representation of the optimized positioning of the loudspeakers and the listening place
• listing of a survey of the room acoustics reference numbers: sound coloration, location, speech intelligibility, reverberation time and lateral sound level
• 3D representation of the frequency and time dependence of the modal structure of the sound pressure in the room
• 3D representation the temporal propagation of the sound wave fronts in the room
• 3D sound coloration, location and speech intelligibility maps of your sound room
• 2D-XY diagrams: sound pressure level frequency responses, location diagram, reverberation diagram, frequency dependence of the mean sound absorption coefficient and of the reverberation time (Sabine, Eyring, Kuttruff and CARA-T10) of your room
• The additional "PLUS Functions":
  • "Acoustic Ambiance" including suggestions for linearizing the reverberation time spectrum by insertion of additional materials or furniture (already during room design)
  • "Auralization": listening tests e.g. for the comparison of different loudspeaker positionings

This overview describes the functions and the procedures of the new release CARA® 2.1/2.2 PLUS. Those who know about CARA® may preferably read the chapters describing the new functions.
In this context we would like to draw your attention especially to the PLUS-Functions:

• 'Acoustic Ambiance': Evaluation of the basic acoustic characteristics of the room and suggestions for improving room acoustics by changing the wall materials or the furniture.
• 'Auralization': Enables you to compare aurally the original sound of a piece of music with its reproduction in the (virtual) room. You may also perform listening test comparing the sound of the loudspeakers placed at different locations in the room.

1. Room Design

   CARACAD is a powerful CAD tool tailored to the task of sound room design. The property sheets 'Floor', 'Ceiling', 'Wall', 'Speaker & Listener', and 'Room' points out an efficient sequencing of the step by step approach for the room design.

   1. Room Basics (Wizard for a new room design)
   2. Change the Floor Plan
   3. Insert Furniture
   4. Material Surfaces
   5. Selection of Materials (Shows the frequency response of the sound absorption coefficients)
   6. Acoustic Ambiance (Evaluation of the basic acoustic characteristics of the room)
   7. Positioning of Speakers and Listener (L-shaped positioning regions)
   8. 3D View of Your Sound Room
   
   

2. Calculations

   CARACALC calculates the acoustics of your sound room. (Calculating times noticeably improved)

   1. Positional Optimization (Symmetry constraints)
   2. Auralization (Listening tests in the (virtual) room)
   3. Sound Field Calculation
   4. Calculating Parameters
   5. Calculation Tracer
   6. Comparison: CARA and Measurements
   
   

3. Results 2D

   Presentation of the results (e.g. of a Special Calculation) is brought up from the calculation module CARACALC. The results are presented by the module ETS2DView.
   For this you click on the menu items Results / Special Calculation to open the results dialog box for 'Special Calculations'. You may select the results for the Total Set of Loudspeakers, for a Loudspeaker Group, or for a Single Loudspeaker.

   1. Frequency Response
   2. Location Diagram
   3. Reverberation Diagram
   4. Frequency Dependence of Reverberation Times
   5. Frequency Dependence of the Averaged Sound Absorption Coefficients
   
   

4. Results 3D

   Presentation of the results of Sound Field Calculations (3D) are also brought up from the calculation module CARACALC. These results are presented by the module ETS3DView.
   For this you click on the menu items Results / Sound Field Calculation to open the results dialog box for 'Sound Field Calculation'. For Sound Field Calculations you decide if the calculations (and the results) shall refer to the Total Set of Speakers, to a Loudspeaker Group, or to a Single Loudspeaker with the start of the calculations. Therefore a respective selection in the results dialog box is not required.

   1. SPL Frequency Dependence (Standing Waves)
   2. Animated Standing Waves
   3. Animated Transient Room Response
   4. Evaluation of Sound Coloration
   5. Evaluation of Stereophonic Sound Localization
   
   

5. Loudspeakers

   1. The CARA Loudspeaker Data Base
   2. Customize Your CARA Loudspeaker Model (New types: dipole radiators and act./pass. subwoofers)
   3. Directivity Patterns of Loudspeakers