If you have installed a sound card in your computer and connected it to e.g. a headphone, you may perform listening tests ('Auralization') in your (virtual) sound room testing different loudspeaker positionings for example.
The Auralization calculations are started from the Calculation menu and result in the
'Transient Room Response' (TRR). The TRR enables CARA to determine room acoustic influenced sound coloration of music reproductions
in the room.
Auralization calculations use a constant frequency step of 0.1 ... 2.5 Hz. This results in a total number of frequency base
points of up to 500,000. In comparison, CARA calculations such as special calculations and sound field calculations are carried
out with a much larger granulation, typically generating only 118 frequency base points using a constant frequency step factor
(logarithmic scaling).
The TRR can be represented and saved for further calculation purposes through the menu Results/Auralization: RIA.
The auralization listening test compares an original piece of music with its loudspeaker reproduction in a room. To create the loudspeaker reproduction of the music, the original music signal has to be mixed with (convoluted by) the transient room response. Both the original music and the new reproduction are saved as wave files to the hard disk. The listening test is then carried out using the ETS Multi Media Player.
Use an original piece of music which meets the requirements of listening tests best. Select a piece which you like most
and which you know very well. That piece of music should provide for a very wideband frequency spectrum (bass, midrange
and high frequencies) being well balanced over the total run time (e.g. jazz, pop or rock music).
The CARA CD-ROM contains the music sample 'Project Online' (C) 1995 SYNTROPOLIS
(www.syntropolis.de) which has been composed, arranged, programmed
and recorded by Bjarne Sommerfeldt and Arne Thomsen.
You may also use the ETS Multi Media Player to compare multiple loudspeaker reproductions. Take the original music sample
and process it using different variations of the same room, such as different loudspeaker positions. Save the processed
signals as wave files and compare them in the player.
The transient room response (TRR) is the sound pressure level at the listening place over time. A single Dirac (or delta)
pulse is transmitted from the loudspeaker(s). Measurements taken at the listening place reflect both the original sound and
the sound reflected (and re-reflected) from walls, ceilings, floors, and furniture.
True Dirac pulses require bandwidth not available to loudspeakers. CARA takes into account the electro-acoustic transformation
by the chosen loudspeaker type in its calculations.
The CARA calculation of the TRR is based on an inverse Fourier transform of the complex sound pressure frequency response of
the total sound field at the listening place.
The TRR diagram shows positive and negative sound pressure amplitudes. Squaring these amplitudes results in the
Reverberation Diagram comparable to a high resolution version created via a special calculation.