**6. Introduction to application: Acoustics based optimization in multimedia classroom**

218 Stochastic Modeling and Control

for Room 1 is:

Rating: FAIR,

and for Room 2:

STI = 0.5044 (male), 0.4893 (female),

%ALcons= 8.8092; RASTI = 0.5146 Rating: FAIR, %ALcons = 10.4877,

STI = 0.6668 (male), 0.6362 (female) Rating: GOOD, %ALcons= 3.2315; RASTI = 0.7269 Rating: GOOD, %ALcons = 3.3203.

correlation between the results is very good.

**4. Objective measurements of room acoustic quality parameters** 

**Table 2.** Objective measurement results for Room 1, sweep signal, sampling f = 48 kHz

Measured speech intelligibility (sweep signal, sampling f = 16 kHz)

**5. Statistical based analysis - first conclusion** 

Since it largely depends on the audience and their real possibilities of making assessments, subjective evaluation of room acoustic quality parameters is always difficult to make, as well as to accurately assess the subjective room quality. The resulting dispersion of the

Objective measurements for Room 1 and Room 2 have been made with acoustical SW "ARTA". The measurements were done with 4 kinds of signal generator: sweep, pink noise, white noise and MLS. The sampling frequency was 48 kHz except for the speech intelligibility measurements, where the sampling frequency was 16 kHz for all signals. The

f [Hz] T30 [s] T20 [s] T10 [s] EDT [s] C80 [dB] C50 [dB] D50 [%] 63 1.268 1.344 0.877 1.608 1.79 1.12 56.40 125 1.197 1.326 1.182 1.491 0.80 -3.17 32.50 250 1.027 1.165 1.305 1.400 0.58 -1.73 40.20 500 1.164 1.237 1.260 1.429 -0.51 -3.06 33.09 1000 1.139 1.240 1.100 1.315 1.61 -0.61 46.52 2000 1.059 1.101 1.114 1.170 2.30 0.00 50.01 4000 0.873 0.852 0.799 0.904 4.50 1.55 58.86 8000 0.710 0.694 0.697 0.699 6.82 3.35 68.38

Acoustics is a characteristic of a room where within that space sound is well transferred and well received (heard) according to the type of sound (speech or music, that is type of music) and purpose (listening or recording). The development of acoustics – acoustic science, and especially its sub disciplines, architectural acoustics, is based on defining objective parameters of acoustic quality of a space and in finding methods for their measurement and establishment of their interdependency with subjective parameters of spatial acoustic quality which were obtained through subjective testing. The traditional task of spatial acoustics was to ensure and form conditions which will enable better acoustic transfer from the sound source to the listener. Objective parameters of spatial acoustic quality are determined by the possibility of finding objective methods of measurement. The parameters that determine the acoustic quality of a room are: time of echo, time of early drop of sound energy, room constant, room radius, clarity, mean time, definition, relationship between the reflected and direct energy, support, relative level or power index, sound color, occasional diffusion, the assessed relationship signal/murmur, loss of consonant articulation, speech transfer index, the ratio of useful and harmful sound, fraction of lateral energy, inter-aural coefficient of cross correlation, direction index, and time of initial delay. All measurable parameters of acoustic quality of a room which are interrelated in some way due to the fact that they have basic characteristics of sound waves are mentioned here. It is not necessary to measure and use all parameters in spatial acoustics. Those which can be measured and those that give us reliable information even with subjective parameters on the acoustics of the room being tested should be selected. The results obtained will help take appropriate actions which will improve the acoustic quality of a particular area. Subjective parameters for acoustic quality of a room depend on whether we are referring to speech or music. When determining the acoustic quality of a room with respect to speech the subjective parameter is intelligibility. Subjective parameters for the acoustic quality of a room are: loudness, definition or clarity, reproduction of high frequencies or brilliance, reproduction of low frequencies or fullness, sparkle, sound imagery (stage), localization or locating the sound source, intimacy or closeness, echo, noise level, reverberation, tone reproduction, color of voice, tone or sound, intelligibility of speech, spectral equality, dynamics, area of soundness and transient response, deformities, equal distribution of sound pressure, reproduction of ambiance, spatiality, impression of space, diffusion, resonance audibility and entire acoustic impression.
