Handbook for Sound Engineers

Computer Aided Sound System Design 1381

The real-time ability of the measuring system is based
on very high refresh rates for the calculation of results
and their display and analysis—approximately 10/s.
One can understand such a measuring system also as
an “oscilloscope for room impulse responses.” Possible
changes of the acoustic behavior may be seen immedi-
ately and directly.
In Fig. 35-57, the excitation is done with noise,

sweep, or MLS. In live situations this will be quite often

annoying and cannot be done under all circumstances.

So the next step is to use running music or speech

signals as excitation signals and to derive impulse

responses. Fig. 35-58 shows a block diagram for such a

tool usable with natural signals like music or speech and

in Fig. 35-59 the graphic user interface of EASERA

SysTune^58 is shown, a tool that allows such a kind of

measurements.

Once the IR has been computed in either a dynamic

or static manner, electroacoustic and room-acoustic

measures can be derived from it, such as the RT 60 , D/R

ratio, C50, or STI. These values can then be compared

with the modeling results.

Figure 35-55. AURA presentations in EASE 4.2.

Figure 35-56. Block diagram of a modern software-based
four-port measurement tool including the needed AD/DA
convertor.

A. C80 presentation.

B. Articulation Loss AlCONS presentation.

Figure 35-57. Static type of FFT-based measurements.

Figure 35-58. Dynamic (continuous) type of FFT-based

measurements.

Figure 35-59. Graphic user interface of EASERA SysTune.