DIRAC - Model Type 7841 -Room Acoustics Parameters

All results derive from measured impulse responses of impulsive or continuous room excitation. The hardware required comprises a PC with a sound device, a sound source and a microphone or a sound level meter.

The software works with most Windows-compatible sound devices. A dedicated, ultra-compact USB audio interface (ZE-0948) is also available. For speech intelligibility measurements an artificial mouth-directional loudspeaker sound source such as Echo Speech Source Type 4720 can be used.

• Measure the acoustics of any room, hall or space
• Measure speech intelligibility
• Check acoustics before and after modification
• Compare acoustics of different rooms
• Scale model measurements
• Test and validate sound systems
• Research and education on acoustics
• Troubleshooting room acoustics

• Dual-channel room acoustics
• Compliant with ISO 3382 (room acoustics), ISO 18233 (analysis methods) and IEC 60268–16 (speech intelligibility)
• Quick and easy measurements using an optional calibrated speech source (Echo Speech Source Type 4720)
• Time reverse filtering to measure short reverberation times
• Impulse response editing with unlimited undo
• Auto Measure for large rooms
• Predefined and user-defined parameters
• Auralisation of any sound played in a room, using the room’s impulse response
• Comparisons and statistics of results

Measurements including background noise

DIRAC provides several ways to take the background noise into account. You can measure the speech intelligibility including or excluding the actual background noise. The impact of the background noise can be investigated by mixing a recording of it into the impulse response. Or you can enter a background noise level spectrum.

In combination with the Echo Speech Source Type 4720, DIRAC features the intermittent stimulus. The intermittent stimulus consists of an MLS sequence followed by an equally long period of silence. The full stimulus (MLS + silence) is measured in one pass, and DIRAC extracts the impulse response and the background noise into two separate channels of a .wav file.

Open plan office measurements

For speech intelligibility measurements in open plan offices, the ISO 3382-3 suggests you perform four measurements at each position. With DIRAC 6 you only need a single (system- and level-calibrated) measurement per position.

Using OmniPower Sound Source Type 4292-L or OmniSource Loudspeaker Type 4295, the speech signal levels, impulse response and the background noise levels can all be acquired in a single pass. Plots of the STI vs. source-receiver distance can be created with a few mouse clicks.

With the minimum amount of measurements, DIRAC gives you L_p,A,S, L_p,A,S,4, D_2,S, STI, r_D and r_P.

Two channels for more flexibility
With two input channels, DIRAC lets you double the number of measurements in the same time. Used with an artificial head, you can also measure additional, specific two-channel parameters such as the Interaural Cross Correlation (IACC).

You are in control
DIRAC saves measured impulse responses as standard Windows® .WAV files and includes information for unambiguous identification and interpretation of the data. Extensive signal editing features with unlimited `undo` can be used to extract the relevant portions of an impulse response, or to remove unwanted signals.

Easy reporting
The calculated parameter graphs and tables can be printed or saved as ASCII files that are easily imported into a spread-sheet. The graphs and tables can also be copied to the clipboard, for inclusion in reports.

A user-defined selection of parameters, including group averages and other statistics, can be calculated and saved to disk for all files in a project, in a single operation.

See all data - Continuous MTF graphs
Traditional, modulated, noise-based speech intelligibility measurements contain a limited number of modulation frequencies, so many problems can remain hidden in the coarsely sampled modulation spectrum.

Impulse responses contain the full spectrum of modulation frequencies, and DIRAC 6 has the ability to show them in continuous MTF graphs.

Greater diagnostic power with full STI
The STIPA parameter features prominently in the latest edition of IEC 60268-16. It is described as the preferred parameter for almost all measurement situations. However, the STIPA was originally conceived much like the RASTI as a way to estimate the STI within a reasonable time.

Traditionally, the STIPA is measured with modulated noise. A full STI measurement with modulated noise would take at least 15 minutes. However, by using the impulse response approach, the STI can be measured just as fast as the STIPA. The STI, having many more modulation frequencies in each octave band, has far greater diagnostic power than the STIPA.

DIRAC Room Acoustics Software Type 7841 is used for measuring a wide range of room acoustical parameters. Based on the measurement and analysis of impulse responses, DIRAC supports a variety of measurement configurations.
 
Survey measurements are easily carried out using a small impulsive sound source, such as a blank pistol or even a balloon.

Speech intelligibility measurements can be carried out in compliance with the IEC 60268-16 standard, for male and female voices, through an artificial mouth-directional loudspeaker sound source or through direct injection into a sound system, taking into account the impact of background noise.

With the introduction of DIRAC 6 and the Echo Speech Source Type 4720, speech intelligibility measurements can be performed quickly and easily. The Echo delivers a calibrated signal that is used by DIRAC to calculate different speech intelligibility parameters. The Echo / DIRAC combination also performs well with high levels of background noise.

DIRAC is a valuable tool not only for field and laboratory acoustics engineers, but also for researchers and educational institutions. It has many uses, including measurement of acoustics within any room, hall or space. Users can compare the acoustics of one room with another, validate sound systems and perform scale model measurements.