Type 7841

DIRAC - Room Acoustics Software

Software to measure room acoustical parameters in the field or laboratory according to ISO 3382 (room acoustics), ISO 18233 (analysis methods) and IEC 60268-16 (speech intelligibility).

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DIRAC is a valuable acoustics measurement tool for field and laboratory acoustics engineers, researchers and educational institutions. Users can compare the acoustics of one room with another, validate sound systems and perform scale model measurements.

Based on the measurement and analysis of impulse responses, the tool supports a variety of measurement configurations.


  • 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

DIRAC supports wireless room acoustics measurements when connected to HBK 2255 Sound Level Meter as a wireless microphone, and/or HBK 2755 Smart Power Amplifier as a wireless sound source. Multi-channel measurements can be made using multiple HBK 2255’s, or with most Windows compatible multi-channel sound devices.

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.

In combination with 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 takes into account background noise levels.

Using OmniPower Sound Source Type 4292-L, 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 Lp,A,S, Lp,A,S,4, D2,S, STI, rD and rP.


  • Multi-channel room acoustics
  • Compliant with ISO 3382 (room acoustics), ISO 18233 (analysis methods) and IEC 60268–16 (speech intelligibility)
  • The convenience of fully wireless measurements with HBK 2255 Sound Level Meter and HBK 2755 Smart Power Amplifier
  • Quick and easy measurements using an optional calibrated speech source (Echo Speech Source Type 4720)
  • Real-time frequency analyzer with spectrum freeze, max-hold and user-defined reference curves
  • 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