3D acoustic impulse response - measurement and visualisation

IRIS is a powerful and user friendly measurement system for capturing and analysing room impulse responses in 3D.

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System overview

The IRIS Plot

The IRIS Plot

The IRIS plot is at the heart of the IRIS system. Sound rays arriving at the measurement position are represented as a series of easy to identify coloured spikes, immediately after the measurement is conducted.

The IRIS plot can be used to relate sound rays to physical features of the room, observe the directional distribution of early and late sound energy, as well as identify surfaces causing problematic reflections.
It’s simple to understand:

  • the spike direction tells you where the ray has come from
  • the spike length tells you the strength of the ray
  • the spike colour tells you when the reflected sound arrived at the microphone
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3D Impulse Response Capture

3D Impulse Response Capture

The IRIS measurement system utilises a first order Ambisonic microphone array, which is placed at the desired receiver position. The room is excited by a loudspeaker at the source position, driven with a single swept sine stimulus. The IRIS software provides the stimulus, records the room’s response and processes and visualises the results immediately.

Custom adapter boxes have been designed to simplify the measurement system and a single ethernet cable is used to transfer the microphone signals. 

IRIS accurately captures how the room’s surfaces direct sound to the receiver position in 3-dimensions.  The 3D image plot displays the measurement via the easy-to-use interface.  

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The graphical nature of the IRIS plot allows for efficient visual comparison of the acoustical properties at different seats within a room, or between different rooms.

IRIS is an excellent problem solving tool allowing a room’s acoustic anomalies to be easily identified. For example IRIS can be used to identify late reflections, or to identify seats lacking in early or lateral energy.  The effect of specific reflective or absorptive surfaces within the room can be identified.


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For a newly constructed space, IRIS can measure an extensive range of room acoustic parameters from ISO 3382:2009-1 with the added benefit of a 3D plot that can be used to verify the early reflection pattern is what was designed.

Numerical magnitude, direction and time information may be obtained for each ray for a comprehensive analysis. 

Clicking on any point of the impulse response waveform will identify the corresponding spike on the IRIS plot, allowing for quick and easy identification of where that sound has come from. Conversely, rays selected in the IRIS plot are also identified in the impulse response waveform.

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What people are saying

  • The operation and configuration of IRIS is effortless...

    Sebastià V. Amengual Garí
  • The success of a musical performance depends on the sense of proximity of performer to listener. This sense is mediated largely by the directional properties of the reflected sound field.

    Sir Harold Marshall
  • Marshall Day Software is like having an acoustic laboratory in the palm of your hand.

    Associate Professor Yan Xiang, Tsinghua University