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Sound Source

IRIS generates a sweep excitation signal to be played through a loudspeaker. External excitation (e.g. an impulsive source) is not currently supported.


The source includes the loudspeaker and power amplifier. Powered loudspeakers have a power amplifier built inside the loudspeaker enclosure.

Omnidirectional Loudspeakers

Measurements following ISO 3382-1, 2 or 3 require an omnidirectional source. Refer to these standards for details.


It is highly recommended you drive an omnidirectional loudspeaker with a power amplifier which has recallable gain (e.g. a fixed or digitally controlled gain). This is a requirement for measurements which depend on a calibrated output level e.g. sound strength or open plan office measurements.

Other Loudspeaker Types

It may not be appropriate to use an omni-source in some situations. Consider how sound is typically generated and heard in the space being tested. For example:

  • For measuring speech intelligibility, it may be necessary to use a source which mimics the directivity of a human talker.
  • A control room or post-production studio. Connect the output of IRIS directly to the installed studio monitors.
  • Investigating an echo in a large auditorium which is excited by the installed sound system.
  • Assessing a room’s response to a type of loudspeaker. For example, IRIS could be used to compare the performance of a basic loudspeaker box to a steerable column array in a highly reverberant space.

Loudspeaker Cabling

The loudspeaker cables required depend on your specific loudspeaker and audio interface. A power amplifier or powered loudspeaker will typically take a balanced line input over a TRS or XLR connector. Similiarly, most audio interfaces will send balanced audio out through a TRS or XLR connector.


It's important you use the correct type of cable (balanced or unbalanced) with your measurement equipment. If you are making calibrated measurements, ensure you always use the same type of cable otherwise the level may change at the loudspeaker.