Audio Interface Types¶
An audio interface is a device used to stream audio in to and out of a PC. It could be either a USB device or a Dante audio-over-Ethernet network.
A USB audio interface typically includes all components in one box: microphone preamplifiers, audio inputs and outputs, and a headphone amplifier.
A Dante network uses a standard computer network to connect separate audio components. Please see Revision 3 Kit for an example of a Dante network used with IRIS.
IRIS software requires an audio interface with ASIO drivers. Standard windows audio drivers are not supported.
IRIS operates at either 44.1 kHz or 48 kHz sample rates.
3D Microphone Array¶
For measurements with a 3D microphone array, the interface requires:
- Four analog microphone preamplifier inputs with digitally controlled gains (typically XLR connectors).
- The four inputs must be matched to within 0.1 dB. It is recommended to calibrate the audio interface to ensure this precision of matching.
- Phantom power (+48 V) on each microphone input.
For mono measurements, one microphone input is required. Check the hardware requirements for the specific microphone you intend to use.
A digitally recallable microphone preamplifier gain must be used for mono measurements which rely on a calibrated system (e.g. sound strength or open plan office measurements).
One line-level output is required to connect to the source loudspeaker.
The connection from the output to the loudspeaker amplifier should be balanced, using an XLR or TRS connector. Balanced lines carrying differential signals are less susceptible to external interference and noise than an unbalanced/single-ended connection.
It is recommended that the audio interface includes a headphone amplifier to enable monitoring of the microphone signals over headphones. This is especially helpful when diagnosing issues with hardware or power on site.
An optional loopback connection is required for automatic source-receiver distance measurements when using a USB audio interface. This requires one additional input and output, and maybe an analog or digital connection. This is necessary due to non-deterministic latencies in the USB audio stream.
Dante networks have a fixed time delay and do not require a loopback connection to measure source-receiver distance. Any latency present in a Dante system is automatically handled by IRIS software.
Automatic source-receiver distance measurements require line-of-sight between the source and receiver.