Source Selection and Directivity

The choice of source depends on the measurement objective:

Room characterization: Omnidirectional source (dodecahedral speaker) per ISO 3382-1 requirements. This captures the room's response independent of any particular loudspeaker system.
System alignment: Use the actual installed loudspeaker system. This captures the combined response of the loudspeaker directivity and room acoustics — what the listener actually hears.
Auralization: Omnidirectional source for flexibility in post-processing directivity patterns.

Source Height and Position

For room characterization, AES-2id recommends source height of 1.5 m (standing head height) placed at positions where actual sound sources would be (stage, podium, altar). The source should not be placed in corners or against walls unless that represents the actual use case, as boundary proximity strongly affects the low-frequency room response.

Receiver Microphone

The receiver should be an omnidirectional measurement microphone. Key specifications:

Frequency response: flat ±1 dB, 20 Hz – 20 kHz
Self-noise: below the room noise floor (typically < 20 dBA for precision measurement)
Dynamic range: sufficient to capture both the direct sound and the noise floor (typically >100 dB)
Height: 1.2 m for seated audience, 1.5 m for standing

Distance Considerations

For room characterization, the source-receiver distance should exceed approximately 3× the critical distance (where direct and reverberant field are equal). This ensures the measurement captures a representative sample of the reverberant field. For system alignment measurements, place the receiver at actual listener positions per ISO 3382-1 positioning rules.

Multi-Position Strategy

AES-2id recommends measuring at multiple positions and averaging to reduce spatial variance. The averaging section covers this in detail. When measuring for convolution reverb (auralization), capture multiple source-receiver combinations including binaural (dummy head) or ambisonic (B-format) receivers.

Avoiding Source-Receiver Coupling

Both source and receiver should be on vibration-isolated stands, not directly coupled to the floor or walls. Floor-borne vibration can bypass the acoustic path and contaminate the impulse response with structural transmission artifacts.

SonaVyx Setup

In single-device mode, the phone acts as both source and receiver — position it at the listener location. In multi-device mode, one device at the source position plays the sweep while another at the receiver captures. The IR measurement tool guides setup for both configurations. For SNR verification after capture, see the next section.