ISO 3382-1 Microphone Positions: Source-Receiver Layout and Spatial Averaging
TL;DR
ISO 3382-1 Clause 7.3 specifies positioning requirements. Source positions should represent actual performer locations. Receiver positions should represent audience seating areas. Minimum source-receiver distance: at least 1 wavelength at the lowest frequency of interest (typically ≥3 m). Receiver height: 1.2 m (seated audience). Minimum measurement positions depend on required precision: 6 source-receiver combinations for "survey" accuracy, 12 or more for "engineering" or "precision" grades. Results are spatially averaged (arithmetic mean for T, energy-averaged for C, D, G).
Source Positioning (Clause 7.3)
Source positions must be representative of actual sound source locations in the space. For concert halls, this means positions on the stage. For lecture halls, the podium location. ISO 3382-1 recommends at least 2 source positions to capture spatial variation. The omnidirectional loudspeaker should be placed at a height of 1.5 m above the floor (approximate head height of a standing performer).
Receiver Positioning (Clause 7.4)
Receivers (microphones) must be placed in the audience area at seated ear height of 1.2 m. Key spacing rules:
- Minimum source-to-receiver distance: half the estimated critical distance, or at least the distance corresponding to one wavelength at the lowest frequency of interest
- Minimum receiver-to-receiver distance: half a wavelength at the lowest frequency (typically ≥2 m)
- Minimum distance from any reflecting surface: one quarter wavelength (typically ≥1 m)
Receivers should be distributed evenly across the seating area, including positions at different distances from the source and at different lateral offsets.
Number of Positions
The standard defines three measurement accuracy grades:
| Grade | Min source positions | Min receiver positions | Min combinations |
|---|---|---|---|
| Survey | 1 | 3-6 | 6 |
| Engineering | 2 | 6-10 | 12 |
| Precision | 2 | ≥10 | ≥20 |
More positions reduce measurement uncertainty by better sampling the spatial variation of acoustic parameters.
Spatial Averaging
Results from individual positions are combined by spatial averaging. The averaging method depends on the parameter:
- T20, T30, EDT: arithmetic mean across positions
- C50, C80, D50: energy-weighted average (convert to linear, average, convert back to dB)
- G (sound strength): energy-weighted average
- Ts: arithmetic mean
Standard deviation across positions is reported alongside the mean to indicate spatial uniformity.
Practical Considerations
In occupied spaces, receiver positions may be constrained by seating layout. Temporary installations (microphone stands in aisles) are acceptable. Background noise should be minimized during measurement — turn off HVAC if possible. The noise floor determines the achievable INR and hence whether T20 or T30 can be reliably extracted.
SonaVyx Multi-Point Workflow
The SonaVyx RT60 tool supports multi-position measurement via the session system. Take an impulse response at each position, and SonaVyx computes spatially averaged parameters across all captured positions. Each position's results are stored individually for inspection alongside the spatial average.
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Last updated: March 19, 2026