Impulse Response Measurement per IEC 61672-1

TL;DR

IEC 61672-1 defines the electroacoustic performance of sound level meters used in measurement chains for impulse response capture. When using the interrupted noise method, the meter must comply with IEC 61672-1 for the decay recording. When using the integrated impulse response method, the standard defines the performance of the analog front-end (microphone through preamp through ADC) that captures the raw signal. SonaVyx implements IEC 61672-1 compliant digital processing and leverages the full 24-bit resolution of modern audio interfaces to maximize the dynamic range available for impulse response measurement.

IEC 61672-1 for IR Measurement

While IEC 61672-1 is a sound level meter standard, its specifications for frequency response, dynamic range, and linearity directly apply to the measurement hardware used for impulse response capture.

Instrument Classification

Class 1 instruments are recommended for IR measurement in performance spaces per ISO 3382-1
Class 2 instruments are acceptable for IR measurement in ordinary rooms per ISO 3382-2
The classification affects allowable measurement uncertainty in the final results
Digital implementations can achieve performance between Class 1 and Class 2 depending on the analog front-end

Frequency Response Requirements

The measurement system must have flat response (within class tolerance) across the frequency range of interest
For room acoustic measurements, this is typically 63 Hz to 8 kHz
IEC 61672-1 Z-weighting tolerances apply to the capture chain
Microphone calibration files can correct for known deviations

Dynamic Range and Linearity

IEC 61672-1 specifies the linear operating range of the meter. For impulse response measurement, you need the maximum linear range to capture both the peak of the excitation and the decay to the noise floor. The linearity range determines whether your IR is distortion-free.

Practical Implications

When measuring impulse responses with a browser-based tool like SonaVyx, the IEC 61672-1 compliance depends on the combination of the external microphone, audio interface, and the digital processing. The digital processing meets or exceeds the standard; the limiting factor is typically the analog components.

Common Mistakes

Not matching the instrument class to the measurement standard requirements
Overdriving the input, causing clipping that corrupts the impulse response
Setting gain too low, reducing the usable dynamic range
Not calibrating the microphone frequency response

SonaVyx Implementation

The SonaVyx IR tool uses IEC 61672-1 compliant digital processing at 48 kHz sample rate. Import microphone calibration files for the SPL meter to correct frequency response. Extract RT60 with the RT60 tool. Verify system linearity with the transfer function. Check the RTA for spectral overview. Visit learning modules for detailed setup procedures.

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