ISO 15186-3:2002

Overview

ISO 15186-3:2002 - Acoustics: Measurement of sound insulation in buildings and of building elements using sound intensity - Part 3: Laboratory measurements at low frequencies.
This part specifies a sound-intensity method to determine the sound reduction index (R) and the element-normalized level difference (DIn,e) of building elements in the low-frequency band. It is applicable from 50 Hz to 160 Hz, and is mainly intended for 50 Hz to 80 Hz. The method gives significantly better reproducibility in typical test facilities than ISO 140-3, ISO 140-10 and ISO 15186-1, and produces results closer to those between rooms with volumes > 300 m3.

Key topics and technical requirements

• Measurement focus: Sound intensity measurements on the receiving side and sound pressure measured close to the specimen on the source side. Results can be combined with ISO 140-3 and ISO 15186-1 to cover 50 Hz–5000 Hz.
• Frequency range: 50 Hz–160 Hz (recommended 50–80 Hz for elements with thick porous absorbers).
• Room configuration: Receiving room opposite surface must be highly absorbing, converting the room acoustically into a duct with several propagating cross-modes; other surfaces should not be absorbing in the tested band. Source and receiving rooms must meet ISO 140-1 dimensional and reverberation requirements.
• Instrumentation: Intensity instrumentation must measure one‑third‑octave band intensity levels (reference 10‑12 W/m2), comply with IEC 61043 (class 1). A 50 mm spacer is recommended for most probes.
• Calibration & verification: Warm-up, microphone pressure calibration with an IEC 60942 calibrator, residual-pressure intensity index test (δ) and optional intensity calibrator checks. Residual-pressure index δ must be at least F_pI0 > F_pI + 10 dB.
• Measurement surfaces and procedure: Define a measurement surface enclosing the specimen on the receiving side; use scanning or discrete sampling with an intensity probe. Annexes cover laboratory qualification and estimated precision.

Applications

• Laboratory evaluation of low-frequency sound insulation for walls, doors, windows and building element assemblies.
• Product development and performance validation where low-frequency transmission is critical (e.g., heavy or multi-layer constructions, elements with porous facings).
• Providing robust test data for combination with higher-frequency methods to produce a full-spectrum acoustic rating (50–5000 Hz).
• Research and comparison of low-frequency sound transmission where improved reproducibility is required.

Who uses this standard

• Accredited acoustic test laboratories and national test houses
• Building-acoustics consultants and engineers
• Manufacturers of building elements (partitions, windows, doors, facade systems)
• R&D teams and academic researchers in building acoustics
• Standards bodies and conformity assessment organizations

Related standards

• ISO 140-1 (lab facility requirements)
• ISO 140-3, ISO 140-10 (laboratory airborne sound insulation)
• ISO 15186-1 (sound-intensity laboratory method)
• IEC 61043 (sound intensity instruments), IEC 60942 (sound calibrators)

Keywords: ISO 15186-3:2002, sound intensity, low-frequency acoustics, sound reduction index, element-normalized level difference, laboratory measurements, acoustic testing.