Which ISO Standard Should You Use for Measuring Sound Power Levels (PWL)?
06/12/2025
When measuring the sound power level (PWL) of acoustic devices or products, choosing the right ISO standard depends on your testing purpose, acoustic environment, and required accuracy.
This article explains the differences between ISO 3744, ISO 3745, and ISO 3746, along with guidance on selecting the appropriate one.
Overview of Each Standard
ISO 3744:2010 – Engineering Method
| Test environment | Semi-Anechoic Room |
| Sound field type | Free field over a reflecting plane |
| Permissible K2 correction | 0 ≤ K2 ≤ 4 dB |
| Key Features | ・Practical method for general product testing ・Relatively easy and cost-effective room construction ・Utilizes floor reflection as part of measurement |
| Use cases | Home appliances, IT devices, automotive components, and general industrial applications |
ISO 3745:2012 – Precision Method
| Test environment | Anechoic or Semi-Anechoic Room |
| Sound field type | Free field / Free field over a reflecting plane |
| Permissible K2 correction | K2 ≤ 0.5 dB (strict) |
| Key Features | ・High-precision sound power measurement ・Requires inverse square law compliance (typically with ≥ 0.99 absorption coefficient) ・Ideal for standardized measurements and certification |
| Use cases | R&D, certification, and high-accuracy product evaluations |
ISO 3746:2010 – Survey Method
| Test environment | Reverberant or untreated room |
| Sound field type | Allows for non-uniform fields |
| Permissible K2 correction | Larger; K2 correction often not used |
| Key Features | ・Focus on rough estimation rather than precision ・Strongly influenced by room reflections ・Suitable for quick checks or early-stage evaluations |
| Use cases | Preliminary noise assessments, product comparisons in development stages |
Which Standard Should You Choose?
Decision Flowchart:
Is high-precision official testing required?
- Yes → Choose ISO 3745
- No → Continue
Is there an acoustically treated room available (e.g., semi-anechoic)?
- Yes → Choose ISO 3744
- No → Choose ISO 3746
Summary Table
| Standard | Test Environment | Accuracy Level | K2 Allowance | Primary Use Cases |
|---|---|---|---|---|
| ISO 3745 | Anechoic / Semi-Anechoic | Precision Measurement | K2 ≤ 0.5 dB | High-accuracy testing, certifications, R&D |
| ISO 3744 | Semi-Anechoic | Engineering Measurement | 0 ≤ K2 ≤ 4 dB | General product evaluation, mid-stage development |
| ISO 3746 | Reverberant / Standard Rooms | Survey Measurement | Not specified | Rough estimation, initial product comparisons |
Sonora’s Technical Insight
Sonora offers ISO-compliant environments through the use of:
- MSAC (Modular Semi-Anechoic Chamber)
- MFAC (Modular Fully-Anechoic Chamber)
These chambers are equipped with BFW (Broadband Fractal Wedge) absorbers, which provide exceptional wide-band absorption from low to high frequencies. This ensures easier compliance with the inverse square law and enhances measurement reliability across ISO 3744 and ISO 3745 applications.