Why Sound Intensity?
Sound intensity measurements provide unique advantages compared to traditional pressure measurements, especially for sound power determination in actual operating environments.
No Special Acoustic Rooms Required
Measure sound power in the actual operating environment without expensive anechoic or reverberant chambers.
Work in Background Noise
Intensity technique separates incoming and outgoing energy, allowing measurement even with other noise sources nearby.
Determine Energy Flow Direction
Unlike pressure measurements, intensity is a vector quantity that identifies the direction of sound energy flow.
Identify Dominant Sources
Create intensity maps to determine which parts of machinery contribute most to overall noise.
Measure Large Machinery
Ideal for large industrial equipment that cannot be transported to an acoustic laboratory.
International Standards
Sound intensity measurements are governed by the ISO 9614 series for sound power determination, with additional standards for instrument specifications.
ISO 9614-1
Discrete Points Method
Sound power determination using sound intensity at discrete measurement points on a measurement surface. Suitable for complex noise sources.
ISO 9614-2
Scanning Method
Sound power determination by continuously moving the intensity probe over the measurement surface. Faster than discrete points.
ISO 9614-3
Precision Method
Scanning method with stricter requirements for highest accuracy in sound power determination.
ISO 3741
Sound Power - Reverberant Room
Sound power level determination in reverberation rooms. Reference for comparison with intensity methods.
ISO 3744
Sound Power - Field
Sound power level determination under free-field conditions. Can be supplemented with intensity measurements.
IEC 61043
Intensity Instruments
Requirements and specifications for sound intensity measuring instruments per international standards.
Key Parameters
Understanding intensity measurement parameters and quality indicators is essential for obtaining accurate and reliable results.
LI
Sound Intensity Level
Sound intensity level in decibels referenced to 1 pW/m². Can be negative when energy flows in the opposite direction.
LW
Sound Power Level
Total acoustic power emitted by the source. Calculated by integrating intensity over the measurement surface.
p-I Index
Pressure-Intensity Index
Difference between sound pressure level and intensity level. Indicator of measurement field quality and reactive field effects.
F-pI
Field Pressure-Intensity Index
Measure of acoustic field reactivity. High values indicate strong reactive field requiring additional care.
δpI0
Dynamic Capability Index
Maximum allowable difference between pressure and intensity to ensure measurement accuracy.
Spacer
Spacer Distance
Distance between the two microphones in the probe. Determines measurable frequency range (12mm: 250-10kHz, 50mm: 50-5kHz).
Applications
Sound intensity measurements have broad applications in industry, product development, and quality assurance.
In-Situ Sound Power Determination
Measure machinery sound power directly in the operating environment without special acoustic rooms. Ideal for large equipment that cannot be moved.
Noise Source Identification
Locate and rank contributing noise sources on complex machinery. Create intensity maps to visualize sound energy distribution.
Transmission Path Analysis
Trace sound energy flow through panels, enclosures, and structures. Identify weak points in noise control design.
Noise Reduction Verification
Measure sound power improvement before and after applying noise control treatments to quantify effectiveness.
Product Development
Characterize noise properties during R&D phase to design quieter products and improve sound quality.
Quality Assurance
Production line testing to verify product compliance with specified noise specifications.
Required Equipment
Sound intensity measurements require specialized equipment. All the following components are essential for a complete measurement system.
Required for sound intensity measurements because the probe uses two phase-matched microphones.
Two phase-matched microphones with precision spacers to measure pressure gradient.
Automated calculations for sound power, quality indicators, and report generation.
Measurement Procedures
Follow these step-by-step procedures to perform sound intensity measurements correctly according to ISO 9614.
- 1Define measurement surface enclosing the source (usually a rectangular parallelepiped)
- 2Divide the surface into equal-area sub-segments
- 3Calibrate the probe using pressure and intensity calibrator
- 4Measure intensity at the center of each sub-segment perpendicular to surface
- 5Record p-I index at each point to verify measurement quality
- 6Calculate sound power LW = 10 log(Σ Ii × Si)
- 1Define measurement surface and sub-segments
- 2Calibrate the probe (pressure and intensity)
- 3Move the probe slowly and uniformly over each sub-segment
- 4Keep the probe perpendicular to the surface throughout the scan
- 5Check quality indicators (F-pI, δpI0)
- 6Repeat measurement if quality indicators don't meet requirements
- 112mm spacer: For high frequencies (250 Hz - 10 kHz)
- 250mm spacer: For low frequencies (50 Hz - 5 kHz)
- 3For full range: Perform two measurements with both spacers
- 4Combine results: Use 50mm for frequencies < 500 Hz and 12mm for > 500 Hz
- 5Check overlap in the 250-500 Hz region
- 6Use Nor850-SI software for automatic combination
Frequently Asked Questions
Sound Intensity Applications in GCC Industry
Sound intensity measurements are widely used across key industrial sectors in the GCC to ensure compliance with international standards and protect workers and the environment.
Oil & Gas
Sound power testing of pumps, compressors, and turbines at oil and gas refineries. ISO 9614 compliance for equipment acceptance testing in petrochemical facilities.
Desalination Plants
Noise source identification on RO pumps and thermal systems. Equipment noise control verification at SWCC and DEWA plants.
Power Generation
Generator and turbine sound power per ISO 9614. Gas turbine exhaust noise mapping.
Manufacturing & Assembly
Production line noise source identification for worker safety. Machine noise acceptance testing per purchase specifications.
HVAC & MEP Systems
AHU, chiller, and cooling tower sound power testing. Equipment noise verification for building acoustic compliance.
Automotive & Transport
Vehicle noise source identification. EV motor noise characterization. Railway noise mapping.
Transformer Sound Intensity Measurements to IEC 60076-10
IEC 60076-10 defines the sound levels of power transformers and reactors, including the sound intensity method. IEC 60076-10-1 provides the application guidance for carrying out the measurement. Our systems support on-site determination of sound power for power transformers at substations, with full tonal analysis of the characteristic 100/120 Hz hum and its harmonics.
Why sound intensity for transformers?
Measure on-site, no special test environment
The sound intensity method determines the transformer's sound power level directly at the substation, in the presence of background noise and reflecting surfaces — no reverberation room or anechoic chamber required.
Built for the transformer's tonal hum
Transformers radiate a tonal hum at twice the mains frequency (100/120 Hz) and its harmonics. Sound intensity delivers precise third-octave and narrowband spectral analysis of these tonal components.
Rejects steady background noise
Unlike the sound pressure method, the intensity method rejects steady contributions from background noise, enabling reliable measurements at busy industrial and utility sites.
Locate the loudest surfaces
Scanning the measurement surface reveals the highest-radiating areas — tank walls, radiators and cooling fans — to target noise-control measures on an ALARA basis.
IEC 61043 Class 1 instrument
The Nor150 sound & vibration analyser paired with the Nor1290 sound intensity probe forms an IEC 61043 Class 1 measurement system — the instrument required for the sound intensity method in IEC 60076-10, with full support for ISO 9614-1/-2/-3 sound power determination.
What you receive
- A-weighted sound power level (LWA) over the defined measurement surface
- Third-octave and narrowband spectra resolving the tonal components
- Sound intensity maps identifying the highest-radiating areas
- Traceable compliance report against purchase-spec limits or IEC 60076-10
Why Choose Sound Intensity Over Sound Pressure?
A comprehensive comparison between sound intensity measurements and traditional sound pressure measurements showing the clear advantages of the intensity technique.
| Criteria | Sound Intensity | Sound Pressure |
|---|---|---|
| Environment Required | No special acoustic rooms needed | Expensive anechoic chambers |
| Background Noise | Works in background noise | Requires quiet environment |
| Directional Information | Full directional information | No directional data |
| Measurement Location | In-situ measurements | Laboratory only |
| Source Ranking | Source ranking capability | Overall level only |
