Traditional sound pressure measurement can only answer 'how loud is it', while sound intensity measurement reveals the magnitude and direction of sound energy, achieving a key leap from scalar to vector. The portable sound intensity measuring instrument is the engineering crystallization of this leap, which condenses complex acoustic principles into handheld devices and becomes the "acoustic stethoscope" for on-site noise diagnosis.

1、 Core principle: Dual microphone method and sound intensity vector

The core of the portable sound intensity meter is based on the p-p probe method (dual microphone method):

Basic formula: I ≈ (p ₁+p ₂)/2 * (p ₁ - p ₂)/(ρ₀ Δ r), where the sound intensity is determined by the product of the average sound pressure and the finite difference approximation particle velocity.

Key technological breakthroughs:

Phase matching technology: The phase deviation between two measurement channels in a wide frequency band (usually up to 10kHz) should be less than 0.5 °, which is the lifeline to ensure low-frequency accuracy.

The art of balancing spacing Δ r: small spacing (6-12mm) expands the upper limit of high frequency, while large spacing (25-50mm) improves low frequency performance. Modern probes often adopt multi spacing combination designs.

Adaptive calibration algorithm: real-time compensation for the impact of temperature and humidity changes on the sound velocity ρ₀ c.

2、 The miniaturization revolution of hardware architecture

Modern portable sound intensity meters are a fusion of precision machinery, electronics, and algorithms

Probe subsystem:

Microphone pair: Use pre polarized condenser microphones of 1/4 inch or smaller to achieve a dynamic range of>140dB.

Mechanical design: precise fixed spacing structure, built-in temperature and humidity sensors, using wind resistant spherical or cylindrical mask design.

Signal processing chain:

Front end ASIC chip: integrated with low-noise amplifier, anti aliasing filter, and 24 bit Δ ∑ ADC.

Real time digital signal processor: performs FFT analysis, sound intensity calculation, and direction determination.

Space acoustic compensation: automatically corrects the scattering effect of the probe itself.

3、 Software Algorithm: From Data to Insights

Core algorithm stack:

Frequency domain sound intensity calculation: using the cross spectral density method I (f)=Im {G ₁₂ (f)}/(2 π f ρ₀ Δ r).

Sound source separation technology: Combining beamforming and deconvolution algorithms to locate the main sound source in a reverberation environment.

Real time audio-visual rendering: Visualize the sound intensity vector field as a color cloud map, supporting video overlay.

Intelligent diagnostic function:

Abnormal voiceprint library matching: Built in libraries of typical fault features such as bearings, gears, and aerodynamic noise.

Trend analysis and warning: intelligent baseline comparison and warning threshold setting based on historical data.

4、 Breakthrough in engineering application scenarios

1. Abnormal noise location and fault diagnosis:

In automotive NVH debugging, the interior noise source can be accurately located within 60 seconds with an accuracy of ± 5 °

Industrial site identification of pump valve leakage and early bearing damage, with sensitivity increased by 10-15 dB compared to sound pressure method.

2. On site measurement of sound power:

According to the ISO9614 standard, replacing the anechoic chamber with scanning measurement can save 80% of time and cost.

Especially suitable for noise assessment of large equipment and outdoor installations.

3. Acoustic material performance evaluation:

Quantify the insertion and transmission losses of soundproof enclosures and mufflers.

On site measurement of the sound insulation performance of building envelope structures.

4. Analysis of Environmental Noise Sources:

Distinguish between tire noise and power system noise contributions in traffic noise.

Traceability of factory noise and clarification of responsible parties.

5、 Technological challenges and cutting-edge developments

Current limitations:

The Law of Low Frequency Limitation: Due to phase mismatch and Δ r limitation, the effective lower limit is usually 50-100Hz.

Nonlinear distortion at high sound pressure levels.

Measurement interference in airflow environment.

Technological frontiers:

Optical sound intensity probe: using laser Doppler vibration measurement technology to eliminate the influence of air medium.

MEMS microphone array: a micro array with more than 32 channels to achieve three-dimensional sound intensity imaging.

AI enhanced analysis: Deep learning algorithms automatically identify sound source types and fault modes.

Cloud edge collaborative architecture: Terminal collection+cloud based big data analysis to build an acoustic knowledge graph.

Conclusion: From Measurement Tools to Diagnostic Systems

Portable sound intensity measuring instruments have evolved from simple measuring instruments to the core sensors of intelligent acoustic diagnostic systems. With the continuous evolution of hardware miniaturization, algorithm intelligence, and platform networking, it is driving the transformation of noise control from "passive noise reduction" to "active acoustic design", becoming a technological equipment for industrial intelligence and fine environmental management.

In the future, a portable diagnostic platform that integrates sound intensity measurement, acoustic imaging, and vibration analysis will further enhance the ability of engineering sites to solve complex acoustic problems, realizing the technological vision of "measurement as diagnosis, data as insight".