Portable Acoustic Measurement Device for Random Sound Fields
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Solution Overview
Problem
Existing methods for determining acoustic absorption and transmission coefficients, as well as acoustic power emitted by a source, are cumbersome, costly, and limited to specific sound fields, making them impractical for random sound fields and difficult to implement outside laboratory settings.
Innovation Solution
A method and device that measure sound pressure and particle velocity, calculate Fourier transforms, and determine time-averaged active and total intensities to derive absorption and transmission coefficients, and emitted power, using a portable apparatus capable of operating in random sound fields without requiring specific sound sources or environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to determine acoustic absorption and transmission coefficients, then measurement accuracy is maintained for specific sound fields, but the measurement process becomes cumbersome, costly, and limited to laboratory settings
Solution Approach 1:
The patent replaces complex mechanical measurement setups with a portable device that uses electronic signal processing. Instead of requiring elaborate acoustic environments and multiple sensors, the invention uses a single portable device that measures sound pressure and particle velocity, then calculates acoustic coefficients through Fourier transforms and intensity calculations, thereby substituting mechanical complexity with electronic computation
Solution Approach 2:
The patent transforms the measurement approach by changing from direct measurement of acoustic coefficients to measurement of intermediate parameters (sound pressure and particle velocity) that are then mathematically transformed. By measuring p(t) and v(t) and computing their Fourier transforms P(f) and V(f), the system derives intensity values Iac(f) and Itot(f), which are then used to calculate absorption and transmission coefficients, thereby simplifying the physical measurement setup
2Ease of operation
If conventional methods are used to determine acoustic power in echoing spaces, then measurement simplicity is maintained in non-echoing spaces, but measurement accuracy deteriorates due to acoustic reflections
Solution Approach 1:
The patent converts the harmful effect of acoustic reflections into a beneficial measurement capability. By measuring both sound pressure and particle velocity, the system can distinguish between direct sound and reflected sound through their different phase relationships. The particle velocity measurement provides directional information that allows the system to calculate incident intensity separately from reflected intensity, thereby enabling accurate acoustic power measurement in echoing spaces that would otherwise corrupt the measurement
3Reliability
If conventional methods are used for acoustic measurements, then results are reliable for known sound fields, but adaptability to random sound fields and practical conditions is lost
Solution Approach 1:
The patent creates a universal measurement device that can handle multiple sound field types (plane waves, spherical waves, diffuse fields, and random sound fields) using the same measurement principle. The portable device measures sound pressure and particle velocity regardless of the sound field type, then uses Fourier transforms and intensity calculations to derive acoustic coefficients applicable to any sound field condition, thereby achieving multi-functionality and broad adaptability
4Productivity
If rapid and simple measurement is implemented, then productivity and ease of operation improve, but measurement precision and reliability may deteriorate
Solution Approach 1:
The patent replaces time-consuming manual measurement procedures with automated electronic signal processing. The portable device continuously measures sound pressure and particle velocity, performs real-time Fourier transforms, and automatically calculates acoustic coefficients through programmed intensity computations, thereby achieving both rapid measurement and high precision through electronic automation rather than manual procedures
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid, reliable, and cost-effective measurements of acoustic coefficients and power in practical conditions, applicable to random sound fields, and allows for in situ determination of emitted power by integrating incident intensity over an enveloping surface.
Implementation Method 1
measuring the sound pressure p(t) and the particle velocity v(t) at a chosen position in the space
Implementation Method 2
measuring the sound pressure p(t) and the particle velocity v(t) at a chosen position in the space
Implementation Method 3
calculating the Fourier transforms P(f), V(f) of p(t), v(t) ; calculating on the basis of P(f) and V(f) the time-averaged active intensity Iac(f)
Implementation Method 4
determining the emitted acoustic power Pin(f) by integrating Iin(f) over the enveloping surface
Data Source
Figure 1
AI summary
A method for determining the acoustic absorption coefficient and/or the transmission coefficient at a chosen position in a space in which a certain sound field prevails as a result of the operation of a sound-emitting source.