In modern manufacturing, non-destructive testing (NDT) is a critical process for ensuring product integrity without compromising the material or part. The more prevalent testing method is Ultrasonic Testing, but lesser-known Acoustic Resonance Testing (ART) offers its own unique advantages.
While both techniques provide accurate defect detection, they differ in approach, application, and efficiency. This article compares UT and ART, highlighting how AI-driven acoustic resonant testing offers unique benefits for automated, high-volume production lines.
What is Ultrasonic Testing (UT)?
Ultrasonic testing (UT) is a well-established NDT method that employs high-frequency sound waves, typically ranging from 0.5 to 25 MHz, which are above the audible range for humans. In this process, a transducer generates sound waves that propagate through the material. When these waves encounter internal features such as flaws like cracks,voids, or boundaries, a portion of the wave energy reflects back to the transducer, creating an "echo."
The time-of-flight (TOF), amplitude and echo pattern of the reflected wave is used to determine the location, nature , size and geometry of the defect. The amplitude of the returned signal provides additional information about the flaw’s characteristics, such as depth and shape. This method is complex as the returned signal need to be analysed but it can be precise and can detect sub-surface defects in metals, composites, and other solid materials. This method is used to inspect the weld quality, thickness measurement, and integrity of bonds in adhesive joints.
Advantages of Ultrasonic Testing:
A non-destructive testing method
Versatile testing method – can be used across a wide range of materials, including metals, plastics, and ceramics
Provides deep penetration of a material and is able to detect very fine flaws
Suitable for small volumes
Can detect exact location and size of a defect
Suitable for large parts such as airplane wings and ships
Limitations:
Requires highly skilled operators for the interpretation of data
Surface conditions, such as roughness or complex geometries, are not compatible with UT
Slow scanning speed- Large areas require significant time to inspect point-by-point
Coarse-grained metals and composites can limit penetration depth cause poor signal quality makes flaw detection difficult
Equipment costs - Automated UT systems require significant investment in equipment and infrastructure
Dead zones - transducers can have a dead zone near the surface makes it difficult to detect defects that are located very close to the surface
What is Acoustic Resonance Testing (ART)?
Acoustic Resonance Testing (ART) is an advanced NDT technique that exploits the natural resonance frequencies of a component to assess its structural integrity. Every solid object has a set of unique resonance frequencies that are determined by its material properties, geometry, and internal composition. ART involves exciting the component—typically by mechanical impact, vibration, or air-coupled transducers—and measuring its vibrational response. Furthermore, ART operates effectively with complex geometrical shapes thanks to the wider dispersion of lower frequencies.
The vibrational spectrum of the test object is then compared to a reference spectrum of a “known good” part. Deviations in resonance patterns, such as shifts in frequency or amplitude, indicate potential defects. These can include cracks, inclusions, porosity, voids, and even subtle material inconsistencies such as variations in density, stiffness, or composition.
Advantages of Acoustic Resonance Testing:
Suitable for a larger variety of defects
Detects changes in material characteristics such as stress or hardness
Works well with complex geometries and surfaces
Limitations
Requires a skilled operator to analyse the frequency patterns
Requires “known good” reference parts for comparison
Does not indicate the exact location of defect
RESONIKS’ AI-Powered Acousting Resonance Testing - How Does it Work?
RESONIKS takes the ART method a step further by integrating machine learning algorithms into the testing workflow. Our system indexes the resonant signatures of defect-free parts during the training phase. The AI model analyses these data points and creates a highly sensitive profile that can detect even minute anomalies in newly produced parts. This results in a fully automated, objective, and repeatable testing process with minimal human intervention. With RESONIKS AI-powered defect detection, all the previous advantages of ART still apply, but with added benefits due to machine learning.
Advantages of RESONIKS AI-Powered ART:
Ideal for large production volume
High-testing speed increases throughput
Fully automated – no skilled operator needed
Fast and objective testing with no previous know-how necessary
Detect defects earlier in production process
Suitable for noisy production environments
Limitations:
Each part requires a training phase to familiarize our AI with your production
Does not indicate the exact location of defect
