How Does NDT-RAM Work?

Understanding Resonant Inspection with NDT-RAM

To help explain the Resonant Acoustic Method (NDT-RAM), let’s consider how a person can determine between a good bell Good and a cracked bell Bad.








Bell  Sound

Ear   Yellow Bolt


Quantify   Result
The impact “rings” the bell and produces sound. Ears pick up the sound and transform it to an electrical signal. The brain processes the signal into tones or notes, also known as frequencies. A comparison is made to bells heard before to determine “pass” or “fail.”









Hammer  Sound

Microphone   Yellow Bolt

Digital Controller

Quantify   Software
An industrial impactor taps each part with a measured and repeatable force, producing sound. A microphone is used to transform the parts' response into electrical signals for analysis. The smart digital controller uses a Fast Fourier Transform (FFT) method to determine frequency characteristics. NDT-RAM software compares the results to criteria limits and accepts or rejects the part accordingly.


NDT-How-it-works-product-1Impact the Part

The part can either be impacted with a manual hammer or an industrial electric hammer. It is important to excite the part with a proper, repeatable force. This will improve the repeatability and reliability of the test.




Measure the Response

A microphone is used to provide accurate acoustic measurement of the component's resonant frequency and amplitude values. The NDT microphone provides a perfect fit of price, accuracy and dependability.


Process the Data and Quantify the Results

Changes in mass, stiffness and damping due to certain defects can cause...

  • resonant frequency peaks to shift in both frequency and amplitude.
  • resonant frequency peaks to shift frequency but maintain amplitude.
  • peak shifts with more pronounced splits in resonant frequency.
  • resonant frequency peak energy to disappear completely.

The family of NDT-RAM systems range from a portable manual system ideal for parts investigation and troubleshooting, to a semi-automated system for easy integration into your existing process, to a fully automated conveyor-based or drop test fixture system as a turn-key solution for 100% parts inspection.