How does acoustic testing for cracks in eggs work?

What is acoustic crack testing?

It is an inspection method in which the shell receives a light tap and the sound it returns is listened to and interpreted. It is used to find hairline cracks, which are too fine to show under normal light (see hairline crack).

In general terms, the method observes the shell's resonance, that is, the way it vibrates after a tap. An intact shell responds one way; a cracked shell responds another. That is why the test can point to a crack that no eye or surface camera can see. More on this defect in hairline cracks in eggs.

Why does a crack change the egg's response?

Because a crack interrupts the continuity of the shell, and the vibration travelling through it changes. The shell behaves like a vibrating structure: when a fracture line is present, the energy of the tap is distributed differently, and the response stops matching that of an intact egg.

The method shows that the response has changed, but turning that difference into a decision requires comparison with intact eggs and calibration of the process. Without that calibration, the response alone does not tell whether the difference is a crack or normal variation in the shell.

What does acoustic testing detect, and what does it miss?

In practice, the method has a narrow reach: it is aimed at shell integrity, mainly hairline cracks.

• Detects: hairline cracks, through the change in the sound response.
• Misses: dirt and stains on the shell, which are handled by visual inspection.
• Misses: interior defects, such as the air cell, yolk and blood spots, which candling examines.

This list is a practical assessment of the method's reach, not a table from any standard. It shows why no single method covers every defect.

Where does acoustic testing fit in grading?

It fits as a complement. The camera handles dirt and visible cracks, candling examines the inside of the egg and the fine cracks, and acoustic testing targets the hairline cracks that the camera lets through.

The order and the combination depend on each establishment's process and on what the line needs to control. In either case, acoustic testing should not be seen as a substitute for the camera or for candling, but as a step that covers the part they do not reach.

What does Vigiovo do in this case?

Vigiovo does not perform acoustic testing. It is visual inspection software that uses a camera and grades eggs as clean, dirty, cracked or unverified.

So Vigiovo deals with visible cracks and dirt, and makes clear that hairline cracks call for candling or acoustic testing. By removing dirty eggs and visibly cracked eggs before those methods, it helps leave a cleaner batch for the next step. The comparison between the two kinds of inspection is in visual vs acoustic crack detection. Details are on how it works.

Frequently asked questions

Does acoustic testing replace the camera?

No. The camera handles dirt and visible cracks, and acoustic testing looks for hairline cracks, which a camera cannot see under normal light. Because the two cover different parts of the problem, combining them is usually more useful than either one alone.

Does acoustic testing detect dirt on the shell?

No. Dirt and stains are not the target of the method, which focuses on shell integrity. Those marks are handled by visual inspection, which measures the dirty area of the shell in the image.

Can an egg with a hairline crack pass the camera?

Yes, because hairline cracks do not show under normal light and no surface camera sees them reliably. That is why the line needs an additional method, such as candling or acoustic testing, for this kind of crack.

Sources

1. Como o Vigiovo classifica ovos sem IA / How Vigiovo grades eggs without AI, Vigiovo