Stealth – Acoustic Discretion – Radiated Noise Reduction

Context & Issue

Thalès developed infra-red binoculars. The on-board cold machine generated vibrations, reducing the infantryman’s stealth.

It was in this context that the DGA called on Vibratec to better understand and measure the phenomenon, and to study possible solutions.




Reducing the acoustic radiation from binoculars can help users to be more discreet in situations where they do not want to be detected.


Image quality

By reducing acoustic radiation, binoculars can produce clearer, sharper images.


User comfort

Acoustic radiation reduction enhances user comfort by reducing the noise emitted by the binoculars

Key Development Points


Modeling is an important step in the engineering process, as it creates a mathematical or physical model of a system, component or process. Modeling makes it possible to understand a system’s behavior and predict its operation, using equations, graphs, diagrams and other representation tools.


Load measurement

Loads can be forces, moments or torques, and can be measured using various types of sensors or measuring devices.


Addition of suspension studs

The addition of suspension studs can have several advantages in technical systems.

  • Vibration reduction : Suspension blocks can be used to reduce vibration in structures and machines. They can absorb some of the kinetic energy generated by vibrations, thus reducing the forces transmitted to the structure and lowering noise and vibration.
  • Improved stability: Suspension blocks can improve system stability by reducing the impact of external forces. They can also improve systems’ ability to support heavy loads, by distributing forces more evenly.
  • Improved quality: Suspension blocks can improve product quality by reducing vibration and shock, thereby reducing manufacturing defects and improving product precision and quality.

Measuring acoustic gain

To measure the acoustic gain, it is necessary to take sound level measurements before and after the installation of the noise reduction or sound insulation system. Measurements can be taken using a sound level meter or a spectrum analyzer.

Once sound level measurements have been taken before and after installation of the noise reduction or sound insulation system, the sound gain can be calculated by subtracting the post-installation sound level from the pre-installation sound level.

Results and Benefits

Need to reduce the forces transmitted to the hull of the binoculars

The addition of suspension studs may be a solution for reducing the forces transmitted to the binocular hull by absorbing some of the kinetic energy generated by vibrations. Modeling results can help determine the optimal number and location of suspension studs to minimize the forces transmitted to the binoculars’ hull.


Development of an optimized decoupling system

Optimized decoupling involves taking into account a number of factors, such as the mechanical characteristics of the materials, the location of the suspension studs, the number of studs required, as well as the design parameters of the binoculars, in order to design an effective suspension system that minimizes vibration transfer and the forces transmitted to the binocular hull.


7 to 9 dBA gain in far-field conditions

A gain of 7 to 9 dBA in far-field conditions means that there was a significant reduction in the noise level perceived at a certain distance from the binoculars. A gain of 7 to 9 dBA is equivalent to a reduction in noise level of around 50%, which can be considerably perceptible to the user.

It’s important to note that the dBA gain is not linear with the reduction in actual sound power. Consequently, a 50% reduction in sound power does not necessarily correspond to a halving of the sound level perceived by the user. However, a gain of 7 to 9 dBA is considered significant and can considerably improve the user experience by reducing perceived noise levels.