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HALT - Highly Accelerated Lifetime Tests

Microphone HALT testing is about securing long-term stability and robustness of a given product. It is a principle GRAS for years has relied on to develop products for both industry and laboratory as well as production environments.

Microphone HALT tests accelerate the lifetime and simulate the handling and use that a microphone is exposed to outside the laboratory, in real life conditions and beyond. By stress testing the products to the limits where they break down, we are able to learn and develop the microphone design to give robust and stable solutions thus precise-measuring microphones.


HALT - The GRAS Quality Mark

GRAS is known for its world-class measurement microphones - and not without reason. To make sure that our microphones can perform under real life conditions – and beyond – GRAS has created the testing standard HALT.


HALT consists of four different types of stress tests:

  • Temperature stress test at constant and cyclic temperatures

  • Humidity stress test

  • Vibration stress test

  • Mechanical impulsive stress test

With GRAS microphones being put through HALT, you will be able to minimize the downtime in your production by having a reliable repeatability and, in the end, minimize the need for replacement.

You can learn more about HALT and your data safety from the Microphone HALT Report 2015

Temperature Stress Test

Whether during storage or operation, microphones may be subjected to extreme temperatures. In the former case, the temperature is typically constant while in the latter case the temperature may vary greatly. Based on differing coefficients of thermal expansion, extreme temperatures may cause microphones to structurally distort thus altering their frequency response. Deviations from room temperatures may equally influence the polarization of CCP microphones, changing their sensitivity.


Humidity Stress Test

Humidity varies greatly with geography as does it with the quality of HVAC systems. It may severely affect the internal damping of a microphone. Moreover, long-term exposure to humid weather may lead to corrosion. GRAS microphones are specified to withstand levels of relative humidity ranging from 0% to 95%, both during storage and operation. In this humidity stress test, the microphone sets are sequentially stored for 48 hours at 90% relative humidity at a temperature of 50 °C.


Vibration Stress Test

Microphones may be vibrated during both transportation and operation. Prolonged exposure to severe vibrations may unsettle the critical elements making up a measurement microphone, the important components being: the diaphragm, the back plate, the insulator, the outer casing and the output contact.


Mechanical Impulsive Stress Test

Impulse stresses may accidentally be imparted to a microphone set during transportation and handling, often as a consequence of the microphone set or its container being dropped. However, impulse stresses may similarly occur during operation, if mounted on vehicles that undergo significant accelerations. A mechanical impulse may affect the internal workings of a microphone in a similar manner to that of vibrations, though with the additional possibility of large dents to the structure.


The HALT Video

In the HALT video, we take you through the four different types of stress tests, which we conduct on the microphones and simulate the handling and use a microphone is exposed to in real life conditions – and beyond. See the HALT video here.