Noise Killer Tests With Super Puma


Description of Test Procedure

A series of tests on the effectiveness of the Lectret Digital Noise Killer were conducted. The test setup is as follows:

1.Two persons were each given a Lectret HS100 headset. Person “A” had his headset connected first to a Noise Killer and then to a Motorola GP328 radio, whereas Person “B”’s headset was simply connected directly to his respective Motorola GP328 radio.

2. Both persons were at a distance of 1m away from the helicopter.

3. The helicopter’s engine was started, and the noise generated measured 114 decibels on the SPL meter. A reference recording of this noise was recorded on a Sony DAT recorder.

4. Both persons took turns to speak through their radios, and their speech received on the receiving Motorola GP328 radio (situated at about 20m away) was recorded onto a second Sony DAT recorder.

5. These recordings were then transferred to a computer, which can be played back for evaluation in the following slides.

6. The wave files were also graphically captured for further detailed analysis.

7. All test results were then recorded and documented in this presentation material.


To further substantiate our test results and to help you make a better evaluation, the recordings were converted* to visuals that allow both Spectral and Wave Form Analysis.


Spectral View of Noise Killer Test Recordings


Speech (denoted by the red & yellow patches) with no surrounding noise


Speech with surrounding noise and with no Noise Killer


Speech with surrounding noise and with Noise Killer activated


Waveform View of Noise Killer Test Recordings


Speech with no surrounding noise


Speech with surrounding noise


Speech with surrounding noise and with Noise Killer activated

*MathLab was used in the generation of the spectral and wave forms views.


Test Observations

It was observed that:

The high noise levels generated from the helicopter’s engine is impeding communications by reducing speech intelligibility, and this will affect the effectiveness of the crew during operation.

The Digital Noise Killer was able to effectively eliminate the background (engine) noise and enhance speech intelligibility, which will in turn help in improving the communication channels between the crew members.


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