Voice Stress Analysis

Current trends indicate that people and organisations are actually moving away from the traditional Polygraph test (the one made famous by movies), to the new Voice Stress Analysis (VSA). Opinions do differ in terms of which method is better, but the industry is certainly moving in the direction of the VSA.

How does a VSA work?

In short, the VSA measures the flexibility of a subject’s vocal chords. Typically, when a person is put under stress, they will enter into “fight, flight, or freeze??? mode. This in turn causes their throat muscles to tighten, which has an effect on their vocal chords. Subjects are asked a range of questions by a qualified analyst, and the VSA measures the physical changes taking place in the subject’s body. However, unlike a polygraph, this is not done through any physical attachments.

The VSA is a much friendlier test in terms of how it interacts with the subject. Figures suggest that typically around 80% of people that are tested are actually ‘innocent’, and so it certainly makes sense to give these subjects a much friendlier test.

Polygraph vs VSA

Chris Nel, the Managing Director of Welcor Truth Verification Center, suggests that people should do their own research into both the polygraph and the VSA.


In short the benefits of the Voice Stress Analysis include being:

  • More hygienic;
  • More subject friendly; and
  • Less intimidating to subjects.


However, in many cases it is a personal decision as to which method is better. Some of the key differences between these two methods, which mostly point towards the benefits of VSA, include:

  • The VSA doesn’t make use of any physical attachments;
  • Subjects are free to move around as they wish;
  • VSA is a much newer technology than the polygraph;
  • The only possible countermeasure is for subject to be ‘silent’;
  • All results are claimed to be conclusive;
  • Alcohol, drugs, age and health will not impact on results;
  • An unlimited number of questions can be asked in the test; and
  • Result charts are able to show and quantify stress patterns.


 Dismissing an employee based on a VSA

Remember that an employee cannot be dismissed purely as a result of a Polygraph or Voice Stress Test. The results of these tests can and must only be used as supporting evidence when a case is presented at the CCMA.

If you are attempting to dismiss an employee based on that person failing a Voice Stress Test, you must make sure that the following is in place:

  • Correct paperwork, including a release form signed by the subject;
  • Once the test has been conducted, charts have been analysed (in front of subject), and the subject has shown deception to some or other degree, you should tell the subject that they  have failed, and then complete the report and forward this to the client; and
  • The client needs to hold a disciplinary hearing.


Subsequent to this, normal procedures would need to be followed, as per the relevant labour laws, if you wish to dismiss the employee. For advice on this, as well as help in any regard, iFacts is able to provide information and further details.

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