Lie detector was once used in police investigations. There were considered very accurate and worked on your bodily responses. It was known that when a person lies his bodily responses changes and these changes were detected by the lie detector tests. The machine-like any other polygraph only prints the changes in graphical form and alters the investigator when the graph changes and this is assumed to be the point that the person is lying. However, this is based on the interpretation by the examiner.
Voice stress analysis
One of the components of the lie detector tests is the voice stress analysis. There are different components to your voice when we even speak normally. Your voice comprises of frequency, pitch, intensity, and microtremors. Depending on our mood and situation, there are changes in these components. For example, if the person is angry at the frequency and the pitch would change intending that the person is aggravated. If the person is embarrassed or shy for some reason, there would be a change in the voice and the various components of the voice. The same applies when the person is lying, the stress in the voice and the various components changes.
How Does It Work?
When a person is lying, the vocal chords tend to produce a distorted sound wave, due to the involuntary interference. The sound wave so produced is definitely different from the sound wave produced when the person is telling the truth. The voice of the person telling the truth could have been pre-recorded and then compared to when the person was asked the questions that he is suspected of lying. If there is a difference in both the sound waves than it can be assumed that the person is lying. However, it is not % sure that the person is lying since this is very subjective and based on the bias of the examiner or the person comparing the sound waves for changes.
The Tests are Based on the Examiner
Again lie detector tests are very subjective and completely based on the examiner. This kind of tests sometimes used in banks and other financial institutions in case of fraud or misconduct by one of the employees. Since these are not people used to lying on a daily basis and the sudden questions could cause minor changes due to the sudden stress of answering the question and lying, in case there has been a fraud or a misconduct carried. However, this was one of the primitive methods of detecting a lie and no longer in use, since it’s not % accurate and the changes in the voice stress level could be due to other factors also.