Influence of speech activity on vibrometer signals to extract vital parameters of humans

Authors: Kristian Kroschel, Jürgen Metzler

Abstract:

For the measurement of vital parameters of the heart the elekrocardiogram or ECG is used. If a non-contact measurement is required the vibrocardiogram or VCG is more appropriate. During the measurement normally the client isquiet because she or he is realizing that the measurement is going on. This is notthe case when the VCG is picked up because for comfort and to protect the eyesinfrared lasers are used.The VCG measures the speed of the surface of the skin invoked by the activity ofthe heart. Therefore clients are asked not to move since this would influence theresult of the mesurement. It can be shown that also speaking influences the VCGsignificantly despite the fact that airborne sounds like the human utterance covera different frequencey range than the heart activity. Obviously the structure-bornesounds emitted from the vocal chords influence the VCG.In this paper this phenomenon is investigated in detail and a method is derived withwhich the utterance of a human can be detected based on a figure of reliabilityextracted from the VCG.For the measurement of the heart beat frequency only those sections of the VCGare exploited in which the client does not speak.