Influence of speach activity on vibrometer signals to extract vital parameters of humans
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 is quiet because she or he is realizing that the measurement is going on. This is not the case when the VCG is picked up because for comfort and to protect the eyes infrared lasers are used. The VCG measures the speed of the surface of the skin invoked by the activity of the heart. Therefore clients are asked not to move since this would influence the result of the mesurement. It can be shown that also speaking influences the VCG significantly despite the fact that airborne sounds like the human utterance cover a different frequencey range than the heart activity. Obviously the structure-borne sounds emitted from the vocal chords influence the VCG. In this paper this phenomenon is investigated in detail and a method is derived with which the utterance of a human can be detected based on a figure of reliability extracted from the VCG. For the measurement of the heart beat frequency only those sections of the VCG are exploited in which the client does not speak.