DE2204501A1 - Method and device for analyzing a physiological response - Google Patents

Description

Hamburg, 26 January 1972 _o 116 272 9406

Priority: 9 »February 1971, USA, PatoAnmoNr. 113 949

Applicant?

Dector Gounterintelligence
and Security, Inc

Springfield, Virgo, USA

Method and device for analyzing a physiological response

The invention relates to a method for perceiving and measuring psychological stress as well as a facility to carry out the procedure,

For a long time has always been observed again that between the psychological stress and changes in physiological states relationships exist _o This relationship is used, for example, in triggering programmed reflexes due to psychological incentives, a process particularly by Pavlov in its encryption

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looking to conditional reflexes has been evidenced. Essentially the same properties have some basis for the development of processes in such diverse ways Areas such as applied psychology, advertising and hypnosis formed this form of the psyoho-physiological Relationship is well known; however, it only relates indirectly to the present invention

The second general type or category of psycho-physio-logical relationship that is a more direct relationship to the present invention relates to the detection and association of physiological changes that occur when psychological changes take place. " This side of the problem is particular to the medical one and psychological research and diagnosis, as well as being important for verifying the truth.

If the physiological effects of a change in psychological state are large enough, it is it is possible that a skilled observer can make a subjective assessment without aids. Far more accurate However, assessments can be made with the help of facilities designed to be proportionate Perceiving and measuring small physiological changes, The physiological changes that occur in most cases to be taken into account, concern brain waves, heart activity, conductivity of the skin and breathability ο A An example of such a process is described in US Pat. No. 1,788,434.

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The measurement of these processes actually provides a far more precise evaluation of the physiological response compared to direct observation without aids; In doing so, however, various disadvantages are introduced. Most of the difficulties are caused by the artificiality of the Test situation that mainly arises from the fact that it So far it has been necessary that Mhler participate in the Person to be attached, also have so far related procedures generally made it necessary to work in a controlled environment, from what Restrictions on the normal activity of the examiner have arisen «From these requirements it can be assumed that they induce a psychological state in the test subject, which in some cases just as or even stronger than the psychological state that is to be assessed » However, this significantly reduces the value of the investigation

The invention therefore aims to provide a method for evaluating psychological stress, in which the characteristics of physiological changes are perceived and measured, and the usual limitations are brought to a minimum or eliminated to such an extent that in certain embodiments the person examined does not need to know that she is being examined

The invention also aims at the use of human

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lichen voice as a medium in which changes in the physiological state due to psychological stress are perceived _e

Another purpose of the invention is to provide a facility which can record a viewable record this provides properties of the human voice that allow the perception of physiological changes and from which the presence of psychological stress can therefore be determined.

The method according to the invention includes the steps of recording oral utterances by a test person on a medium accessible for visual observation and identifying the frequency components of the recorded utterances, which reflect the physiological embodiment of the psychological stress identifiable are changes in the utterances of a test person, some of which are below the audible sound limit, whereby the changes below the audible sound limit are used as an indication of exposure »

The device according to the invention has a converter device to convert the oral utterances of a test person into electrical signals, means for conversion of the ^ frequency modulations in these electrical signals in amplitude modulations, which are then recorded

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so that a viewable record is created which can be checked for indications of psychological stress for examination ₀

With the invention, psychological stresses are perceived by the fact that the occurrence is physiological Changes in human voice will be assessed For this purpose, the utterances of a test person are converted into electrical signals and then processed further, to highlight selected properties that have been determined to accommodate the changes of the psyoho-physiological state change · The further processed signals are then displayed, for example on a continuous recording film, and can be accounted for, compared and analyzed · As A modulation of the voice in the infrasound range has proven to be particularly useful for this purpose highlighted "A device for carrying out this process comprises a transducer, a magnetic 'a a series diode, a plurality of integrating capacitors, an amplifier and a film recording device on · a second device contains filters, a frequency modulation discriminator and a detector, a waveform integrator, an amplifier and an attenuation device Creation of an authorized recording "

Further advantages and features of the invention result

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from the claims as well as from the following description and the drawings, in which exemplary embodiments of the invention are explained and shown o It show

Pig. I and 2

Mg. 3a - 3o

Mg, 4a - ο

KLg- 5
FIg, 6

records produced according to the invention to illustrate the features of the invention stocks,

a record used in a test of the method according to the invention has been produced according to the invention, parts of a record that is in a Testing of the method according to the invention with a device according to the invention has been made

a blook diagram of a ι according to the invention
Establishment and

a circuit diagram of a further according to the invention Device »

The so-called voice vibrato is considered half voluntary Reflex has been recognized to be of value in examining delusions along with certain other reactions can be, such as the tidal volume, the ratio of inhalation to exhalation, the metabolism the regularity and extent of perspiration, the association of words and thoughts, the expression of spirit, of motor reactions and reactions to

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Certain narcotics _o For this purpose reference is made to the article by Paul V ₀ Trovillo p "A History of Lie Detection", in "The Joarnal of Criminal Law and Criminology", March / April, May / June 1959 ο So far, however, no useful method has been developed, that allowed a valid and reliable analysis of voice changes in the clinical determination of mood, opinions, or attempted deception of a subject

Because of earlier attempts, which were aimed, among other things, at correlating the changes in voice quality with emotional stimuli, GoB ₀ Seashore, "Phonophotography in the Measurement of the Expression of Emotion in Music and Speech", Sol «Mon, 24 : 463-471 (1927) and Milton Metfessel, "What is the Voice Vibrato?" Referred to in Psychol. Monoge 39 (2), 126-134 (1928), these authors have found that human language is influenced by strong emotions', but so far it has not been established that these changes are directly related to the functioning of the autonomic nervous system "In fact, the results of recent experiments have shown that noticeable changes in the voice occur much more frequently as a result of stress stimuli than the classic displays of physiological expressions caused by the activation of the autonomic nervous system _{or the like}

These experiments have further shown that two types of voices

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Changes due to pressures are present «The first type of these changes can be referred to as gross change which usually only occurs due to a particularly stressful situation. This change expresses itself in noticeably noticeable changes in the extent of speech, in volume, trembling of the voice, changes in the spacing between syllables and a change in the basic key or frequency of the voice ο This gross change is consciously monitored and controlled at least in some subjects when the exposure level is below that at which a complete loss of control occurs.

The second type of change in voice observed was that of voice quality ο This type of change can be dated from human ear cannot be perceived, and is apparently an unconscious expression of the insignificant Tension of the vocal cords even with low loads, resulting in a dampening of selected frequency variations results ο The difference is in graphical reproduction easily recognizable, the one between the normal or unstressed vocalization and the vocalization under weak Stress, attempts to deceive or a contrary attitude occurs »These observation patterns are within a wide range of human voices of both sexes, of various age groups and confirmed under the most varied of situational conditions. This second kind of change is not subject to conscious control

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The human voice machine produces two types of sound, or loud,. The first type of sound is produced by the vibration of the vocal cords, which in turn is caused by partially closing the glottis and forcing air through the glottis by contracting the chest and lungs. The frequency of these vibrations can generally vary between 300 Hz, depending on the gender and age of the speaker and on the intonations used by the speaker. " This Sohall has a short expiry time ₀

The second type of sound or swoop contains the formant frequencies <> This reverberation results from the resonance of the cavities in the head, including the Raohens, the oral cavity, the bevel and the maxillary sinuses «This sound is produced by the resonance cavities be excited with a sound source of low frequency, in the case of the voiced sound through the vocal cords or duroh the partial restriction of the duroh-

ganges of air from the lungs in the case of voiceless fricatives · Which also may be the source of excitation, the The frequency of the formant is determined by the resonance frequency of the cavity involved · The formant frequencies generally occur around 800 Hz in different from each other Frequency bands which correspond to the resonance frequencies of the individual cavities. The first or the lowest formant is that which passes through the mouth and pharynx is created «She is particularly daring

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Attention should be paid to the frequency shift, as the pharynx changes its dimensions and its cavity as the various sounds are formed, especially when the voices are vocal. The highest formant frequencies have a higher frequency because the volume of the associated cavities has a greater constancy. The formant waveforms are sounding signals, in contrast to the rapidly falling signals of the vocal cords. ₀ When speech sounds are uttered, the speech waveforms are superimposed on the formant waveforms as amplitude modulations

It has been found that there is a third type of signal in the human voice, that of the one discussed above The second type of voice change is related to «This is an infrasound frequency modulation that is called one which lies below the audible sound limit, which to a certain extent both in the sounds of the vocal cords as well as in the formant sounds. This The signal is typically between 8 and 12 Hz · Accordingly, it is not audible to the human ear · Due to the The fact that this property, unlike amplitude modulation, is frequency modulation, it is not immediately recognizable from recordings "which give a time-related amplitude representation", Da this infrasound signal is one of the most characteristic indicators of a voice for psychological Loads, it will be dealt with in detail later «

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There are several analogies that are used to provide schematic representations of the entire vocal process. For example, both mechanical and electronic analog devices are successfully used in the production of computer voices. These analogies, however, consider the voiced sound source, i.e. the vocal cords and the walls of the cavities as hard and as a constant characteristics of _o However, both the vocal cords and the walls of the main lOrmanten forming cavities are actually pliable fabric which is responsive directly to the complex array of muscles which made lichene a control of this fabric These muscles, which dominate the vocal cords through the mechanical connections of bones and tendons, allow both intentional and automatic generation of voices and changes in the pitch of a person Mastering brooks, both the purposeful and the automatic mastery of the first formant frequencies. "Other formants can be influenced in the same way to a more limited extent.

It should be noted that during normal speech these muscles use only a small percentage of theirs overall working ability. Because of this, these muscles remain in place even though they change position the vocal cords and the lips, tongue and inner throat walls are used in a relatively

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bias state "Bs has been determined that during this relatively relaxed state a natural Muskelwellung typically in the range of 8 - enters 12 Hz, which was mentioned above ₆ This undulation causes a slight variation in the tension of the vocal cords and shifts in the basic pitch frequency of the voice ₉ This corrugation also slightly changes the volume of the resonance space, in particular the space assigned to the first formant, and the elasticity of the cavity walls, which causes shifts in the formant frequencies.These shifts around a mean frequency form a frequency modulation of the mean or carrier frequency ₀

It should be noted that neither the shifts in the basic frequency level of the voice nor in the Formant frequencies directly perceptible by a listener This is partly because the shifts are very small and partly because they are mainly are in the above-mentioned inaudible frequency range

To observe this frequency modulation, any of the various known methods of demodulating the frequency modulation can be used, provided that the modulation frequency is nominally 8-12 Hz and that the carrier of one of the bands within the voice spectrum is _zero

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An example of the infrasound changes discussed above can be observed in Pig · 1, in which a electrical signal recorded by a transmitted voice of a normal, unencumbered reluctant person originates. The figure shows the pulses of the amplitude modulation of the formants by a voice signal of about 190 Hzο Those appearing as amplitude fluctuations in Fig. 1 Fluctuations are amplitude representations of frequency modulations, the conversion being simple Sampling of the3 waste has been made o

To make the illustration of FIG. 1 better understood, will first of .Gedanke a "Massensohwerpunktes" of this waveform are explained ₀ Bs is möglioh, approximately the center zwisohen two extremes of a single deflection of the Aufzeiohnungsfeder in recording the waveform Figo NaOH 1 to determine. If the midpoints between the extremes of all deflections are marked and then connected approximately by a continuous curve, this results in a line that formed a duro section or a "center of mass" of the entire waveform A connection of all of these marks with a certain degree of smoothing leads to the smooth curve 13 in FIG.

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As mentioned, it has been found that the muscular arrangement that leads to the vocal cords and the cavity walls heard being subjected to a low level of muscle tension when there is little or no psychological stress generated during the examination of the examiner · This tension is for the person and also for the normal examination procedures, carried out without aids, are not more effective, but are sufficient to remove the muscle curl to reduce or practically eliminate, which are present in the unexposed test person Daduroh removes the basis for the carrier frequency changes that the infrasound frequency modulations generate

fig «2 illustrates an utterance similar to that in Fig. 1, but at a time when psychological distress has been induced. In this case sioh shows that the The waveform formed by the centers of mass has essentially no infrasohall changes that can be observed in the unencumbered utterance in FIG. 1, although all other test factors and the demodulation processes have been kept constant. For the sake of simplicity, the centers of mass are approximated in Figo 2 through the line 14 veransohaulioht ·

The use of the infrasohall waveform is important for the process, since “the voice is used as a physiological medium Evaluation of psychological stresses used, but the special Hay ·· Di · voice also provides possibilities for additional ·, detectable by instruments · displays

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of physiological changes not perceptible by the ear as a result of psychological stress These Physiological changes are also detectable by methods and devices currently in use Of the four most commonly used physiological changes mentioned above, namely brain wave patterns, heart activity, skin conductivity and breathability, affect two, namely the breathability and the heart activity, directly and indirectly Amplitude and detail of an oral utterance waveform and provide the basis for a more general evaluation the psychological stress, especially if the test situation is a sequence of spoken responses included

Figure 3 is a record made during a test in which psychological stress was induced in a female subject by having to utter a hypothetical lie in a peak voltage test. In the test, the test person was asked to choose a letter from a certain series of twelve letters and to keep in mind which letter they had chosen o They were then asked for each letter in turn whether they had chosen the letter _o She had also been instructed beforehand to answer "I did not choose this letter" for each letter, despite the fact that she had chosen a letter. Figures 3a, 3b and 3c

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together form a record of the verbal responses of the Vereuohsperson when questioned about each of the letters and show a combination of pneumographic, oardiographic and, to a lesser extent, infrasound influences.The signal for this representation has been integrated quite strongly in order to more clearly show the general Gesante effect »show the illustrated by this recording method is to form particularly useful in the determination of stress fields in experiments in which the answers longer versions that contain different words or where the trials are very long and a large number of responses require _e evaluation of these POLGEN longer designs is simplified because the complexity of the waveform is significantly reduced compared to the waveforms shown in Figures 1 and 2 "

The recording curves showing the answers to the series of twelve letters running from E to V, contain the following salient features that are indicative of physiological changes brought about by the attempted deception to be caused · A significant limitation in the answer to the letter E illustrated the voltage at the beginning of the test, which is normal in most open test situations »General this initial tension would disappear at L, if not the attitude, that is, the psychological attitude of the test subject would be such that the initial

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· "Voltage. Duroh the voltage is increased, the duroh the approaching lie comes ₀ This is the EaIl in this test ο It is deutlioh to see that the tension continues at M, IT and 0, where O is the point of! Deception is ο In addition to the observable effects of the infrasound signal, which is usually present in relaxed speech but is muted or absent in tense speech, specific, more common physiological indicators are also present and reflect the subject's changing emotional system the suppression or hyper-ventilation, the diction load and significant delays in the response time. The pneumographic influence provides the strongest indication of a relief after the deception point, since a merciful increase in the amplitude is indicated at the point at which the test subject is beyond the deception point and compensate for the reduction in the oxygen / carbonic acid exchange n begins, which had occurred from K to O _e

Starting at P is the relief given to the subject learns about the rest of the recording with tailweiser Exception from Q clearly. This can be interpreted as a momentary fear of the subject that the Relief at P may have been audibly clear to the examiner.

In addition, there are certain diction burdens that are used as a * leg for a progressive change in the individual state a

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can be rated «, this may be audible or auoh not if the test subject exercises unusual control over his or her diction in a verse, maintain a consistent speech pattern These indicators include small changes in the single syllable load and changes in the pattern of context in the various responses a »These indications are conditional largely the waveform pattern (as opposed to of the amplitude) of the individual response displays »They continuously show slight changes up to 0, the point of deception as it is not so much of the load üat the beginning of the test are influenced duroh the lower amplitude at K is illustrated, but an increasingly less complex representation up to to cause N and 0 and then suddenly to their complexity with the clear psychological relief in P. 'With the exception of the Q from those discussed above Reasons, this stress-free pattern lasts for the entire best of the experiment. "

It should be noted that the opposite formation can occur. This means that the load can be high Amplitudes and a multiform track are displayed, while the relief is illustrated by a drop in amplitude and a simpler pattern · This depends Of course, it depends on whether a particular subject responds to a given stimulus with excitement or Depression sprung. While the general ads

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may be different from loading and unloading of trial SiOH to Versuoh, they are relatively stable during any single experiment ₀ Natürlioh remains of infrasound indicator constant also attempt to Versuoh and individuals to individuals

Figures 4a, 4b and 4c are recordings of portions of the Answers in that discussed with reference to Figo 3a - ο Experiment © Figo 4a shows the individual characteristics of the words "nicht" and "Buohstabe" in the answer to the letter N «Figure 4b shows the recordings of the same two words for the letter 0 and 4c for the letter P · The recordings in FIGS. 4a-4o were made with a slightly greater film running speed than the diagrams of Fig. 3a-o included, so that each · horizontal division a much smaller period of time than in Figo 3a - ο illustrated · In addition, the electrical Signals that the running of the recording device Cause over the paper, to a much lesser extent than in Figs. 3a-ο in Figo 4a-ο integrated or filtered Therefore, it is possible in Figs. 4a - ο the properties in the individual words and especially to be observed in the vowels of each word · The diagrams are therefore pulled apart and illustrate more clearly the infrasound intrinsic shafts of the language discussed above aindo In FIG. 4a, the words show relatively little of the infrasound corrugation of the type "In ahn" shown in FIG.

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High manner occurs in Fig. 4b, which lie virtually no infrasound Curl to _0. In Figo 4o however, appears to curl back and illustrates the solution of the load which has become the subject approached to lie © is again a result, the phenomenon the relaxation of the muscles, which allows the acyclic undulations to reappear. As already emphasized above, the infrasound waveform is evident in the unencumbered utterances and strongly attenuated in the utterances under stress »

A few general comments should be made on the graphic representations discussed above will · The descriptions deal with the psyoho-physiological Relationships from some of the more significant points of view ausο Ss is known per se that the Punctures of the endocrine glands and the sympathetic and paraeympathic nervous system also in the Consider the relationships between a psyohologisohen Anreic and the various physiological responses Must be taken into account, ale play a role in the invention »you details the physiology of the Trachea and the resonance cavities of the rough and the Heads have also been dealt with above to a greater extent than in justification of what is described here Proceedings appear necessary · experts. in the field of physiology are the well-known physical ones Characteristics expected to occur in these areas *

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Although some practice and experience is highly desirable in order to recognize certain characteristics which appear in the graphical recordings mentioned above, considerably less practice and experience are required in interpreting recordings of this type compared to those previously used display units-for physiological reflexes that also the above-discussed further Naohteile have ₀ with very little practice and experience can anybody with enough intelligence policy and procedures that are discussed here. Pick up and use. " Someone who is already practiced in the field of polygraphic analysis and the use of lie detectors, which used the usual displays of physiological utterances, can use the method according to the invention in a very short time.

Regarding the graphical representations themselves the visual representation and the way in which they are produced can be better understood through a discussion of apparatuses, which are used to generate the diagrams discussed here

An embodiment of an apparatus is shown in Figo 5 »« » placed · Bin transducer 20 converts the sound waves of the mouth-watering utterances of the test subject into electrical ones Signals that are fed to the input of an audio amplifier 21, the only purpose of which is to increase the strength of the to increase electrical signals to a more stable, usable level * The output of the amplifier 21 is with

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• Intm filter 22 connected, the main one being the two hatι some undesirable low frequency components and To remove noise components

After filtering, the signal goes into an M-discriminator 23 »in which case the frequency deviations from the Büttel« · frequency can be converted into signals that fluctuate in amplitude · The amplitude change signals then sampled by a detector circuit 24 for the purpose of the Gleiohriohtung the signals and the generation of a signal, which consists of a series of half-wave pulses. gratorkreis 25 introduced, in which the signal in the the desired extent is integrated · In circle 25 the Signal either integrated to a very small extent »creating a waveform similar to dtr Training is the signal will

which is shown in Eds. 1 and 2 , or more integrated and provides a signal,

that comes closer to that of the flg. 3a - ο. After integration, the signal is amplified in amplifier 26 and a Aufzeiohnungseinriohtung 27 supplied, the one Visible diagram recording provides

This is an approximate embodiment of a facility for producing slohtable recordings according to the invention is shown in Fig. 6, The acoustic signals are converted by microphone 30 into electrical signals which are magnetically recorded in a tape recording device 31. The signals can then *

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ORIGINAL INSfHJT

by other devices at different speeds and at any time to be treated further, with the Playback device with a conventional semiconductor diode 32 connected to what the signals gleiohriohteto you Rectified signals are the input of a conventional amplifier 33 and the movable contact of a Selector, shown generally at 34 The movable contact switch 34 can be moved to any of a plurality of fixed contacts, each of which is connected to a capacitor. In Pig. 6 shows a selection of four capacitances 35-38, each of which has a connection with a fixed contact of the switch and through another connection is connected to Brde · The output of the Amplifier 33 iit bit a diagram recorder connected, since it is indicated generally at 39

lin iM sent liohen the device according to Hg · 6 «at * noticeable ·· device was iua? Irsugung you onatiohaungen used, which in din fig. 1-4 are shown. slide sohiidi between the apparitions of the Vereohiidenin grammi are duroh the difference in the playback rate of the tape recorder 31 and duroh dai Auweafl the integration requires that the choice of capacities was achieved by means of the Sohalter 34 · Dai Band »· recorder that was used in this particular arrangement of equipment was one under the designation UHER 4000 commercially available device with four Gilohwindig « keitan and your own inner reinforcer · The values of capacity

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ORIQiNAL INSPECTED

capacities 35-38 were 0.5 "3" 10 and 50 uf, the input impedance of the amplifier 33 was approximately 10000 Ghm _e The strip chart recorders that are used have a sufficient inductance to scan for the desired amount of high-frequency filtering and slope · ™ Two recorders were used, one (for Hg · 3a-c and 4a-c) a commercially available device under the name Isterlira-Angus Model 0-601 and the other a galvanometer-recorder and motorized device was from a Keeler lie detector,

When using the circuit according to FIG. 6, the rectified waveform emitted at mode 32 is integrated to the desired extent, the time constant being chosen so that the effect of the frequency-modulated infrasound wave appears as a slowly changing equal current level, the _f see Fig. 1, approximating the line indicated by "the reference numeral 13 follows" The migrations shown in this particular diagram are relatively quick and illustrate that the switch was connected to one of the capacitors of lower capacitance "Pur the daigrams 3a-c, the switch 34 would be set so that the capacitance 38 is connected to the input of the amplifier 33. "

In this embodiment, the filtering is carried out by the

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Interaction of the capacity 35 _t 36, 37 or 38, the diagram recording device, the diagram recording amplifier, and in the case of a reduction in the playback speed, the tape recording device of the diagram recorder ereiohto

The method and device described above enable a relatively simple technique of air evaluation the psychological stress of an examination period and can therefore be useful for perceiving attempts at deception Connections to the examiner are required »Therefore the apparatus can be used without a Examiner from the review; white · Furthermore is a It is also possible to check people across gaps, for example via telephone lines or others Means of communication ο An example of this method is oral recording one or more people who appear on a television program, particularly a program in which each of the three people claims a certain identity, but only one of the three people claims the truth speaks »Recordings of such statements made by each person, which according to the inventive moderate method on a device according to Figo 6 loading

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acts have been iat, provided records from which
the truth-speaking person borrowed could be found out. Accordingly, the device according to the invention is far less useful in its use than the previously known devices for analyzing load conditions

- PATENT CLAIMS -

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Claims (1)

PATENT CLAIMS soldering process to determine a psychological condition * laetung a person, characterized in that oral utterances of the person on one of the Siohtbeobaohtung accessible carrier and in the signed utterances frequency components as An ** signs of physiological embodiments of psychological stress are identified " 2 »Method according to claim I _9, characterized in that the fluctuations in the infrasound area in the utterances of the same person are compared» 3 · Method according to claims 1-2, characterized in that at least selected frequency fluctuations in the Oral utterances are converted into amplitude fluctuations and a time-dependent recording of the Amplitude fluctuations are generated, 4 · Method according to Claim 3 »characterized in that the verbal utterances are recorded magnetically 5. Method according to claims 1-3, characterized by that the sound energy of verbal utterances is converted into electrical signal energy and selective selected features of the signals embodying the utterances are highlighted and the resulting ones 209834/0794 -28- 220450] Signals with highlighted parts for observation " be asked, Method according to Claim 5 »characterized in that features which are emphasized as selected are composed Characteristics caused by the overall physiological change are used, ο Facility for displaying the properties of the Verbal utterances made by a person to observe signs of physiological embodiment psychological stress, characterized by a converter device (20) for converting the oral Utterances in electrical signals, by signal processing means that receive the electrical signals and highlight preselected properties of these signals, and by means of displaying the highlighted ones Properties,) Qo device according to claim 7 »characterized in that the transducer (30) is provided with means (31) for generating a magnetic recording of the oral utterances«, 9ο device according to claim 7, characterized in that the signal processing means a detector device (24) for determining infrasound frequency fluctuations in the oral utterance and means for displaying a variable amplitude signal which is suitable for the Is representative of fluctuations » - 29 209834/0794 ΙΟ »Equipment according to claim. 7 »characterized ₉ that the means for signal processing have means (25) for integrating the electrical signals« 11ο Device according to claim 7 *, characterized in that the means for signal processing have means (23) for highlighting composite properties based on physiological changes _e 12. Device naoh one of the preceding claims 7-11 »characterized by a demodulation device for converting frequency modulations that occur in electrical signals into amplitude modulations that are fed to the subsequent recording device » 209834/0794 ΙΟ Blank page