Møller, Henrik

VBN (Videnbasen)  Aalborg Universitets forskningsportal

    Aalborg UniversitetThe influence of infrasound on task performanceMøller, HenrikPublished in:Proceedings of Conference on Low Frequency Noise and Hearing, Aalborg, Denmark, May 7-9, 1980Publication date:1980Link to publication from Aalborg UniversityCitation for published version (APA):Møller, H. (1980). The influence of infrasound on task performance. In Proceedings of Conference on LowFrequency Noise and Hearing, Aalborg, Denmark, May 7-9, 1980 (pp. 85-94)General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            ? Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            ? You may not further distribute the material or use it for any profit-making activity or commercial gain            ? You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access tothe work immediately and investigate your claim.Downloaded from vbn.aau.dk on: April 29, 201785 Conference on Low Frequency Noise and Hearing 7-9 May 1980 at Aalborg University Centre Aalborg, Denmark Proceedings edited by Henrik M011er and Per Rubak THE INFLUENCE OF INFRASOUND ON TASK PERFORMANCE. Henrik M¢ller Institute of Electronic Systems Aalborg University Centre Postbox 159, DK-9100 Aalborg Denmark . Sununary. 16 subjects were exp osed to infrasound and traffic noise while task performance measurements were carried out . Infrasound above the hearing threshold level (120 dB) seems to affect human task performance. An addition duty was carri-ed out 7% s lower, and the reaction time in a complex reaction time test was increased 6% . In a cue utilization test there were 80% more errors . Traffic noise at L = 71 dB (A) sho-wed no effects . eq Introduction . It has often been claimed that infrasound coul d infl uence hu-man performance. Most observations of this kind are from hu-man everyday environment, where both the exposure and the ob-servation of the performance are uncertain . Therefore labora-tory experiments are needed where the exposure is wel l known (infrasound without vibrations, audio frequency sound etc.), Proceedings of the Conference on Low Frequency Noise and Hearing 7-9 May 1980 in Aalborg, Denmark 86 and where a number of well defined performance parameters are recorded. Experiments like these have been carried out [1-10] but the results are not very concordant , and further investi-gation is needed. This i nves t igation deals with both physiological parameters, task performance and subjective annoyance impressions, but only the task performance recordings have been analysed until now, and they will thus be t he on ly subject of this paper. Exposure. The experiments were carried out i n an infrasound test cham-ber built at Aalborg University Centre [11,12]. The chamber is rather large, 1 6 m3 , in order to avoid psychological re-actions from the subjects. The infrasound is generated by 16 l arge electrodynamic l oudspeakers. To allow experiments of long duration the test chamber is equipped with a ventilat-ing system. Four different exposures were used. In addition to two infra-sound signals, a "quiet" exposure was used, and for compara-tive reasons , an audio frequency noise. A - quiet. B - traffic noise . This was a recording from a main road in Aalborg. The playback level was L = 71 dB(A). eq C - low level infrasound, see figure 1. Total SPL=lOO dB. D - high level infrasound, see figure 1 . Total SPL=l20 dB. C and D were broadband infrasound signals, frequency shaped along the treshold curve 5-25 Hz, which makes the "low" and "high " frequencies equal l y audible. The t otal spectrum C is hardly a udib le, while D is subjectively loud. Recordings o f task performance. 9 different task performance measurements were used. The tests consisted of duties presented either on a small film viewer or on a CRT- display terminal. The duties were answer-Proceedings of the Conference on Low Frequency Noise and Hearing 7-9 May 1980 in Aalborg, Denmark 120 dB SPL llO 100 90 80 70 60 50 40 87 Figure 1. 1/3 octave analysis •• D ~~gg§§§§§§~f!~~ija~ of the stimuli I: C C and D. 2 Hz 4 8 16 31. 5 Total SPL: C: 100 dB D: 120 dB ed by pressing pushbuttons. Some of the tests were developed at The Laboratory of Heating and Air Conditioning at The Technical University of Denmark, where the purpose was mea-surement of task performance during exposure to different conditions of tempe rature , humidity of air and t he like [13]. In the tests the answering of o ne duty was immediately fol-lowed by presentation of the next one . Test 1 consisted o f addition duties. 5 three-digit numbers should be added . Three suggestions of the sum were present-ed and the subject should choose between these or indicate , that none of them were correct. The four answers were equal -ly probable. In test 2 nine two-digit figures were presented and the sub-ject should indicate whether they were a ll different. In 34% of the presentations two or more figures were identical. I n test 3 logical statements of a certain construction were presented. The subject shoul d indicate whether the statement was right or wrong. Proceedings of the Conference on Low Frequency Noise and Hearing 7-9 May 1980 in Aalborg, Denmark 88 Exempl es : A precedes B: AB (right) After A is C: CA (wrong) c does not follow B: CB (right) A is not before B: AB (wrong) Test 4 was a cue utilizat i on test ; a mod ified version of the Tsai-Partington test (14) . The order l -A-2-B- 3-C-4-D etc. should be followed, and the subject was to indi cat e whether the next sign could be found, see figure 2 . Q) ® ® @ ® @ @ ® @ © @® ® Figure 2 . Example of test 4 . Test 5 was a short time memory test. A l ist of words was pre-sented, one word at a time . Each word might occur more than once and the person should indicate whether he had seen it b efor e. Test 6 was a simple reaction time test . When a l etter appea-red in the centre of the CRT display a pustbutton should be pressed . The time from a n swering t o presentatio n of t he next stimulati on was random b ut unifor mly distributed in the range 2-6 seconds. In test 7 t he d i splay was divided into five pa r ts and the l etter E appeared i n one of them every 2 seconds . The subject should react only on appearance in the cen tre . In test 8 the display was divided into two parts by a verti-cal line . The lett ers E and F could appear one at a time at e i ther the left or the right side . The subject should only Proceedings of the Conference on low Frequency Noise and Hearing 7- 9 May 1980 in Aalborg, Denmark C9 r eact on an F to the left or an E t o the r i ght . Test 9 was simular to test 2, but carried out with other equ i pment . Experimental design. 15 yo ung s tudents and one person of 43 years were used as subjects, ha l f of each s ex. During two months they all parti-cipated in the experiment four days, each day for 4 hours. In a 4-hour setting 3 hours were used for exposure to one o f the four conditions g i ven above . The subj ects participated two at a time and they were all exposed to al l four conditi-ons, although not in the same order. A latin square design was used in order to balance ou t learning effects , see table I. person number : 1-4 5- 8 9-12 13-16 1. exposure : A B c D 2. exposure : B c D A 3 . exposure : c D A B 4. exposure: D A B c Table I . Lati n square design of the .expe riments. For each setting a strict time table was used , see figure 3 . Results. From the t ests were recor ded mean response time and percents of e rrors (except test 6, where only the response time was recorded) . It is not surprising that the quantities differ strongly from person to person . Therefore all values are normalized, which means that they are d ivided b y t he total mean for the person in that particular test . For each sound stimulus mean values and standard deviations o f the normalized variables ar.e cal-culated. For the r esponse t imes results are shown i n figure 4. Proceedings of the Conference on Low Frequency Noise and Hearing 7-9 May 1980 in Aalborg, Denmark Time: Oh OOm Oh 30m lh oom l h 30m 2h OOm 2h 30m -Jh OOm 90 Activiti es for t he first person: f audiometrical measurement fixing e l ectrodes etc . for physiological measurements . test 6 , 7 , 8 , 9 t est 4 t est 2 measuremen t of test 3 test 5 t est 6 , 7 ' 8 , 9 measureme nt of test 1 Activities f or the second person : fixing electrodes etc. for physiological measurements audiometrical measur ement test 1 blood pr essure test 6, 7, 8 , 9 t est 4 t es t 2 b l ood pressure test 3 t est 5 test 6 , 7 , 8 , 9 measurement of blood pressure questionnaire for s~bjective impressions audiometri cal measurement taki ng off electrodes taking off electrodes audiometrical measur ement Figu re 3 . Time table for e ach 4-hour e xperiment . Proceedings of the Conference on Low Frequency Noise and Hearing 7-9 May 1980 in Aalborg, Denmark (/I 0 c: :i 0. (/I "' ..... El c: ..... "' rt .... 0 :i 1,20 -Test 1 -'l'est 2 T I Test 3 1,10 1,00 " 0,90 I 'f'A a 0 "' ~ 1 (!) 0,80 J F=2,60 J F=l,08 J .L I F=l,32 a. 5· co sign.: 6% .. !2. .... 5-1,20 -, Test 4 T -Test 5 -Test 6 I"' <O () s: g 1,10 "' -'< ~ ~(!) 1,00 ~g I 1 I I l I 1 i I 1 l T 1 i T "' -· 0 0,90 I-' "" )> r "'0 0,80 J g~ F=0,16 J F=0,87 J F=0,56 ~~ (!) o"' "'c ""' 1,20 -Test 7 Test 8 I Test 9 3 i5 "' '< x-z 1,10 0 iii' Cl> "' 1,00 " a. :i: 0,90 Cl> !!l 5· 0,80 J F=2,90 J ~ F=2,02 co ..J 1 .L F=2, 5il sign.: 4% sign.: 6% Figure 4. Hean values (x) and standard deviation (vertical bars indicate : 1 s.d. l of the normalized response times. F values and significance levels: see text. 92 I t is quite obvious t hat no gener al deterioration in the per-formance caused by the sound stimuli in B, C and D can be seen from the figure. According to the mean values , the sub-jects worked faster in some tests and slower in others, when exposed to noise. Before making any conclusions about the influence of the noi-se on performance it is important to clarify whether the ob-served differences are so large that they cannot be explained as random. For this purpose a one way analysis of variance has been carried out. In this analysis the H0 hypothesis is: the mean values are all equal . The significance level indica-t es the probabil ity of obtaining the observed results or va -lues that differ even more if H0 were true. F values and sig-nificance levels from the tests are indicated in figure 4. In test 1, 7 and 9 H0 is rejected at 6%, 4% and 6% level, re-spectively. Only results from these tests are further analys-ed . In simple t-tests the values from B, c and D are compared to values in A. The foll owing is observed : Test 1: the response time is longer in D (significant at 2% level). Test 7: the response time is longer in D (3% level). Test 9 : the response time is shorter in C (2% level). The values of the error percents were a nalysed in a similar way . The analysis of variance only showed significant diffe-rences in test 4, and here there were 80 % more errors in D than in A (significant at 1% level in a t-test) . Discussion. In test 9 an improvement was shown when the subjects were ex-posed to noise C. However, this seems very unlikely, and as test 9 is similar to test 2 where no significant changes were seen, the significance was probably random . Except for the above mentioned, all alterations in performan-ce appeared as deteriorations when t he subjects were exposed to noise D. This seems to indicate that infrasound above the Proceedings of the Conference on Low Frequency Noise and Hearing 7-9 May 1980 in Aalborg, Denmark 93 threshold value is able to affect task performance in a ne-gative way. It is remarkab l e that no significant changes were seen when the subjects were exposed to traffic noise (B). This indica-t es that the recorded parameters are not very susceptible to noise. Traffic noise at Leq = 71 dB is subjectively rather disturbing, and the results seem to show that the human be-ing - at least for a few hours - is able to compensate for this, so tasks are carried out without deterioration. Thus task performance measurement may be a poor tool in noise assessment. With this in mind, the significant deteriorations in perfor-mance caused by audible infrasound may be regarded as being more serious than their magnitude immediately seems to indi-cate. In the present design o f the experiment (latin square) the learning effect is balanced out, but i t still contributes to the standard deviation. A further study of this effect might lead t o a compensation giving smaller standard deviations and thus more significant changes in performance . Acknowledgements. The author wishes to acknowledge the important assistance of M. Sc. Gunnar Langkilde, B. Sc. Bjarne Kirk and B. Sc. Anders B. Mort ensen. References. 1 . c . STANLEY HARRIS , DANIEL L. JOHNSON : Effects of infra-sound on cognitive performance. Aviation, Space and En -vironmental Medicine, vol. 49 , no . 4 , 582- S B6 , 1978 . 2. PHILIP M. EDGE, WILLIAM H. MAYES : Description of Langley low- frequency noise facility and study of human response to noise frequencies below 50 cps . NASA Technical Note D-3204, National Aeronautics and Space Administration , Washington D. C., January 196C . 3. BOB R. ALFORD, JOHN BILLINGHAM, A.C. COATS, B.O. FRENCH, JAMES F. JERGER, R.O. McBRAYER: Human tolerance to low frequency sound. Transactions of American Academy of Ophthalmology and Otolaryngology, vol. 70, 40- 47, 1966 . Proceedings of the Conference on low Frequency Noise and Hearing 7-9 May 1980 in Aalborg, Denmark 9 4. 4 . R.A . HOOD , K. KYRIAKI DES , H. G. LEVENTHALL : Some subjec -tive effec ts of no i se . British Acoustical Soci ety Meeting on In frasou nd, 26th November 1971 , University of Sal f ord, l .971. 5. H. G. LEVENTHALL : Man- made infr asound - its occur rence and some subj e ctive effect s . Colloque International sur Zes Infra-sons , 24- 27 Septembre 1973 , Paris . Proceedings edi -ted by L. Pimonow, 129- 152, l.97i . 6 . K. KYRI AKI DES , H. G. LEVENTHALL : Some effects o f infrasound on task p e rformance . Journ al of Sound and Vibration, vol. 50, no. 3 , 36.9 - 388, 197'1 . 7. J . MARGARET EVANS, W. TEMPEST: Some effects of infrasonic noise in transportation. Journal of Sound and Vibration, vol. 22 , no . 1 , 19- 24 , 197!!. 8 . PAUL BORREDON, JEAN NATHIE: Effets physio logiques observes chez l ' homme expose a des niveaux infrasonores de 130 dB . Colloque International sur les In frasons, 24 -2 7 Septembrc, Paris . Pro ceedings edited by L.Pimonov , 61 - 84 , 1973. 9. PAUL BORREDON, A. GI BERT, JEAN NATH I E: Etude chez l'homme des effet s physio l ogiques d ' une exposition a des niveaux infrasonores de 130 dB. AGARD conference no . 145 "Fibr·a-tion and combined stres s es .in advanced systems" , Oslo 22 . -2:5 . april 1974 . (£'ditor: H. E. von Gierke ). 10 . R.J. ALFREDSON, N. BRONER, T.J. TRI GGS : Low frequency noise a nd testing for i t s effects. Vibra t ion and No is e Control Engineering Conference , Sydney 11 - 12 October 1976 . The In -stitution of Engineers , Australia . National Conference Pub -lication no . ?6/9 . 11 . HENRIK M0LLER: Construction of an infrasound test chamber (in danish). R-77-8, Institute of Electront'.c Sy stems, Acil-borg Universi ty Centre , November 197 7 . 12 . HENRIK M0LLER: Infrasound project at Aalbo rg University Centre. Institute of Acousti~s Meeting on Low Frequency Noise , ~th January 19 7P, Chelsea College , London . 13. GUNNAR LANGKILDE: The i nfluence of the thermal environ-ment on offi ce work . In P.O.Fanger and O.Valbj¢rn (Eds.): Indoor Climate , Danish Building Research Institute, Copen -hagen 1979, pp . 835 -856 . 14. C.H. AMMONS: Tasks for study o f percept ual learning and performance variables. Percept . Mot. Skills , vol. 5, 11 -14, 197 5. Proceedings of the Conference on Low Frequency Noise and Hearing 7- 9 May 1980 in Aalborg, Denmark 

The influence of infrasound on task performance

http://vbn.aau.dk/files/227874424/1980_M_ller_LF_conference.pdf

The influence of infrasound on task performance

Abstract

Similar works

Full text

Available Versions

VBN (Videnbasen) Aalborg Universitets forskningsportal