Noise as stress-inducing factor

Based on the stress model according to LAZARUS AND L^AUNIER (1981) (see Fig.2.8), every perceptive process indicates a stimulus situation which is allocated a corresponding significance on the basis of personal evaluation. When one perceives stimuli that differ significantly from a currently perceived pattern, e.g. a flashing light in ones visual range or a particular sound, e.g. a car horn in ones acoustic range, an orientation response is generally the result. This is associated with the directing of ones attention to that signal.

Associated with this reaction is a short-term activation on a physiological level. In a (very simplified) explanation according to SELYE (1981) the hypothalamus and the hypophysis release the two stress hormones adrenalin and cortisol, which in turn increase the overall physical activity on both motor and cognitive levels. If one refers back to the evolutionary process 500,000 years ago, this was certainly necessary for survival. However, in our present time the reaction possibilities have changed somewhat.

The result of an initial evaluation of the stress-inducing factor, in this case "relevant“

or "irrelevant“, then possibly leads to an all clear signal or to a further activation in order to deal with the stress-inducing factor. While the intensity of the stimulus as compared to the actual environment is one key factor for the triggering of the stress process, the other is the result of the evaluation of the stimulus. Hearing ones own name in a conversational environment also leads to an orientation reaction, even if the speaker's volume is no different from the general noise level. The signal content is the significant factor in this case. The result of a second evaluation, should the first have proved "relevant“ determines the subsequent processing. At this point the actual resources are tested with the possible results "will certainly be overcome", "to be seen as a challenge" or "I have insufficient options". Further interaction with the stress-inducing factor and therefore the reaction now depend on this outcome. At this point, coping strategies are brought into play, which may lead to the stress being overcome, as illustrated by KRETSCHMANN or SCHAARSCHMIDT AND FISCHER. This does not however concern the search for causal relationships.

The particular feature of this model of psychological stress is that it describes a continuously ongoing process, as indicated by the revaluation point in Figure 2.8.

With respect to the stress-inducing factor "noise“ this might mean that long-term noise, which is perceived as annoying but from which one cannot remove oneself nor immediately counteract, remains a stress-inducing factor with all its physiological effects and sometimes with increasing effect. This stress model is also described as

a transactional model. It describes the mutual interaction between the subject and the environment. The individual’s behaviour and the reaction can actually change the surrounding situation if only through an emotional response. (The teacher who is annoyed by noise may communicate this to the pupils purely by facial expression and possibly thereby trigger an initial reaction.)

sensation 1st assesment action

2nd assesment

Human being

time behavior

noise climate

???

fatigue action assesment

???

f(B1) f(B2)

phasic part

tonic part tonic part (new)

Fig. 2.8 Stress model according to LAZARUS AND L^AUNIER (1981)

The physiological reactions to noise, as described in occupational psychology (ROHMERT AND RUTENFRANZ, 1983), encompass the whole spectrum of possible stress reactions with regard to, e.g. the vegetative nerve system, hormone system, cardiovascular system, motor system, perception and digestion. However, no stimulus-specific reaction pattern has been found. Personal reactions vary greatly even in identical noise structures. Noise processing evidently varies greatly between individuals therefore, and is possibly a result of the respective learning and/or socialisation processes related to ones experience or interaction with noise. The reactions that one can observe correspond to the organism's natural process of dealing with this stress-inducing factor. This has been demonstrated in many laboratory experiments. However, the question as to whether there is a possible summative long-term effect is as yet unanswered. The possibility of chronification, while it is constantly referred to in the literature, has not yet been verified.

With respect to noise in schools, FLOSS (1964) reports on of vocational college pupils from various educational areas and their reaction to noise in teaching. He observed changes in the areas of "reflex stimulation, finger tremor, body temperature and heart rate“. After 6 hours of teaching at a noise level of 62 to 71 dB(A) the error rate in a fine motor task rose by 18 % (increased finger tremor) but by only 11 % at a noise level of < 40 dB(A). Under the same conditions the body temperature rose in the first case by +0.16 °C, and sank in the second by –0.22 °C. With respect to the stress reaction based on heart rate he observed a relationship with noise level at the place of education. Metalworking pupils experienced no change in stress during loud lessons while technical drawing pupils displayed fatigue to a degree of 4 beats per minute and grammar school pupils by 12 beats per minute. This clearly shows the influence of "normal" working conditions. Another investigation by DÖRING ET AL.

(1971) on infants showed no initial reaction in the range 60-65 dB(A). It measured the change in skin blood flow and revealed a steady reduction of the blood flow (stress reaction) at noise levels above 70 dB(A). However, the threshold reduced in the case of repeated exposure wherein a reaction pointing to an increasing sensitivity to noise was observed. A long term learning process with regard to the interaction with noise was excluded in this case.

The significance of personal coping strategies, particularly with respect to further possible influential factors, is illustrated by SUST AND LAZARUS in Figure 2.9(1997).

The phasic percentages of this stress process are presented here as dysregulation, which could become however e.g. chronic dysregulation if influential factors remain unchanged. On the somatic level this is cited as an increased risk for diseases of the cardiovascular and digestive systems.

Noise:

- sound pressure level - frequency

- passage of time - duration

Factors of influence:

- time pressure - responsibility - attentiveness - noise sensitivity - state of health

Influence of

physiological and psychological regulation mechanisms

dysregulation

chronical dysregulation

Fig. 2.9 Stress-inducing effects of noise, modified according to S^{UST AND} L^AZA

-RUS, 1997

At this point it is worth mentioning once again the workplace model of the school illustrated at the start according to RICHTER AND H^ACKER who introduced the term, redefinition of the task. In the illustration of SUST AND LAZARUS the redefinition changes the influence of physiological and psychological regulation mechanisms and therefore within the scheme belongs to the group of influential factors. This central control mechanism is jointly responsible for the course of the subsequent stress processes. This model, like the previously illustrated model according to LAZARUS, is understood as a continuously repeating process, which leads in the short-term to dysregulation as a phasic reaction and to possible chronic dysregulation in the long term. In their investigations into personality structures of teachers, SCHAARSCHMIDT AND F^ISCHER (2001) found characteristics which are amongst the influential factors in the above model but which are also operative in the control mechanism of the influence. The significance for the further processing of stress is clear.

In general, research activities relating to the impact of noise on individuals are concerned with the influence of environmental noise g. traffic noise or machine noise.

In her investigations STÖLZEL (2004) cites a series of results on the impact of noise

on physiological function but also shows that the reaction is personal. Ideally the effects on the sleep of the person are documented in which case a slight noise level of 45 to 55 dB(A) can cause interference. (Even less in some cases. One only has to think of a fly buzzing around ones head in the summer or a dripping tap). In his investigations BERG (2001) shows that a reduced reverberation time against a background of normal environmental noise considerably improved the sleep quality of the test subjects with no changes to the external noise situation.

Fig. 2.10 An overview of aural and extraaural noise effects Extract from: Lexikon der Psychologie (lexicon of psychology) (2001)

The aural effects of noise are illustrated in the relevant occupational science literature in the form of "noise-related hearing impairment“. ISING ET AL. (1996) provide an overview-style summary and therefore this subject will not be covered further in this context.

In summary it is possible to determine that noise-related hearing impairment with irreversible hearing loss (TTS) is the only illness for which a causal relationship with noise exposure can be claimed. In any case, however, noise as a stress-inducing factor has physical and psychological effects, both momentary and long term. Figure 2.10 shows a range of interference types on the physiological, communication and cognitive levels. It shows clearly that even sounds below 40 dB(A), which are not normally described as noise, are observed at least as altering sleep and thus interfering with the normal cycle of events. The subjective evaluation of the annoyance and/or interference is thus a very individually varied process as clearly shown in the modified stress model (Fig. 2.9) according to S^{UST AND} L^AZARUS (1997).

If one considers the findings in the section 2.1.1 concerning the impact of noise on cognitive processes together with the stress reactions illustrated here, one obtains a clear picture of the causal relationship between physiological changes and the

resulting cognitive changes. Even from the aspect of the improvement of the cognitive preparedness for action caused by stress processes, as described by S^ELYE (1981), this is only related to an increased attentiveness to the stress-inducing factor and not the other processes such as, for instance, solving a mathematical problem or saving information just heard. In this case, the stress reaction is undesirable even if "necessary for survival" from an evolutionary perspective.