Effects of low intensity noise from aircraft or from neighbourhood on cognitive learning and electrophysiological stress responses.

The effects of low intensity noise on cognitive learning and autonomous physiological processes are of high practical relevance but are rarely addressed in empirical investigations. This study investigated the impact of neighbourhood noise (of 45 dB[A], n=20) and of noise coming from passing aircraft (of 48 dB[A] peak amplitude presented once per minute; n=19) during computer based learning of different texts (with three types of text structure, i.e. linear text, hierarchic hypertext, and network hypertext) in relation to a control group (35 dB[A], n=20). Using a between subjects design, reproduction scores, heart rate, and spontaneous skin conductance fluctuations were compared. Results showed impairments of reproduction in both noise conditions. Additionally, whereas in the control group and the neighbourhood noise group scores were better for network hypertext structure than for hierarchic hypertext, no effect of text structure on reproduction appeared in the aircraft noise group. Compared to the control group, for most of the learning period the number of spontaneous skin conductance fluctuations was higher for the aircraft noise group. For the neighbourhood noise group, fluctuations were higher during pre- and post task periods when noise stimulation was still present. Additionally, during the last 5 min of the 15 min learning period, an increased heart rate was found in the aircraft noise group. Data indicate remarkable cognitive and physiological effects of low intensity background noise. Some aspects of reproduction were impaired in the two noise groups. Cognitive learning, as indicated by reproduction scores, was changed structurally in the aircraft noise group and was accompanied by higher sympathetic activity. An additional cardiovascular load appeared for aircraft noise when combined with time pressure as indicated by heart rate for the announced last 5 min of the learning period during aircraft noise with a peak SPL of even 48 dB(A). Attentional mechanisms (attentional control) like being threatened by passing aircraft approaching the airport, higher demands of selective filtering, and difficulties in changing cognitive strategies during noise are discussed as underlying mechanisms.