Showing papers by "Barbara Griefahn published in 2006"

Executive brain functions after exposure to nocturnal traffic noise: effects of task difficulty and sleep quality

Abstract: The after-effects of nocturnal traffic noise on cognitive performance and inhibitory brain activity were investigated. Twenty participants (18-30 years) performed an easy and a difficult visual Go/Nogo task with simultaneous EEG recording after a quiet night and then during three nights when aircraft noise was presented with equivalent noise levels of 39, 44, and 50 dBA, respectively, between 11 p.m. to 7 a.m. Based on subjective sleep quality rating, participants were separated into "good" versus "bad" sleepers. The performance and inhibition-related components (N2, P3) of event-related potentials were analysed. The N2 and P3 amplitudes were smaller and latencies were prolonged in the difficult than in the easy task. This effect was more pronounced for Nogo than for Go trials. The Nogo-P3 amplitude was smaller in Noise than in "Quiet" conditions in the difficult task only. In the difficult task, the Nogo-P3 latency was prolonged in bad sleepers than in good sleepers. The Nogo-P3 amplitude was reduced in Noise as compared to "Quiet" conditions in bad sleepers only. Sleep quality in bad sleepers worsened steadily with increasing noise levels. No effects of noise or subjective sleep quality on performance were found. Inhibitory processes appear to be selectively impaired after nocturnal noise exposure. The task difficulty and perceived sleep quality are important factors modulating noise effects. The results suggest that nocturnal traffic noise increase physiological costs for inhibitory functioning on the day even if no overt performance decrement is observed.

Shifts of the hormonal rhythms of melatonin and cortisol after a 4 h bright-light pulse in different diurnal types.

Abstract: If applied during corresponding times of the individual melatonin profiles, bright light shifts the circadian phase equally, irrespective of diurnal type. We examined 32 young men: 10 morning types, 11 evening types, and 11 with no predisposition; 16 with high and 16 with low melatonin production. Each completed a 40 h session that included two consecutive nights during which the participants remained, apart from two short breaks during the second day, in bed under an illumination level of 30 lux. A 4 h bright light pulse was applied just after the expected individual melatonin onset the first night to cause a delay of the hormonal profile the second night. Salivary levels of melatonin and cortisol were determined hourly. Melatonin was delayed by 108 min, and cortisol offset and onset by 47 and 110 min, respectively. The cortisol quiescent period (start and end of the quiescent period being defined by the decrease below and the increase above 60% of the average cortisol production between 18:00 and 09:00 h) was prolonged. In contrast to the other subgroups, the delay of melatonin synthesis was about 0.5 h shorter in morning types, and their cortisol quiescent period was shortened. The present study leads to the hypothesis that, despite individually scheduled light exposure, morning types are potentially disadvantaged due to elevated cortisol levels, if persisting, in career night workers.

The tram bonus

Abstract: The annoyance of three different sound sources was evaluated in a psychoacoustic experiment. An objective analysis of the stimuli used in the experiment has shown that calculated loudness was responsible for equally annoying pairs of different sound sources. Based on the loudness calculations and annoyance ratings, a "tram bonus" of 3 dB was found in comparison to the bus sound source. In addition, it was found that loudness explains the annoyance results when the LpA max is larger than 74.5 dB(A). With sound levels smaller than 74.5 dB(A) sharpness and roughness contribute to annoyance judgments.

Awakenings related to noises from various traffic modes

Abstract: AIM: To test the hypothesis that aircraft noise causes more awakenings and alterations of sleep structure than rail and road traffic noise. METHODS: 12 women and 12 men (19-28 years) slept, following a habituation night, 4 nights each during 3 consecutive weeks in the laboratory. They were exposed with weekly changes to road-, rail-, or aircraft noise. Each week consisted of a random sequence of a quiet night and 3 nights with equivalent noise levels of 39, 44 and 50 dBA indoors. The polysomnogram was recorded throughout all nights, sleep quality was assessed and performance tests were completed in the morning. RESULTS: Noise-induced awakenings and structural parameters of sleep, subjective quality and performance indicated more disturbances with increasing noise levels. Where decreased subjective sleep quality was not related to the type of noise, noise-induced awakenings and other physiological parameters of sleep were most affected by rail and least by road traffic noise. CONCLUSIONS: As road-, rail- and aircraft noise caused the same after-effects but different physiological effects integrated noise metrics might be suitable for the prediction of subjective sleep quality but not for the physiological disturbances of sleep.