No abstract

A laboratory study was designed in order to investigate the effects of ventilation noise on performance, fatigue and annoyance. The study was also designed in order to compare the effects of broadband noise 40 dB(A), tonal noise, 40 dB(A), and tonal noise masked by means of low frequency pink noise, 41 dB(A). The study of performance was based on a figure identification test. The annoyance and fatigue were tested by means of rating scales. The analyses of fatigue also included EEG-recordings. The acceptability of the different types of ventilation noise was also analysed through matching tests. The differences in performance between broadband and tonal ventilation noise were significant and did not show any unambiguous tendency. An insignificant tendency of worse performance during broadband exposure and that the tonal ventilation noise should be more tiring could be observed. The tonal exposure was described as less annoying during work. On the other hand, in the matching tests, the subjects tolerated an insignificantly lower level of the tonal ventilation noise compared to the broadband noise. Comparisons between the tonal ventilation noise and the tonal ventilation noise masked by means of a pink noise, showed that the masked ventilation noise was correlated to ambiguous tendencies towards higher performance, lower fatigue but higher annoyance. In the matching tests, the subjects tolerated a lower level of masked ventilation noise compared to the unmasked ventilation noise. Except for the ratings of fatigue, all differences were below the level of significance p 0.05.

Traditional protocols for the immunohistochemical localization of peptides and tyrosine hydroxylase (TH) in nerve fibers in cryostat sections require the tissue to be thoroughly fixed and rinsed and to be processed for the cryostat sectioning and the immunohistochemical staining more or less directly after freezing. In the present study it was tested whether also unfixed, rapidly frozen tissue, conforming to guinea pig and bovine heart specimens, can be used for the visualization of neuropeptides [neuropeptide Y (NPY) and substance P (S P)] and TH in cryostat sections. The following observations were made: 1) NPY-immunoreactive (IR) and S P-IR nerve fibers could be clearly identified in both fixed and unfixed sections of this type of tissue. 2) TH-IR nerve fibers could be detected in unfixed tissue if the sections were post-fixed with aldehydes by the use of a two-step fixation process related to a sudden change of pH. However, the outlines of the nerve fibers were sometimes diffuse. 3) Storage of unfixed tissue for periods of up to 2.5 years at-80 degrees C did not lead to a decrease in immunoreactivity. 4) Somewhat higher concentrations of primary antibodies had to be used for sections of unfixed tissue than for sections of fixed tissue when the FITC method was used. This waste of antibodies was partly overcome by use of the biotin-streptavidin method. The glyoxylic acid induced catecholamine(CA)-fluorescence method for demonstration of sympathetic nerve fibers was also applied and was found to give optimal results after storage of tissue for up to 2.5 years.(ABSTRACT TRUNCATED AT 250 WORDS)

20 subjects were exposed to a tonal ventilaton noise, with the information to adjust the tone frequency at 40 dBA, to the lowest and highest annoying experiences. The adjusted frequencies were 58 and 380 Hz. The higher frequency was correlated to significant higher annoyance, discomfort and lower performance. The rated effort was higher but below the significant level of 5%. According to the investigation, lower tone frequencies are less annoying than higher. The dBA ratings thus may result in an overestimation of the annoying reactions in cases of low frequency tone components.

The present experiments were designed in order to investigate the effect of infrasound on wakefulness. 20 male subjects were exposed in a pressure chamber designed for high infrasonic sound levels. The level was adjusted to 125 dB(Lin) for the frequencies 6 Hz, 12 Hz, 16 Hz and intermittent 16 Hz. During exposure measurements were made on EEG, blood pressure and heart activity. Exposure to intermittent 16 Hz and 6 Hz were found to stimulate the appearance of drowsy states. The effect was verified through deorganization of the alpha activity in EEG and appearance of theta waves (recorded in periods of 5 minutes), lowering of systolic and diastolic blood pressure and reductions in heart frequency. On the basis of these results it is suggested that exposure to infrasound might, in some cases, be a stimulus for production of drowsy states.