Does Low Frequency Noise at Modarate Levels Influence Human Mental Performance?

The aim of this study was to assess the influence of low frequency noise (LFN) at levels normally occurring in the industrial control rooms on human mental performance (attention, visual perception and logical reasoning) and subjective well-being. Subjects were 191 male volunteers categorised in terms of subjective sensitivity to noise in general. They performed standardised tests: the Signal Detection Test (test I), the Stroop Colour-Word Test (test II), and two sub-tests of the General Aptitude Test Battery, i.e. the Math Reasoning Test (test III) and the Comparing of Names Test (test IV). Three different acoustic conditions were used in the between-subjects design: the background laboratory noise of about 30 dB(A), LFN, and a broadband noise without dominant low frequency components (reference noise) at 50 dB(A). Each subject was tested only once in random-assigned exposure conditions. Generally, no significant differences in performance related to exposure conditions were noted. Some of the results from test I and test II were influenced by sensitivity to noise. However, there were no significant differences between high- and low-sensitive subjects during exposure to LFN. The annoyance of LFN and reference noise was rated higher than that of the background noise. Subjects highly-sensitive to noise reported higher annoyance due to LFN in comparison with low-sensitives. No significant differences related to noise sensitivity in annoyance assessment of background and reference noises were noted. In conclusion, no effects due to LFN on mental performance compared to background and reference noises were found.

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How Can Low-Frequency Noise Exposure Interact with the Well-Being of a Population? Some Results from a Portuguese Municipality

Applied Sciences ◽

10.3390/app9245566 ◽

2019 ◽

Vol 9 (24) ◽

pp. 5566 ◽

Cited By ~ 1

Author(s):

Juliana Araújo Alves ◽

Lígia Torres Silva ◽

Paula Remoaldo

Keyword(s):

Urban Areas ◽

Noise Exposure ◽

Low Frequency ◽

Noise Pollution ◽

Well Being ◽

Sound Level ◽

Frequency Noise ◽

Low Frequency Noise ◽

Sound Levels ◽

Exposed Population

Noise pollution is the second most harmful environmental stressor in Europe. Portugal is the fourth European country most affected by noise pollution, whereby 23.0% of the population is affected. This article aims to analyze the effects of exposure to low frequency noise pollution, emitted by power poles and power lines, on the population’s well-being, based on a study of “exposed” and “unexposed” individuals in two predominantly urban areas in north-western Portugal. To develop the research, we used sound level (n = 62) and sound recording measurements, as well as adapted audiometric test performance (n = 14) and surveys conducted with the resident population (n = 200). The sound levels were measured (frequency range between 10 to 160 Hz) and compared with a criterion curve developed by the Department for Environment, Food and Rural Affairs (DEFRA). The sound recorded was performed 5 m away from the source (400 kV power pole). Surveys were carried out with the “exposed” and “unexposed” populations, and adapted audiometric tests were performed to complement the analysis and to determine the threshold of audibility of “exposed” and “unexposed” volunteers. The “exposed” area has higher sound levels and, consequently, more problems with well-being and health than the “unexposed” population. The audiometric tests also revealed that the “exposed” population appears to be less sensitive to low frequencies than the “unexposed” population.

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Broadband low-frequency noise reduction using Helmholtz resonator-based metamaterial

Noise Control Engineering Journal ◽

10.3397/1/376932 ◽

2021 ◽

Vol 69 (4) ◽

pp. 351-363

Author(s):

Jhalu Gorain ◽

Chandramouli Padmanabhan

Keyword(s):

Transmission Loss ◽

Low Frequency ◽

Helmholtz Resonator ◽

Broadband Noise ◽

Unit Cell ◽

Frequency Noise ◽

Noise Attenuation ◽

Low Frequency Noise ◽

Low Frequencies ◽

Pu Foam

Achieving broadband noise attenuation at low frequencies is still a significant challenge. Helmholtz resonators offer good low-frequency noise attenuation but are effective only over a narrow band; the cavity volume required at these frequencies is also larger. This article proposes a new broadband acoustic metamaterial (AMM) absorber, which uses polyurethane (PU) foam embedded with small-size resonators tuned to different frequencies. The AMM design is achieved in three phases: (1) develop a transfer-matrix-based one-dimensionalmodel for a resonator with intruded neck; (2) use this model to develop a novel band broadeningmethod, to select appropriate resonators tuned to different frequencies; and (3) construct a unit cell metamaterial embedded with an array of resonators into PU foam. A small-size resonator tuned to 415 Hz is modified, by varying the intrusion lengths of the neck, to achieve natural frequencies ranging from 210 to 415 Hz. Using the band broadening methodology, 1 unit cell metamaterial is constructed; its effectiveness is demonstrated by testing in an acoustic impedance tube. The broadband attenuation characteristics of the constructed unit cell metamaterial are shown to match well with the predicted results. To demonstrate further the effectiveness of the idea, a metamaterial is formed using 4 periodic unit cells and is tested in a twin room reverberation chamber. The transmission loss is shown to improve significantly, at low frequencies, due to the inclusion of the resonators.

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