Browsing by Author "Bakker H"

Now showing 1 - 6 of 6
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    Acoustics and Biological Structures
    (InTechOpen, 2019-04-25) Alves-Pereira M; Rapley B; Bakker H; Summers S; Fellah, ZEA; Ogam, E
    Within the context of noise-induced health effects, the impact of airborne acoustical phenomena on biological tissues, particularly within the lower frequency ranges, is very poorly understood. Although the human body is a viscoelastic-composite material, it is generally modeled as Hooke elastic. This implies that acoustical coupling is considered to be nonexistent at acoustical frequencies outside of the human auditory threshold. Researching the acoustical properties of mammalian tissue raises many problems. When tissue samples are investigated as to their pure mechanical properties, stimuli are not usually in the form of airborne pressure waves. Moreover, since the response of biological tissue is dependent on frequency, amplitude, and time profile, precision laboratory equipment and relevant physiological endpoints are mandatory requirements that are oftentimes difficult to achieve. Drawing upon the viscoelastic nature of biological tissue and the tensegrity model of cellular architecture, this chapter will visit what is known to date on the biological response to a variety of different acoustic stimuli at very low frequencies.
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    Acoustics and biological structures
    (IntechOpen, 2018) Bakker H; Alves-Periera M; Summers S; Rapley B
    Within the context of noise-induced health effects, the impact of airborne acoustical phenomena on biological tissues, particularly within the lower frequency ranges, is very poorly understood. Although the human body is a viscoelastic- composite material, it is generally modeled as Hooke elastic. This implies that acoustical coupling is considered to be nonexistent at acoustical frequencies outside of the human auditory threshold. Researching the acoustical properties of mam- malian tissue raises many problems. When tissue samples are investigated as to their pure mechanical properties, stimuli are not usually in the form of airborne pressure waves. Moreover, since the response of biological tissue is dependent on frequency, amplitude, and time profile, precision laboratory equipment and relevant physi- ological endpoints are mandatory requirements that are oftentimes difficult to achieve. Drawing upon the viscoelastic nature of biological tissue and the tensegrity model of cellular architecture, this chapter will visit what is known to date on the biological response to a variety of different acoustic stimuli at very low frequencies.
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    Analysis of the stochastic excursions of tumbling apples
    (1/09/2021) Flemmer C; Bakker H; Flemmer R
    There are strong economic pressures to improve automated inspection of apples. A considerable difficulty, acknowledged in the literature, but not adequately quantified, is the question of the extent to which the surface of apples, tumbling randomly on rollers, is covered by camera views during inspection. This work demonstrates a method to measure the roll, pitch and yaw of tumbling apples by tracking features on the skin between succeeding camera images and then to use the measured data to provide precise statistical descriptions of the tumbling process. The method was tested on an image library of four apple varietals; Eve and Granny Smith, which have mostly uniform skin colour, and Royal Gala and Braeburn which have a variegated skin colour. The images included apples that rotated stem-over-calyx (as the starting position) and apples that rotated equatorially for all varietals. The variegated varietals had many more trackable skin features (1,731–2,065 image pairs) than the mono-coloured varietals (238–859 image pairs) and stem-over-calyx rotation produced more tracking image pairs (723–2,065 image pairs) than equatorial rotation (238–2,041 image pairs), because the stem and calyx provided trackable features. Probability histograms are presented for the normalized incremental rotation in pitch, roll and yaw for each varietal and each direction of initial rotation. Skew-Gaussian distributions are fitted to the probability data to give the mean, standard deviation, skew and mean square error for the pitch, roll and yaw for each of the four varietals in each of two initial orientations (stem-over-calyx and equatorial). These stochastic characterisations can be used in future Monte Carlo simulations to provide precise determination of camera coverage during the inspection of apples tumbling on rollers. This is an important contribution to the field of automated apple inspection.
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    Infrasound and low frequency noise guidelines: antiquated and irrelevant for protecting populations
    (The International Institute of Acoustics and Vibration, 11/07/2019) Alves-Pereira M; Krogh C; Bakker H; Summers S; Rapley B
    Over the past two decades, the increasing and unregulated production of infra- sound and low frequency noise (ILFN, ≤200 Hz) has led to a considerable rise in associated noise complaints and health-related issues. The most recent of such ILFN sources are industrial wind turbines (IWT). Acoustical field-data was collected within a home located in the vicinity of IWT, to which the AUC Rule 012 and its requirements were applied. In Ontario, IWT noise complaints were gathered under the Freedom of Information legislation. Goal: To explore the usefulness of current noise control rules when protecting human populations against ILFN generated by IWT.
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    Infrasound and Low Frequency Noise Guidelines: Antiquated And Irrelevant for Protecting Populations
    (The International Institute of Acoustics and Vibration, 1/01/2018) Alves Periera M; Krogh C; Bakker H; Summers S; Rapley B
    Over the past two decades, the increasing and unregulated production of infra- sound and low frequency noise (ILFN, ≤200 Hz) has led to a considerable rise in associated noise complaints and health-related issues. The most recent of such ILFN sources are industrial wind turbines (IWT). Acoustical field-data was collected within a home located in the vicinity of IWT, to which the AUC Rule 012 and its requirements were applied. In Ontario, IWT noise complaints were gathered under the Freedom of Information legislation. Goal: To explore the usefulness of current noise control rules when protecting human populations against ILFN generated by IWT.
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    Infrasound Exposure: High-Resolution Measurements Near Wind Power Plants
    (Intech Open, 2023-05-31) Bakker H; Alves-Periera M; Summers R; Mann R; Dickinson P; Suhanek, M; Summers, JK
    This chapter focuses on infrasonic (≤20 Hz) noise exposure as captured in and around homes located in the vicinity of wind power plants. Despite persistent noise complaints by local residents, no satisfactory acoustical event has yet been identified to justify this troublesome (worldwide) situation. Continuous (days), high-resolution recordings—spectral segmentation of 1/36 of an octave and 1-second temporal increments—have been acquired in many homes across the world revealing the presence of wind turbine acoustic signatures. These consist of trains of airborne pressure pulses, identified in the frequency domain as harmonic series with the fundamental frequency equal to that of the blade-pass frequency of the wind turbine. This report documents three such cases (Portugal and Scotland). The highest peaks of the wind turbine acoustic signature (up to 25 dB over background noise) occurred within the 0.5–5 Hz window which is classically defined as below the human hearing threshold; and yet these ‘inaudible’ phenomena appear to trigger severe biological reactions. Based on the prominence of the peaks in the harmonic series, a new measure is proposed for use in determining dose–response relationships for infrasonic exposures. This new methodology may be applicable to infrasonic exposures in both environmental and occupational settings.