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Noise Pollution
Published in Subhash Verma, Varinder S. Kanwar, Siby John, Environmental Engineering, 2022
Subhash Verma, Varinder S. Kanwar, Siby John
Sound in the atmosphere travels uniformly in all directions, radiating out from its source. The sound intensity is reduced as the square of the distance away from the source of the sound, according to the inverse square law. As a sound wave travels from a point source, it spreads around in concentric spheres. Since the surface area of a sphere is proportional to its radius squared, sound intensity decreases proportionally to the distance squared. In other words, doubling the distance will cause the sound intensity to decrease four times. That is, the SPL is proportional to 1/r2, where r is the radial distance from the point source. An approximate relationship can be developed if the sound power is expressed as a logarithmic ratio based on some standard reference power, such that: Pointsource,SPLr=SPL0−20logr
Standards in Architectural and Building Acoustics
Published in Waldemar Karwowski, Anna Szopa, Marcelo M. Soares, Handbook of Standards and Guidelines in Human Factors and Ergonomics, 2021
Joanna Jablonska, Elzbieta Trocka-Leszczynska
There are several basic issues connected directly toward a description of sound, and important for this elaboration is sound intensity level—which is logarithmic and retains a reference value. It is dependent on the relation between the certain differences in sound pressure, called sound pressure level, and is described in decibels dB. The range of sound intensity level is measured between a threshold of hearing of 0 dB and 130 dB—the so-called threshold of pain. This parameter has logarithmic and reference character; thus, they are not heard by humans in a linear manner but based on the frequency of acoustic wave—expressed in hertz (Hz). Therefore, in acoustics, a correction according to “A” hearing curve is used to gain positive values that are as objective as possible that compare and manage this complex phenomenon. Moreover, the sound level can be measured in different ways due to varied outcomes required—for example, measurements used for industry in the USA are performed according to the sound measurement weighting networks “A” and then are expressed in dBA, need for evaluation of human risk or with special attention toward low frequencies (Driscoll, OSHA technical manual; Wroclaw Spatial Information System, 2017).
Sound Levels
Published in Fang Zhu, Baitun Yang, Power Transformer Design Practices, 2021
Sound power is the rate at which energy is radiated (energy per unit time). Sound intensity is the rate of energy at a point, that is, through a unit area. Sound intensity is a vector quantity. Sound pressure is a scalar equivalent quantity having only magnitude. Normal microphones are capable only of measuring sound pressure, this is sufficient for majority of transformer sound measurement situations.
Analysis and optimisation of the cutting parameters based on machinability factors in turning AISI 4140 steel
Published in Canadian Metallurgical Quarterly, 2022
Mustafa Özdemir, Abidin Şahinoğlu, Mohammad Rafighi, Volkan Yilmaz
Sound intensity gives information about many machining conditions. The most important one is an indication of increased current value or cutting force value. With increasing tool wear, cutting forces and current values increase. Therefore, as the tool wear increases, the sound intensity also increases. This variation in sound intensity has wide use in industrial applications. The change in sound intensity is similar to cutting forces. Based on Figure 8, the sound intensity decreased with increasing cutting speed, the sound intensity increased with increasing feed rate and cutting depth. This result is well fitted with the literature [23, 32].
A proposed technique for power extraction from acoustic energy scavenging
Published in International Journal of Electronics, 2018
Kyrillos K. Selim, Ayman Haggag, Fathy Z. Amer, Wael A. Rady, Ahmed M. El-Garhy
From Table 1, we can describe each parameter as follows: Noise Source: a source that produces sound waves have certain values of sound intensity levels and frequencies.Sound Wave Frequency is the number of full cycles of a sound wave per second. The sound frequency value is varied according to the noise source.Sound Intensity Level: it is defined as the power carried by sound waves per unit area; it is measured by the decibel unit.Piezoelectric Transducer Classification: the piezoelectric transducer is classified according to dimensions (it is varied in mm), shape (circular, plate, cylinder, ring, or disk), material (ceramic, polymer, or composites), and application (sensor, generator, or actuator).The Resonant Frequency of the Piezoelectric Transducer: it means the frequency domain of operating the piezoelectric transducer.Piezoelectric Transducer Connection Methods: the way of connecting transducers together.Mounting Methods of Piezoelectric Transducers: how to mount transducers in an appropriate position with respect to the noise source.The Electrical Circuit extracts the converted power from acoustic energy.Impedance Matching is the matching between the circuit impedance and load resistance.