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Noise and light pollution
Published in Abhishek Tiwary, Ian Williams, Air Pollution, 2018
Sound surrounds us daily and it would be difficult to live without it. Sound is a vibration that usually propagates as an audible mechanical wave of pressure and displacement through a medium such as air or water. Noise is defined as unwanted sound, which can cause irritation and stress. Noise is subjective, and different people react to it in different ways. What can cause annoyance to some people may be barely noticeable by others. It can interfere with normal activities such as sleeping or conversation, or even disrupt or diminish the quality of life. In extreme conditions, noise can cause physical damage to those affected. Noise pollution has received little attention compared to other types of pollution, such as air or water pollution. This is probably because it is not possible to see, taste or smell noise.
General Princlpes
Published in Martin B., S.Z., of Industrial Hygiene, 2018
Sound waves are defined by their frequency, wavelength, and velocity. The frequency of a sound wave is the number of times per second that a vibrating body traces one complete cycle. It is measured in Hertz (Hz). Frequency is frequently thought of as pitch. Humans can hear sounds in the range of 20 Hz to 20,000 Hz. The distance a wave travels in one cycle is called its wavelength. Wavelength is measured in feet or meters and is expressed by the letter lambda (λ). Velocity, called the speed of sound, can be calculated using the following formula: () c=fλ
Basics of Resonance
Published in Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha, Optical Sensors for Biomedical Diagnostics and Environmental Monitoring, 2017
Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha
Acoustic resonance phenomenon in an acoustic system that amplifies the sound whose frequency matches with one of the natural frequencies of the system is termed as resonant frequency. Usually, there exist several resonant frequencies for an acoustic system. The change in mass, conductivity, elasticity, and the dielectric properties of the resonant system changes the values of resonant frequencies. This property supports the sensing application using acoustic waves. The acoustic waves generated at the surface of the system are termed as surface acoustic waves, while if these are produced in the bulk of the system then they are called as bulk acoustic waves. In the case of optical sensors, coupling of SP waves and surface acoustic waves is used (Friedt and Francis 2016). For example, in biosensing applications using this configuration, the binding of analyte molecules with the active sites present at the recognition medium causes change in the optical and mechanical properties of the sensing unit. The change in the optical properties is detected by SPR by observing the shift in resonance wavelength/angle in the output spectra, while the change in mechanical properties is detected by observing the change in resonant frequency. Thus, by combining both the phenomena, a highly sensitive sensor can be achieved as it evaluates the actual binding of analytes with the recognition sites.
Textile dye effluent treatment using advanced sono-electrocoagulation techniques: A Taguchi and particle swarm optimization modeling approach
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Numerous technologies reported for treating textile wastewater-like coagulation, flocculation, adsorption, membrane filtration, biological methods, advanced oxidation, and reduction process, etc. (Singh et al. 2019). Electrochemical wastewater technologies such as electrocoagulation, electro-oxidation, and electro-flotation are efficient wastewater technologies which do not require any chemicals. The electrocoagulation techniques have several advantages over the traditional coagulation process such as smaller operation time, maximum removal efficiency, minimum sludge generation, and compatibility (Safwat 2020). Sound is mechanical energy that can travel through solid, liquid, and gas media. In sonication, ultrasound wave with a frequency of 20,000 Hz or higher is applied. Depending on the insolation power and frequency, ultrasound generates localized high-energy molecules in a medium (Maha Lakshmi and Sivashanmugam 2013). When the negative pressure is strong enough to disrupt the distance between the molecules of a liquid, cavitation bubbles form (Dizge et al. 2018). Sono-electrochemistry has several advantages, including the ability to reduce the thickness of the diffusion layer, clean the electrodes, and accelerate the adsorption process (Yang et al. 2016).
The automated driver as a new road user
Published in Transport Reviews, 2021
Ane Dalsnes Storsæter, Kelly Pitera, Edward D. McCormack
Auditory feedback in vehicles provides information on the engine, transmission, tyres and aerodynamics (Walker et al., 2006) as well as warnings of disruptive events such as the proximity of emergency vehicles (Macadam, 2003). Whether a sound is audible to humans depends both on the power of the sound, measured in decibels (dB), and the frequency of the vibration (Hz). Humans hear above 0 dB and feel discomfort from 110 dB and up (Institute for Quality and Efficiency in Health, 2008). Normal hearing detects frequencies of sound between 20 and 20,000 Hz (Bagai, 2006). Humans are excellent at localising the sources of sounds, i.e. determining the range, elevation and azimuth angles of a sound’s source (Duraiswami & Raykar, 2005). Hearing is also used to determine the movement of objects that are not immediately in view, and it is therefore vital for safe and effective orientation (Gatehouse & Noble, 2004). The distance range of hearing is dependent on the loudness of the sound (Pasnau, 1999) as well as environmental factors including temperature and humidity (Harris, 1966).
Dispenser-printed sound-emitting fabrics for applications in the creative fashion and smart architecture industry
Published in The Journal of The Textile Institute, 2019
Yi Li, Russel Torah, Yang Wei, Neil Grabham, John Tudor
Eight speakers were tested in this work: 6 different sized dispenser-printed speakers and 2 commercial conventional speakers for comparison, one being an Apple iPhone 6 handset speaker and the other a Logitech H390 headset speaker. These two speakers are chosen because they are widely used indoor state of the art sound-emitting devices. A background noise measurement is also made as a reference. Figure 9 shows the frequency response of the printed fabric spiral speakers for a sine sweep from 20 Hz to 20 kHz over a 20 s period. The same magnet is used on top of each different fabric speaker. The sound output level is measured in decibels (dB) relative to a reference sound pressure in air of 2 × 10−5 Pa, with the maximum sound level using ‘Z’ frequency and fast time weighting. The background noise of the test environment is shown in Figure 10 with two tests being performed to quantify random variations. Comparing Figures 9 and 10, the frequency response of the printed fabric speakers covers the full band of frequency range from 20 Hz to 20 kHz, as it can be seen that the sound emission from the fabrics is greater than the background noise frequency response plot throughout the range from 20 Hz to 20 kHz. The sound output level measurement shows that between 250 Hz and 5 kHz frequency range, the sound output level is above 70 dB, which is a significant sound emission and comparable to a normal speech at 1 m in an indoor environment (Portland International Jetport Noise Exposure Map, 2004).