Development of Nonwoven in Sound Absorption Technology

Rushikesh Digambar Patil
Department of Textiles (Textile Chemistry)
DKTE’S Textile and Engineering Institute, Ichalkaranji, India
Intern at Textile Learner
Email: [email protected]

Introduction:
Unwanted sound or noise is taken into account to be unpleasant and disturbing in many facets of life. Both within the office and in camera settings, this can be possible. Unwanted noise that interferes with a living creature’s metabolism is understood as sound pollution. The concepts of noise control were developed considerately for the acoustic environment. Loud noises appear to possess a negative impact on human physiological and psychological effects, which might end in irreversible disability, increased stress, decreased job productivity, disrupted sleep patterns, and communicative disruptions. This could be accomplished when the sound intensity is reduced to a grade that doesn’t hurt human hearing. The difficulty of pollution is worse in enclosed spaces. One method for creating comfortable surroundings is sound absorption. Fibrous and porous materials are recognized as essential components for sound absorption.

Noise pollution has been increasing in frequency and severity day by day. It’s a growing environmental problem that’s becoming a pervasive yet unnoticed style of pollution in both wealthy and underdeveloped countries. As disastrous because the effects of pollution are those of high noise levels, they have an adverse effect on both health and therefore the environment.

The World Health Organization (WHO) reports that noise-induced hearing disorder, which affects 120 million people worldwide, is the most prevalent and permanent job hazard. The EU Environment Agency also claims that pollution contributes to about 72,000 hospital admissions and 16,600 premature deaths annually in Europe.

The accepted standard unit for gauging sound loudness is that the decibel (dB). The WHO states that pollution occurs when noise levels exceed 65 dB. Noise is additionally harmful over 85 dB, and it’s agonizing at 120 dB. Low noise levels—below 65 dB during the day and, more critically, below 30 dB for sound sleep at night—are necessary to eliminate pollution.

High noise levels can have negative effects on both short-term and long-term health by raising systolic and diastolic blood pressures additionally as pulse rate. The WHO Community Noise Guidelines state that these health effects may successively cause social impairment, subpar productivity, diminished academic performance, and absence from the workplace and from school.

Each year, pollution causes 48,000 new cases of ischemic cardiopathy, chronic high annoyance in 22 million people, and chronic high sleep disturbance in 6.5 million people.

Approximately 90% of people’s time in metropolitan regions is spent indoors, in locations like their homes, offices, and community spaces. Thanks to expanded application areas, technological advancements, rising demand, and stricter noise limitation laws in many nations, the employment of acoustic textiles is significantly expanding globally. Urban growth, stricter building codes, growing environmental concerns, and sustainability are other factors driving the proliferation of acoustic applications.

The four categories of residential, commercial, automotive, and industrial are the first areas of noise reduction. In educational facilities, communal areas, entertainment venues, meeting or conference rooms, and buildings near highways or airports, acoustic solutions are essential.

Conference rooms, theaters, workspaces, and lecture halls are just some samples of enclosed areas which will generate, transmit, absorb, evaluate, and simulate sound. The reverberation time is the primary thought about determining a room’s acoustics (RT). On RT, there are differences within the amount of sound absorption and dispersion. Very high RT can raise the amplitude, which raises the likelihood of deafness.

Sound Absorption Characteristics:
A change in air, water, or another elastic medium’s pressure is what is referred to as sound, and the ear may detect this change as a stimulus for hearing. There are two components of sound: loudness and tone. Sound pressure in decibels (dB) is used to measure loudness, and hertz (Hz) is used to measure tone (Hz). Depending on the frequency and intensity of the sound, the human ear may or may not be able to hear it. The human ear is not sensitive to all sound frequencies. Humans can hear sounds at a frequency between 20 and 20,000 hertz (Hz).

The sound is produced as the substance or object vibrates. From the emitter to the receiver, these vibrations travel through a solid, liquid, or gaseous media in a waveform. A sound wave is thus the propagation of energy emitted by a source material or an item into a medium. The frequency, wavelength, and amplitude of a sound wave are taken into consideration. The characteristics of the waves can alter depending on how sound waves interact with the surface and the receiver’s item. From the surface, the sound wave can be transmitted, reflected, refracted, and diffracted.

Due to their fibrous structure and large total surface area, nonwoven materials are excellent sound insulation and sound absorption materials to reduce environmental noise pollution. Significant physical characteristics of nonwoven textiles for acoustic applications include areal density (mass), porosity, volumetric density, tortuosity, particle size distribution, and thickness. Some applications for nonwoven fabrics acting as noise absorption components include acoustic ceilings, noise-canceling comforters, and noise-proof barriers. Numerous studies have been conducted on the acoustic properties of nonwoven products, and a few of them are listed in the following sentences.

Sound Absorbing Materials:
Sound absorbers, diffusers, barriers, and isolators are some samples of noise-reducing devices. Sound-absorbing materials are the most topic of this study. By using sound absorbers, you’ll lessen the negative psychological and physical effects of loud noises while also reducing reverberation duration and force per unit area levels, improving speech clarity to create an area rather more attractive to the ear.

Most of the sound energy that hits materials that absorb sound is absorbed by such materials. High porosity materials are excellent choices because they need vacuum spaces where energy is also transferred and sound waves can go through the fabric effectively. So as to convert energy, sound must be absorbed. The sound’s Kinetic Energy is converted to thermal energy when it encounters the fiber. Textile structures comprise porous fibrous materials.

Why Nonwoven?
Due to its porous structure, nonwoven textile materials are now often employed in applications requiring sound insulation and absorption. These components serve as noise barriers, sound diffusers, sound absorbers, and sound reflectors. The sound wave needs to enter the absorbent material for sound transmission through friction. Different physical factors like fiber type, fiber diameter, material thickness, density, bonding process, air resistance, and porosity can affect how much sound energy is lost in textile materials. These necessary physical characteristics are provided by a broad inner surface formed by a flexible fiber skeleton of a fabric composition on the nonwoven surface.

Fibrous materials that are used for acoustic applications conjure woven textiles, knits, and nonwovens. Nonwovens are most often used because, because of their inherently porous character, they produce a superior range of materials. Non-woven fabrics’ main advantages include inexpensive costs, large manufacturing volume, flexibility in finishing options, and low areal mass density.

Recycling usage has increased as a result of environmental concerns. Bicomponent fibers and recycled polyester (PET) fibers are chosen for sustainability reasons. Through the utilization of carding, needle punching, and thermoforming techniques, PET fibers from used bottles were converted into non-woven materials. After disposal, they could be recycled another time through shredding, extrusion, or direct cutting into strips. By recycling everything from the raw ingredients to the finished product, this initiative adopts a sustainable approach. Utilizing recycled PET fibers has several advantages, which can be summed up as follows: lessening environmental pollution, preventing the depletion of petroleum supplies, lowering the value of nonwovens’ raw materials, and promoting the circular economy.

Through the mechanical web bonding process of needle-punching, the web’s fibers are mechanically bonded together after being randomly orientated through the dry-laid web manufacturing process of carding. After that, the needle-punched structure is thermoformed by melting bicomponent fibers to form it strong and robust. Needles produce an outsized number of pores on the surface, which efficiently allow sound waves to enter structures. The whole web generation and web bonding processes involve no chemical or water usage, leading to environmentally friendly production.

Investigation of the impact of aesthetic treatments on the acoustic performance of nonwoven materials happened because the project was being developed. All samples are 6 mm thick and have an areal density of 1,300 g/m². As an example, punch density, penetration depth, and stroke frequency are all tuned for needling.

It will be stated that there’s a direct correlation between extent coefficients and sound absorption coefficients, which explains how a material’s surface design impacts its acoustic properties. The following goals within the near future is summed up as follows: use of bio-based PET is promising in situ of recycled PET or both of them may well be combined in situ of virgin PET; polylactic acid, a bio-based and biodegradable polymer, PLA, will be used rather than bicomponent fibers for providing stiffness and mechanical stability; special cross-sectioned different fibers may be blended for a greater sound absorption coefficient; and multi layer sandwich structures could also be constructed by combining several web formation and bonding technologies in varieties of composite structures.

Conclusion:
Noise has become one amongst the main difficulties of everyday living, hurting our quality of life and, in some cases, our health, because the population has grown. As research into noise reduction continues, new ideas for systems which will absorb more of this irritating noise are being sought. Many diverse technical textile materials are manufactured within this area, which are intimately associated to the building construction, automobile, and mechanical industries. In terms of technological specifications, the adoption of those high-performance items is becoming more common. However, in today’s competitive market; products that may compete in terms of cost are favored. One amongst these favorite goods is recycled surfaces. Apart from the price advantage, waste materials are recycled into useable products, leading to completely environmentally friendly production that’s sustainable.

The features of ordinary polyester and polypropylene nonwoven insulation materials routinely utilized in the market, yet as nonwoven textiles made of recycled materials, were compared during this study. When the test results were analyzed, it had been determined that recycled materials utilized in sound insulation had a really successful competitive performance compared to traditional materials. They need the qualifications to fulfill the expectations in terms of sound insulation when manufactured in sufficient thickness. In situations where sound insulation is desirable (such as children’s homes, hospitals, entertainment venues, and therefore the automotive industry), in addition as within the field of applied science, insulation materials are utilized.

The supply of a sustainable world, the development of an environmentally friendly approach, and also the technical evaluation of waste materials are additional useful applications for recycled materials. By 2019, 100% PES and r-PET fibers will cost about 1.6 $/kg, 3.2 $/kg, and rm-PES fibers will cost about 1.2$/kg. The worth of PP fiber are approximately 3.2 $/kg. Recycling materials will likely offer a major advantage to both producers and consumers from an economic perspective.

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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.

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