The history of noise control engineering

1.and noise.

**It is a regular and pleasant sound, which can make people happy and excited.

Noise is an irritating sound that affects people's normal work, study and rest.

2.Noise hazards.

In addition to disturbing people's rest and sleep, reducing the efficiency of work and study, strong noise can also cause ear discomfort.

Such as: tinnitus, earache, hearing damage, etc., causing neurasthenia, cardiovascular diseases, and even nervous system disorders, mental disorders, endocrine disorders, etc.

3.How to control noise.

Start with the source of the sound: such as prohibiting the horn, equipping the sound enclosure, etc.

Start with the transmission route: like sound-absorbing walls, soundproof walls, etc.

Start with the human ear: like earbuds, earmuffs, etc.

The harm of noise can not only cause hearing loss and memory loss in normal people, but also cause myocardial ischemia and indigestion. For patients, it can aggravate the disease, so the effective comprehensive management of the voice should attract people's attention.

The presence of noise interferes with voice communication and makes communication worse effective. Especially in the context of strong noise, the voice signal is even completely overwhelmed by the background noise and is almost unrecognizable. The communication process cannot be realized normally, which has a serious impact on production, daily life, and military operations, and causes huge economic losses to individuals, units, and even the country.

Therefore, in the context of strong noise, how to effectively suppress and eliminate interference noise has become a hot topic in people's research. In order to solve the problem of noise cancellation in voice communication in the background environment of time-varying strong noise, the existing denoising methods were compared and analyzed, and finally the adaptive noise cancellation was selected, and the feasibility of adaptive noise cancellation was analyzed and demonstrated. Then, the filter structure is compared and analyzed, the performance of the Minimum Mean Square Error (LMS) algorithm and the Recursive Least Squares (RLS) algorithm is compared, and finally the system model is constructed by using the finite impulse response (FIR) transverse filter structure and the recursive least squares (RLS) algorithm to determine the adaptive noise cancellation scheme.

This paper focuses on the research of adaptive filtering algorithms. On the basis of the in-depth analysis of the standard Recursive Least Squares (RLS) algorithm, an improvement scheme is proposed to solve its inherent shortcomings. Then, three improved algorithms that have been successfully applied to adaptive equalization and adaptive estimation are introduced, and the principle analysis and performance verification are carried out.

In recent years, more than 10 highway and railway sound barriers have been built in China, including sound barriers of different forms, materials and structures. He has accumulated certain experience in the design, manufacture and installation of sound barriers. China is about to issue a code for the design of sound barriers to guide the design and installation of sound barriers.

China has issued more than 10 standards for measurement methods and evaluation of noise control equipment, although it is not perfect. The national environmental protection department has initially established a quality inspection agency for noise control equipment. A small number of noise control equipment has technical conditions and quality assurance systems.

Some noise control equipment manufacturers have obtained ISO9000 and ISO14000 certification. Some noise control devices are also recognized by the international market.

However, it should also be noted that there is still a big gap between China's noise control equipment and its industry and the international advanced level. The main gaps are as follows:

There are too many duplicate products at the same level or at a low level, there is little technological progress in materials, structures and processes, and few products with high technical content;

backward process equipment, lack of special production equipment, and lack of large-scale production capacity;

Lack of quality testing instruments and equipment for noise control equipment.

Your topic is outrageous! 200dB(a) blowers are not available now and will not be in the future! Mufflers with only a ventilation area have no practical value.

In the face of noise pollution, which is increasingly threatening the living environment of human beings, the seven major technologies of noise control, such as sound absorption, sound elimination, sound insulation, vibration isolation, damping, personal protection, and building layout, have been significantly developed. The internationally mature sound insulation theory and practice in the field of building acoustics, such as the law of sound insulation quality and a series of empirical formulas, naturally become the basis of sound insulation technology. In China, the Institute of Building Physics of the Chinese Academy of Building Research conducted a comprehensive analysis of various domestic sound insulation components, and a summary table of transmission losses of domestic sound insulation components was obtained.

Tsinghua University has carried out experimental research on lightweight structures such as gypsum board, and the relationship between the number of layers, the thickness of the air layer, the type of keel, the filler and the amount of sound insulation. Point out ways to improve the sound insulation performance of gypsum board. The Institute of Acoustics of Tongji University conducted a survey on the sound insulation components of nearly 1,000 households in Shanghai, and proposed a quasi-double-layer wall with a single-layer composite structure.

A solution that can increase the amount of sound insulation while reducing the weight by a third. The Institute of Physics of the Institute of Construction and Research and the Tenth Institute of the Ministry of Electronics have carried out in-depth research on the sound insulation door and compiled a standard atlas of sound insulation doors. Beijing Institute of Labor Protection, Institute of Acoustics of the Academy of Sciences, Shanghai Jiao Tong University Noise, Vibration and Impact Research Laboratory, Shanghai Institute of Industry, Ninth Institute of China Shipbuilding Corporation, Shanghai Mechanical and Electrical Design Institute, Tsinghua University, Shanghai Labor Insurance Institute, etc., have successfully developed sound insulation covers or sound insulation rooms for air compressors, motors, ball mills, refrigerations, gas turbines, various fans, jade grinding machines, nail making machines, and chainsaw string machines in industrial noise.

Noise control engineering is an emerging scientific and technological field at the intersection of physics, acoustics, mechanical engineering, architectural engineering, materials science, chemical engineering, computer, mathematics, physiology, and psychology. This discipline not only has theory, but also engineering design, product design, and has truly become an integral part of the engineering discipline.

In vibration isolators and damping materials, personal protective equipment, such as earplugs, earmuffs, acoustic cotton, etc., have formed commercial products in Europe, the United States, and China. In terms of acoustic measuring instruments, the products of Denmark BK Company and Japan Liwen Company have become powerful tools for noise measurement. China's acoustic instruments have established their own production plants from scratch, and introduced production lines and production technologies from Japan to improve product quality.

During this period, Cheng Mingkun and Liu Ke carried out research work in the field of environmental acoustics, Wang Jiqing in urban building acoustics, and Zhang Shaodong and others also carried out very meaningful work in acoustic measuring instruments. In the face of increasing noise pollution, ISO and some developed countries have developed and promulgated a series of noise standards.

Noise Control Techniques (2nd Edition) is divided into 9 chapters, with Chapter 1 being an introduction, focusing on noise pollution and hazards; Chapter 2 is the foundation of acoustics, which is the basis for learning the following chapters; Chapter 1 is Noise Measurement and Noise Evaluation; Chapter 5 is an introduction to noise control; Chapters 6 to 9 are part of noise control technology, which describes the principles and practical techniques of sound absorption, sound insulation, sound reduction, damping and vibration isolation, and field engineering examples are attached to each chapter. "Noise Control Technology (2nd Edition)" can be used as a textbook for environmental engineering, environmental management and environmental related majors in colleges and technical colleges, as well as a training material for in-service environmental protection personnel and a reference book for technical personnel in related fields.