Acoustics involves many areas. Knowledge in acoustics is important for many professional engineers and architects, but also for professionals from other faculties, such as medical doctors, psychologists, biologists, oceanographers, media professionals and so forth. The figure bellow is an attempt to illustrate the area from the core ‘fundamental physical acoustics’ to its applications and relations to a range of disciplines.
Knowledge in acoustics is essential to promote the creation of environments, both indoors and outdoors, involving rooms with good listening conditions for speakers, musicians and listeners and also living environments and working areas which are reasonably free from harmful and/or intruding noise and vibrations and with acoustic comfort. In other words; acoustics is a discipline of great importance for a sustainable development.
Courses given by the department of Applied Acoustics at Chalmers cover important parts of the areas sound and vibration, promoting the positive effects of sound – an important part of life – and abating the negative effects of sound. Within this area we have courses in audio technology, electro-acoustics, active control of sound and courses in theoretical acoustics. The courses are designed for students with different background, (e.g. civil engineering mechanical engineering, physics or electrical engineering).
Smoke and noise were the classical symbols for industrial progress and power in the 19th and 20th centuries. The smoke is to a great extent eliminated, but the noise remains. Noise is a difficult pollution, both in indoor and outdoor environments. The fundamental reason for noise is that we depend in our society on so many different machines and tools and most of them are quite too noisy. This is true for aircraft, road vehicles, ventilation systems in buildings, outboard engines, lawn mowers, household machines, industrial machines and tools, etc. To make these machines and tools quieter and free of vibrations is mainly a task for the mechanical engineer. It is a demanding task. It is much easier to make a machine or a car that runs faster than to make it quieter. The tasks related to acoustics also involve comfort and what we call sound quality. The product must have the right sound to satisfy the customer! This has become increasingly important especially for cars. Therefore, acoustics and noise control is a very important work area in the automotive industry and knowledge in acoustics needs to be an integrated part of mechanical engineering.
It is often said that the most effective method to solve environmental problems is the stop the pollution at the source. If we then take the present day situation it is a very long way to go until all machines and tools are so quiet that their noise pollution will not cause any problem in their environments. To give a rough figure, it would demand a noise reduction of each individual source of the order of 10 – 30 dB if all the problems were to be solved solely by reduction at the source. This is out of reach in a foreseeable future with available technology (and knowledge).
To what extent people are exposed to noise is, however, not only determined by the emission from the machinery but also how the built environment is formed. Acceptable or good environments can be obtained through adequate design of city plans, building plans and constructions. It is an important task for engineers to solve the problems caused by noise emission from machines and tools, so that people when they work, rest at home, walk in the cities, go to the cinema or theatre, etc. encounter a good acoustic environment. Closely related to this is also the design of buildings with adequate sound insulation between different activities.
Sound is an important part of human life and culture. In class rooms, meeting rooms, cinemas, theatres, concert halls, etc. the design has to be such that it is easy to speak and comfortable to listen with a high degree of intelligibility. Also these parts of acoustics belong to the professional area of a specialist in sound and vibration.
The master’s programme “Sound and Vibration” has the task to prepare you as and engineer for these tasks.
Noise is a severe pollution of great extend
High noise levels can cause hearing impairment. This is a severe problem in industrial workplaces where much progress has been made but not sufficient. Still thousands of workers are exposed to levels, which will damage their hearing. In many cases new industries in e.g. Sweden have been designed for substantially lower noise levels. This is reasonable since the risk for hearing impairment is far from negligible at 85 dB.
Noise is also a major environmental problem. Traffic is the dominating community noise source. A larger portion of a country’s population is exposed to road traffic noise than to noise from aircraft or rail. There are also other important noise sources such as noise from neighbours (e.g., lawn mowers) and building installations (e.g., air conditioning equipment) which typically are easier to control than traffic noise. Nevertheless, such sources often destroy acoustic environments that otherwise could have been quiet and relaxing, such as backyards, gardens, parks, etc. Most people are typically exposed to several noise sources. In contrast to many other environmental problems, noise pollution is still growing. Moreover, noise is the only environmental impact for which the publicåÕs complaints have increased since 1992. The development is unsustainable.
Noise affects human health and well being in several ways. A Task Force of the World Health Organisation has identified the following specific health effects: interference with communication, noise-induced hearing loss, annoyance responses, and effects on sleep, cardiovascular and psycho-physiological systems, performance, productivity, and social behaviour. Various combinations of these effects are considered critical for specific environments such as dwellings, schools, hospitals, concert halls, outdoor concerts and discotheques as well as for sensitive time periods (night- and daytime, weekends). In selecting guideline values for specific environments based on specific effects, vulnerable groups are particularly considered, for example, persons with hearing deficits, shift workers, the elderly, infants and young.
The term sustainable development was established by the Brundtland commission and brought further in the Rio conference resulting in Agenda 21. What does a sustainable development imply in terms of noise. Reasonable requirements are the following.
- Noise which gives rise to noise induced hearing impairment is unacceptable
- Noise, which deteriorates the quality of life by causing sleep disturbance, speech interference and/or severe annoyance, is unacceptable.
- Noise which interferes with speech communication, learning and teaching in a society built on knowledge is unacceptable.
These demands together imply that almost each tool or machine is 10 – 30 dB too noisy to fit into a sustainable development. Sound insulation between dwellings ought to be approximately 10 dB higher than today’s minimum requirements to give the occupants sufficient protection.
To decrease noise emission by 10 dB means to remove 9/10 of the sound power. 20 dB means that 99/100 must be removed and 30 dB that 999/1000 of the sound power must be eliminated.
A sustainable development also involves technology with a minimum of energy and material consumption, e.g. primarily lightweight constructions of recyclable material in buildings, machines and vehicles.
It is a complicating factor in achieving the goal of a sustainable development that increased weight is the most straightforward method to obtain better sound insulation in buildings and less noise from machinery. It is a real challenge for skilled engineers to fulfill these requirements for a sustainable development in terms of noise.