Dissertation: Noise levels in corridors can be controlled by appropriate measures

Juhani Kuronen, Lic. Sc. (Tech.), has developed a simplified algorithm for controlling noise in echoing corridors for his thesis at Lappeenranta University of Technology.  Using this algorithm, builders can quickly and easily estimate the type and volume of dampening materials required to achieve the desired end results.

"Alterations made at a later date are labour-intensive and expensive, especially at renovation sites and in finished buildings.  This is why the benefit-cost ratio of acoustic materials used to line corridors should also be optimised", Kuronen says.

We are all well familiar with echoing corridors in hospitals, schools, offices and public transport waiting rooms, as Kuronen finds that not enough attention is paid as yet to corridor noise in design and construction.

"In long and narrow waiting rooms, PA announcements become muffled and are impossible to make out. This is a serious problem in case of accidents and emergencies, as people may mishear instructions communicated in the announcements. "

"Studies indicate that loud noise carried from corridors into the classroom at schools is the greatest cause that makes speech difficult to understand", Kuronen illustrates the extent of the problem.

Excessive use of acoustic materials is not the optimal solution

The disruptive qualities of corridor noise can be combated by working on noise sources, improving sound insulation in structures and adding dampening materials to the corridor and working areas.

"Excessive use of dampening material is expensive and also makes a room echoless, or acoustically 'dead'. Lack of echoes does not usually make speech more readily understandable. On the contrary, noise from the corridor becomes even more audible in a dampened classroom, as the background noise levels of the classroom itself are lower", Kuronen explains.

There is a great difference between the level of echoes in a corridor when acoustic dampening is or is not used. As part of his research, Kuronen studied changes in the noise levels of a single corridor while the university buildings were being renovated.

"The removal of mineral wool from the corridor ceiling increased the noise level by 11 dBs. This is a dramatic increase. When the noise level goes up by ten decibels, we experience it as the noise having doubled.  At a later date, dampening elements were added in the ceiling structures of this corridor, which helped to decrease the noise to considerably more pleasant levels."

Commercial modelling programs good but cumbersome

According to Kuronen, a simple algorithm for estimating the volume of dampening material needed was already available for normal living accommodation, but it was completely unsuitable for tunnel-like corridors.

Kuronen explains that while the latest acoustic modelling programs are versatile and efficient, specialist skills are needed to use them, and they are more suitable for acoustic research than as tools for engineers and designers.

"In minor building projects and short-term noise-abatement measures, these modelling tools have often been found too cumbersome, which restricts their application even if they are useful."

Kuronen's study introduces a calculation method based on the mirror image theory in geometrical acoustics, which makes it possible to quickly compare various solutions for acoustic dampening in rooms. In order to use this algorithm, the builder must know the width, height and length of the corridor, as well as the surface materials, the sound absorption capacity of which can be found in manuals or manufacturers' brochures. The calculation can be performed using a pocket calculator or spreadsheet software.

Juhani Kuronen Lic. Sc. (Tech.) will defend his doctoral dissertation Continuous Sound Power Distribution Algorithm for Modelling Noise Levels in Long Corridors in the field of industrial engineering and management at Lappeenranta University of Technology on 16 August at 12 noon in room 1382. Docent Rauno Pääkkönen, D. Sc. (Tech.), from the Finnish Institute of Occupational Health, Tampere, and Docent Esko Toppila, Ph. D., from the Finnish Institute of Occupational Health, Helsinki, will be the opponents. Docent Heikki Laitinen, D. Sc. (Tech.), from Lappeenranta University of Technology will be the custos.

Over thirty years of experience in noise abatement

Kuronen completed his doctoral dissertation just in time before his retirement. Kuronen has been teaching noise abatement at the university as part of corporate security and safety and security management. Kuronen joined the university in 1990, before which he had worked with noise abatement issues at the Finnish Institute of Occupational Health for some ten years. He has found his long career as a university teacher pleasant and rewarding.

Lappeenranta University of Technology does not have a research team on acoustics and noise abatement, and Kuronen has thus been the sole representative of his field at the university. In particular, Kuronen has worked together with researchers in the fields of industrial engineering and management, mechanical engineering and energy technology.

Kuronen would like to see the education of professionals in the building sector at various educational institutions contain more studies in acoustics. In his experience, there is a need for this knowledge. Kuronen finds that awareness of the impacts of noise remains low in many sectors: while noise abatement is discussed in the industrial sector and ear protection is used, people often are careless with the protective equipment.

THE DOCTORAL CANDIDATE'S PERSONAL INFORMATION:

Name: Juhani Kuronen
Year and place of birth: 1948 Ruokolahti
Home municipality: Taipalsaari
Education: Matriculation examination at Vuoksenniskan yhteiskoulu 1969
Structural engineer, Lappeenranta University of Technology 1975
M. Sc. (Tech.), Lappeenranta University of Technology 1981, Lic. Sc. (Tech.) 1998
Employment: University teacher, Lappeenranta University of Technology

More information:
Juhani Kuronen, 040 7182 536, juhani.kuronen@live.fi , juhani.kuronen@lut.fi