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Psychoacoustical analysis, models and recommendations for noise from computer systems
2002 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The increasing use of computers has made the acoustical noise from system units an important part of our working environment. Despite that this kind of noise does not constitute a risk of hearing damage, it can cause other problems such as mental tiredness, reduced performance and reduced working satisfaction. Research on how noise influences our health is therefore very important in order to minimise potential damage and risks. To transform the hearing sensation into numerical values psychoacoustical parameters or descriptors has been developed, that are based on models of our hearing. In this work, the noise has been separated into five aspects for analysis, namely level of noise, impulsiveness, relative amount of high frequencies, modulation, and presence of tones. There exist a large number of parameters for describing these aspects of a sound. The aim of this work was to determine which parameter or combination of parameters that are most suitable to use, when estimating influence of acoustical noise from a computer. These parameters or parameter are then to be used in a recommendation regarding the highest allowed levels of noise from system units. A psychoacoustic experiment was conducted with 20 test persons to investigate the correlation between how different noises are perceived and the tested parameters. In the experiment, office-working conditions was simulated with the test persons solving tasks on a computer. While solving the tasks 25 recorded and digitally manipulated computer noises were reproduced to judge by the test persons. A computer program was developed that automated the arising of tasks, reproduction of noises and the subjective answers from the test persons regarding the noise. An additional computer program was developed to determine the psycho- acoustical parameters from the recorded sound pressure. The program includes new algorithms for tone detection, balance point and modulation. Statistical analysis of the data from the experiment resulted in three regression models that included the parameters Loudness Zwicker, Balance point, modified Fluctuation Strength, Level of tone and Impulsiveness A- weighted. Low correlation was found between the annoyance response and the most widely used parameter for measurement of noise, A-weighted sound pressure level. This parameter was however not rejected because of the fact that it is well known, widely used and relative easy to measure. Four different models of recommendations regarding noise from system units are suggested with the number of parameters varying from one to five. A model may be selected according to the level of sophistication desired in the analysis. The work also includes a study of the noise emitted from 5 typical system units of Personal Computers (PC). Further suggestions for measurement procedures are made for cases where the directivity of the noise is of importance.

Place, publisher, year, edition, pages
Keyword [en]
Technology, acoustical noise, psychoacoustics, psychoacoustic, experiments, Loudness, impulsiveness, presence of tones
Keyword [sv]
URN: urn:nbn:se:ltu:diva-54508ISRN: LTU-EX--02/370--SELocal ID: b75733c4-849f-4cb1-9c04-31463d292fcdOAI: diva2:1027889
Subject / course
Student thesis, at least 30 credits
Educational program
Engineering Physics, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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