Study on the possibilities to apply spectrumindex

Juhani Parmanen, Pauli Sysiö

Research output: Book/ReportReport


Possibilities to apply spectrumindex in building acoustics are studied. As usually, spectrumindex refers to the difference of two sound pressure levels caused by the same sound field and measured using two separate frequency weightings (A- and C-weighting). The purpose of the study is to develope a simple method in which one can apply the spectrumindex to evaluate the traffic noise reduction indices existing already in a NORDTEST-method. Some difficulties in that method, i.e. its definitions, used spectra and the extensive datamaterial, are discussed too. Further, the spectrumindex principle has been applied to a testmaterial of 20 different windows. Two alternatives have been used as basic sound reduction indices, one for pink noise and the other for a traffic noise spectrum modified from the spectrum given in the French standard NF S 31-051. Three different equations were tested in estimating the reduction index for other spectra for which only the spectrumindex is known. Finally, the equation including the best realizable sound insulation curves has been chosen as the most feasible estimation method. It has been shown, that by accepting some little limitations concerning the noise spectra and magnitude of spectrumindex, one can get very reliable estimation results. In general, the deviation will be at the most 1 dB from the correct value calculated in accordance with the NORDTEST-method. This may be seen important also therefore, that instead of the 32 different numbers needed traditionally, here only three are necessary in calculating the noise reduction index. The study has been finalized by using a Greek material consisting of 11 exterior doors and one single pane window.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages42
ISBN (Print)951-38-4227-4
Publication statusPublished - 1992
MoE publication typeNot Eligible

Publication series

SeriesVTT Publications


  • buildings
  • acoustics
  • sound waves
  • noise reduction
  • acoustic measurement
  • estimating
  • utilization
  • sound pressure
  • calculations
  • methods
  • spectra
  • indexes (ratios)
  • windows
  • doors
  • evaluation
  • Spectrumindex


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