Rating the impact sound insulation of concrete floors with single-number quantities based on a psychoacoustic experiment

Impact sounds are different living sounds directed at floors in dwellings. Objective single-number quantities used in rating the impact sound insulation of floors and between dwellings have been presented in standard ISO 717-2 (2013). It has long been recognised that the standardised single-number quantities do not correlate well with the subjective judgement of living impact sounds. The main objective of this thesis was to develop new single-number quantities that would correspond better with the subjective experience of living impact sounds transmitted from the neighbouring dwelling upstairs.
New single-number quantities concern five different living impact sounds. In
addition, the purpose was to develop a single-number quantity that explains the
annoyance caused by all five impact living sounds. Experimental data for the
development of the new single-number quantities was produced by measuring the impact sound insulation of concrete floors with a wide scale of floor coverings. Five spectrally different living impact sounds were also measured and recorded. These sounds were walking with socks, hard and soft shoes, super ball bouncing and chair moving. A psychoacoustic experiment with an extensive number of participants was conducted to find out the loudness and annoyance of the living impact sounds and, furthermore, the associations between the subjective judgement of the sounds and objective single-number quantities. The experimental data of the impact sound insulation measurements and the psychoacoustic experiment was utilised in mathematical optimisation of new single-number quantities. As a starting point for the formulation of the new single-number quantities, it was required for them to be able to be expressed as the sum of the present single-number quantity L’n,w or L’nT,w and a new spectrum adaptation term instead of CI or CI,50-2500. An optimised reference spectrum could be developed for each of the five sound types, each leading to a better correlation between the subjective judgement of the annoyance of the sounds and the single-number quantities than can be achieved by using any of the single-number quantities presented in the standard ISO 717-2. In addition, an optimised reference spectrum was derived which explained the annoyance of all five sound types reasonably well (coefficient of determination R2 = 0.93) and better than any of the standardised single number quantities (e.g. R2 = 0.86 for L’n,w + CI,50-2500). Another objective of the thesis was to study the measurement uncertainties of various single-number quantities for rating the impact sound insulation at a frequency range of 50 Hz and above. It was shown that the measurement uncertainty of a single-number quantity depends on the impact sound spectrum of the floor type. The results also indicate that the uncertainty depends on the extent that the single-number quantity weights the low frequencies. The measurement uncertainty at a low frequency range, however, does not become so large that it would prevent developing new reference curves that weight this frequency range more strictly than
the present, standardised reference curves starting at 100 Hz.