This study investigated the effect of a spatial factor, the magnitude of interaural cross-correlation ͑IACC͒ function, on subjective responses to heavy-weight floor impact sounds. Heavy-weight impact sounds were generated by a heavy/soft impact source ͑impact ball͒ in real apartments, so that impact sound pressure levels ͑SPLs͒ ͑L Amax ͒ and IACC could be analyzed. Just noticeable differences ͑JNDs͒ of impact SPL and IACC were investigated through the use of impact ball sounds. JNDs were determined by the criteria of 75% correct answers by participants, and it was found that JNDs of impact SPL and IACC were around 1.5 dB and 0.12-0.13, respectively. In addition, the annoyance caused by an impact ball was evaluated by changes in these two parameters. The results show that annoyance increased with increasing impact SPL and with decreasing IACC; the contributions of the two parameters to the scale value of annoyance were 79.3% and 20.4%, respectively. This indicates that the effects of IACC should be considered for the evaluation of annoyance, and the subjective response to impact ball sounds can be improved by controlling IACC, as well as impact SPL.
This study investigates the effect of temporal decay on perception of heavy-weight floor impact sounds through auditory experiments. Heavy-weight impact sounds were recorded in apartment buildings with a box-framed type reinforced concrete structure using a rubber ball. Temporal decay was quantified by using the decay rate (DR), defined as the sound pressure level (SPL) decrease per second [dB/s], and the distribution of DR for heavy-weight impact sounds was calculated. An auditory experiment was conducted in order to examine the just noticeable difference (JND) of DR, which was determined by the criteria of 75% correct answers by subjects. It was found that the JND of DR is around 11 dB/s. Based on the distribution and JND of DR, another experiment was conducted to investigate the effect of DR on annoyance perception of heavy-weight floor impact sounds in relation to the level differences. The results indicate that SPL and DR significantly influence annoyance perception; the scale value of annoyance increases with decreasing DR and increasing SPL. It was also found that the degree of satisfaction with regards to impact sounds can be improved by increasing DR, by controlling the sound field of the receiving room.
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