Fig. 4From: The responses of subjective feeling, task performance ability, cortisol and HRV for the various types of floor impact sound: a pilot studyFrequency analysis of floor impact sounds (FIS) and their combinations. Abbreviation: Back, background; B, bang machine; T, tapping machine; I, impact ball; M, soundproof mattress; BT, B and T; TI, T and I; BI, B and I; BM, B with M; TM, T with M; IM, I with M; BTM, B and T with M; TIM, T and I with M; BIM, B and I with MBack to article page