Proposal of an environmental vibration measurement method to reduce contact resonance errors using vibration control materials

Accurate measurement of environmental vibrations in buildings can be significantly affected by “contact resonance,” which arises when vibration sensors are placed on soft floor coverings, such as carpets or tatami mats. This phenomenon is caused by the mass of the sensor and the spring-like behavior of the floor covering. It results in measurement errors that particularly affect low-frequency vibration acceleration levels. To address this issue, we propose a novel measurement method that uses vibration control materials to minimise the impact of contact resonance. Introducing a layer of soft, vibration-isolating material between the sensor and the floor surface shifts the resonance frequency to a lower range. This allows for a more accurate estimation of the true vibration response of the underlying structure. The method applies a correction based on vibration transmission characteristics using patterns measured on site or in advance. The proposed approach was validated through experimental studies on carpeted floors and tatami mats, demonstrating a significant reduction in resonance-induced errors. Even for traditional thick tatami mats, a modified estimation method provided reasonably accurate results. This technique enables reliable vibration measurements to be taken without removing floor finishes, which is particularly useful for field surveys in occupied buildings.