At July 1st, both Yi Qin and Indra Sihar will defend their PhD theses.

applicable to other types of lightweight floors.

Indra Sihar present his work titled: Numerical modelling of transient low-frequency sound propagation and vibration in buildings. His defense starts at 11AM sharp and can be attended online via this Teams link, or at the TU/e campus (Atlas Building Room 0.710). The full thesis can be downloaded here, and the summary is as follows: The urban environment is increasingly exposed to excessive noise from environmental noise sources and neighbours. To address this problem, an acoustically high-quality built environment is needed to ensure health and comfort. In designing such an environment, the prediction of sound propagation and vibrations in buildings have a vital role. This research aims to develop an efficient yet detailed numerical model of sound propagation and vibration in building applications, especially in the low-frequency range. This research employs a wave-based method to solve these problems. The chosen wave-based method is the time-domain discontinuous Galerkin (DG) method due to its favourable features such as computational efficiency, high-order accuracy, geometric flexibility, and the potential for massive parallel computing. This dissertation consists of three main parts. In the first part, the DG method is applied for sound propagation in air. The applications include room acoustics and outdoor sound propagation in the presence of wind flow. Examples include sound propagation in an experimental chamber and at an airport environment. In the second part, the DG method is developed for the structural vibrations of monolithic structures and structures with piece-wise constant properties. Examples include vibrations of rectangular plates, L- and T-shaped structures, and a scaled lightweight wooden floor. The third part expands the DG method to solve the sound and vibration interaction (vibroacoustic) problems. This part presents the impact sound radiation from a rectangular slab and sound transmissions of several walls as examples.

Yi Qin present his work titled: Characterization of impact sound from lightweight joist floors. His defense starts at 4PM sharp and can be attended online via this Teams link, or at the TU/e campus (Atlas Building Room 0.710, however Yi Qin will defend online himself). The full thesis can be downloaded here, and the summary is as follows: Impact sound is one of the major concerns relating to the quality of indoor acoustic environments. The lightweight floors commonly built in residential dwellings are very ineffective at insulating impact sounds, especially in the low-frequency range, due to their low weight and low damping. Unfortunately, most impact forces caused by human activities, such as walking and jumping, have significant energy at low frequencies. With the increasing use of wood-framed multi-family buildings, this low-frequency impact noise has led to an increasing number of complaints by the people living in these dwellings.
This PhD work has numerically and experimentally investigated the dynamic and acoustic responses of lightweight joist floors in the low-frequency range (<200Hz). The main objectives of this PhD project are i) to propose an improved experimental method to characterize the low-frequency impact sound of a lightweight floor using transfer functions, ii) to develop a fast prediction model allowing accurate evaluation of the vibro-acoustic performance of a joist floor, and iii) to examine the efficiency of multiple dynamic vibration absorbers (DVAs) as a measure for reducing the low-frequency vibration of a joist floor. Joist floors consisting of wood-based plates and beams were used in this study. Some of the research outcomes, such as the measurement method, the application of dynamic vibration absorbers, and the optimization method can be