Editorial for special issue for Michael J. Brennan

Michael John Brennan’s professional journey was defined by a rare combination of technical mastery and a lifelong commitment to making complex dynamics accessible to the global engineering community. After beginning his career in the United Kingdom, he established himself as a central figure at the University of Southampton’s Institute of Sound and Vibration Research (ISVR). It was there that he earned his MSc with distinction in 1992 and his PhD in 1995, eventually rising to the rank of Full Professor. During his fifteen years at the ISVR, he became widely recognized for his work on active vibration control and structural dynamics, while also serving as a dedicated supervisor of PhD students and a prolific author of Journal of Sound and Vibration (JSV) papers. In 2010, Mike began a significant new chapter by moving to Brazil, where he joined the S˜ao Paulo State University (UNESP). As a Research Professor at the Ilha Solteira campus, he played a transformative role in elevating the university's global standing. Throughout his tenure in Brazil, he remained a remarkably productive researcher, co-editing the prominent monograph on the Duffing Equation in 2011 and publishing ‘Virtual Experiments in Mechanical Vibrations’ in 2022. His immense contribution to the field is reflected in over 500 publications and >21,000 citations, leading to his recognition as a Professor Sˆenior of UNESP and Emeritus Professor of the University of Southampton. A central pillar of this career was his relationship with the JSV, where he published continuously for more than thirty years starting in 1995. As one of the journal's most active contributors, he has authored >80 articles covering diverse fields in both acoustics and vibration. These JSV papers alone have attracted >8100 citations, including a landmark co-authored paper with nearly 1000 citations and 21 other works that have each surpassed the 100-citation mark. His enduring impact is best measured through his wide network of collaborators and many PhD students he guided, as well as the countless readers and followers of his research who continue to be inspired by his unique style and creativity. To honour these monumental contributions and celebrate his 70th birthday, the Journal of Sound and Vibration has compiled a Virtual Special Issue dedicated to Mike’s legacy. For this collection, several of his invited co-authors selected a JSV paper they had written with Mike which they found to be particularly impactful. These selected works form the core of the Virtual Special Issue, serving as a tribute to his collaborative spirit and scientific reach. In addition to the papers themselves, each contributor provided a short reflection explaining the significance of their chosen work; these insights are included into this Editorial, arranged chronologically by publication year to provide a historical perspective on Mike’s evolving influence over the decades. We take this opportunity to thank Michael Brennan for his immense and tireless contributions to the Journal of Sound and Vibration and the wider research and engineering community, which have shaped the way we understand and communicate vibro-acoustics today. We also invite readers to explore these selections and reflections, and we join his many colleagues, students, and friends in wishing him a very happy 70th birthday.