Sir Arthur Harold Marshall KNZM (born 15 September 1931) is a New Zealand expert in acoustics design and research. He is Professor Emeritus of the University of Auckland School of Architecture, and co-founder of Marshall Day Acoustics Ltd in 1981 with Chris Day. He currently resides in Auckland New Zealand, and continues work with Marshall Day Acoustics as a group consultant. He is recognised internationally for his contribution to concert hall design, in particular his seminal work with Mike Barron on the importance of lateral reflections.