Acoustics and Vibrations

Acoustics – the Science of Sound

We live in a sea of sound, of which only a small fraction is audible.  Acoustics research studies all aspects of sound (audible and inaudible): including generation, propagation, detection and even perception.   Acoustics offers challenges that are fundamental in nature and also broad in application.  Acoustics research carried out in the Mechanical Engineering Department can be broadly divided into the four following categories.

Aeroacoustics

This is the study of sound in the presence of an external flow and includes: sound generated by flow (e.g., noise from a jet engine), or sound production from fluid-structure interaction (e.g. sound generated by wind turbine, noise generated inside a jet engine, or sound generated by the vocal tract), or the interaction of sound with flow (sound propagation in a windy atmosphere).

Biomedical Acoustics

Investigates the application of acoustics, typically ultrasonic, for biomedical applications both diagnostic and therapeutic.  Diagnostic ultrasound applications include imaging of structures in the body and developing ultrasound specific contrast agents that can be targeted to specific disease site.  Therapeutic uses of ultrasound include shock waves to fragment kidney stones and the use of focused ultrasound to heat and destroy tissue.

Ocean Acoustics

Is the use of sound waves to probe the ocean environment.  This involves understanding how sound waves travel through the ocean, including interaction with the surface, the bottom sediment and bubbles and other structure in the water column.  Applications include tracking ocean going vessels, detecting mines and understanding the structure of the sea floor.

Physical Acoustics

The study of the fundamental physical processes involved in the propagation of sound waves and the used of sound waves to study the physical properties of matter.   Physical acoustics topics studied in ME include the interaction of sound with bubbles and the interaction of sound with light.

Vibrations

Is motion about an equilibrium point. At the human scale, a vast amount of research is aimed at reducing vibrations in order to reduce the associated noise. To achieve this reduction, our research is investigating the design and deployment of damping materials such as advanced composites. We also explore the vibrations of complex systems excited by force systems that are not well understood, such automotive brake assemblies. This work will eventually provide solutions for automotive brake squeal, which currently costs automotive companies approximately one billion dollars per year in North America alone. At the MEMS scale, our research investigates the vibration of high-Q resonators that are essential to cell phone and lab-on-chip technologies. In addition to improving the built world, our work investigates vibrations in the natural world.  In collaboration with biologists at Boston University, recent work has investigated the escape hatching of the red-eyed tree frog due to vibrational cues from predators.