Harmonic Vibrations and Acoustics

Prediction of structure-borne noise and sound propagation can play important roles in the design of many products. Examples include noise caused by vibrating structural components, transmission of sound through thin panels and the acoustic performance of piezoelectric devices.

Solving these types of acoustic wave propagation problems (and many more) can be performed in a coupled way, in which the fluid and structural domains are solved simultaneously, or in an uncoupled way, in which the structural analysis is performed first, followed by the acoustics analysis. The former is used when both structural vibrations and acoustic waves have a mutual influence: think of a thin speaker cone whose deformations will be influenced by the pressure waves. The latter can be used when the acoustic waves do not affect the vibration of the structure, as is often the case for massive parts.

The video below demonstrates how you can easily perform a coupled acoustics simulation on a loudspeaker.

Watch and learn how to compute the acoustical properties of a speaker, including sound-pressure level, directivity and far-field results.

The first step in creating a coupled acoustics simulation is to add the acoustics portion of the model. This is usually done by creating an enclosure around the structural model, such as a sphere.

Speaker Structural Model
Structural model of the speaker and surrounding acoustics volume

Then the various constituents of the simulation are defined: the materials that comprise the structures, identification of the acoustic bodies, and the properties of the acoustic medium, such as air in our case. It is also very important to define the location of the interface between the structure and the air, so vibration velocities can be transferred as input for the acoustics analysis.

Acoustic Volume Interface
Identification of the acoustic volume and its interface with the vibrating structure

Once the computation has been performed, the engineer can review the acoustics results, such as the acoustic pressure, the sound pressure level or the directivity of the speaker.

Acoustic Pressure Field
Acoustic pressure field

SPL Polar Diagram
Polar plot showing directivity of the loudspeaker