A frequency selective acoustic transducer for directional Lamb wave sensing.

Area of Science:

• Acoustics
• Materials Science
• Signal Processing

Background:

• Directional sensing of guided waves is crucial for applications like structural health monitoring.
• Traditional methods often require complex phasing and control of numerous channels.
• A need exists for simpler, more efficient directional acoustic transducers.

Purpose of the Study:

• To propose and investigate a novel frequency selective acoustic transducer (FSAT) with inherent directionality.
• To demonstrate the FSAT's capability for both directional sensing and generation of guided waves.
• To explore the application of the spiral FSAT for localizing acoustic events and active interrogation.

Main Methods:

• Design of a frequency selective acoustic transducer (FSAT) with a spiral configuration in the wavenumber domain.
• Theoretical formulation for continuously distributed active material in a shaped piezoelectric device to derive the spiral FSAT shape.
• Experimental validation using a discrete array approximating the continuous spiral geometry, tested with a scanning laser Doppler vibrometer.

Main Results:

• The spiral FSAT exhibits strong frequency-dependent directionality.
• Output signal's dominant frequency component is uniquely associated with the incoming wave's direction.
• The design enables directional sensing and generation without complex multi-channel control.

Conclusions:

• The spiral FSAT is a viable technology for frequency selective acoustic sensing.
• Its directional capabilities are suitable for localizing broadband acoustic events.
• The FSAT can be used for directional generation of Lamb waves in structural health monitoring.