Using a Retro-Reflective Membrane and Laser Doppler Vibrometer for Real-Time Remote Acoustic Sensing and Control

Area of Science:

• Acoustics
• Vibration Measurement
• Optical Sensing

Background:

• Traditional microphones have physical limitations in sound field control applications.
• Laser Doppler Vibrometers (LDVs) offer non-contact surface vibration measurement.
• Remote acoustic sensing is desirable for minimal invasiveness.

Purpose of the Study:

• To investigate the performance of retro-reflective film as an acoustic membrane for LDV-based sensing.
• To develop a remote acoustic sensing apparatus with minimal physical intervention.
• To demonstrate the feasibility of this apparatus in practical applications.

Main Methods:

• Theoretical analysis and systematic experiments were conducted on a retro-reflective film membrane.
• A Laser Doppler Vibrometer (LDV) was used to measure the vibration of the film.
• The apparatus was tested for sound pressure level sensing and active noise control.

Main Results:

• The developed apparatus can sense sound pressure levels above 20 dB within the 200 Hz to 4 kHz frequency range.
• Demonstrated applications include remote speech signal sensing and an active noise control headrest.
• A significant 22.4 dB noise reduction was achieved in the active noise control system (300 Hz to 6 kHz).

Conclusions:

• Retro-reflective film coupled with LDV provides a viable, minimally invasive remote acoustic sensing solution.
• The system offers advantages over traditional microphones, particularly in challenging acoustic environments.
• The technology shows significant potential for diverse applications in acoustic sensing and control.