Time domain wave separation using multiple microphones

Area of Science:

• Acoustics
• Mechanical Engineering
• Signal Processing

Background:

• Traditional acoustic measurements in tubular systems use steady-state or reflectometry methods.
• Reflectometry typically separates forward and backward waves using causality.
• Existing methods may not fully account for signal losses or gain variations.

Purpose of the Study:

• To present a multiple microphone reflectometry technique for acoustic wave separation in tubular systems.
• To enable accurate measurement of wave separation, bore profile, and input impedance.
• To improve upon existing time and frequency domain acoustic measurement methods.

Main Methods:

• Utilizes time domain convolution with multiple microphones to track acoustic waves.
• Employs two calibration runs to measure time domain transfer functions between microphone pairs.
• Incorporates time delay, frequency-dependent losses, and microphone gain ratios into the analysis.

Main Results:

• Successfully separates forward and backward acoustic waves in a cylindrical source tube.
• Demonstrates the application of the technique for measuring bore profile and input impedance.
• Provides a more comprehensive analysis by including inter-microphone transfer function effects.

Conclusions:

• The developed multiple microphone reflectometry technique offers an advanced approach to acoustic analysis in tubular systems.
• This method enhances accuracy by integrating wave separation with detailed transfer function characteristics.
• The technique provides a valuable tool for understanding and characterizing acoustic behavior in ducts and tubes.