Generalized radiation modes and microphone arrays for close-talking

Area of Science:

• Acoustics
• Signal Processing
• Array Design

Background:

• Selective near-field sound measurement is crucial for improving signal-to-noise ratio in close-talking applications.
• Existing methods may not optimally distinguish near-field from far-field sound.
• Mobile phones and similar devices benefit from enhanced audio capture.

Purpose of the Study:

• To apply the theory of generalized radiation modes for designing microphone arrays.
• To maximize the near-to-far sound ratio for selective near-field sound measurement.
• To develop a method for optimizing microphone array performance in close-talking scenarios.

Main Methods:

• Formulating generalized radiation modes as a generalized eigenvalue problem.
• Relating eigenvalues to the near-to-far ratio and eigenvectors to modal shapes (microphone amplitudes/phases).
• Designing the microphone array based on the eigenvector with the largest eigenvalue.

Main Results:

• The real eigenvalue directly corresponds to the near-to-far ratio for each mode.
• The real eigenvector defines the optimal amplitudes and phases for individual microphones.
• Computer simulations verified the theory and demonstrated effectiveness.

Conclusions:

• The proposed method effectively designs microphone arrays for selective near-field sound measurement.
• Maximizing the near-to-far ratio enhances signal quality in close-talking applications.
• The approach offers advantages over conventional gradient microphones, as shown in numerical examples.