Time-selective windowing technique in free-field microphone reciprocity calibration
Hyu-Sang Kwon1, Wan-Ho Cho, Sang-Joon Suh
1Center for Fluid Flow and Acoustics, Division of Physical Metrology, Korea Research Institute of Standards and Science 267, Gajeong-ro, Yuseong-gu, Daejeon 305-340, Korea. hyusang@kriss.re.kr
The Journal of the Acoustical Society of America
|July 19, 2013
Summary
This study introduces a novel Dolph-Chebyshev window filter to improve microphone reciprocity calibration. The new method enhances low-frequency accuracy by reducing signal overlap and extending the calibration range below 2 kHz.
Area of Science:
- Acoustics
- Signal Processing
- Metrology
Background:
- Time-selective windowing is crucial for microphone reciprocity calibration, removing multi-path noise.
- Existing methods face limitations with overlapping signals, especially at low frequencies and for high Q microphones.
- Fast Fourier Transform (FFT) analysis reveals frequency range limitations exacerbate signal overlap issues.
Purpose of the Study:
- To address limitations in low-frequency microphone reciprocity calibration caused by signal overlap.
- To propose an improved filtering technique for more accurate calibration.
- To extend the usable frequency range for free-field reciprocity calibration.
Main Methods:
- Utilized a Dolph-Chebyshev window filter, known for its low sidelobe levels, as an alternative to conventional low-pass filters.
- Applied time-selective windowing to mitigate multi-path noise.
- Incorporated an inverse filter to compensate for distortions introduced by the applied filter.
Main Results:
- Successfully reduced signal overlap issues, particularly at low frequencies.
- Demonstrated the effectiveness of the Dolph-Chebyshev window in minimizing leakage from limited frequency ranges.
- Extended the achievable frequency range for free-field reciprocity calibration below 2 kHz.
Conclusions:
- The proposed Dolph-Chebyshev windowing technique offers a significant improvement over conventional methods for microphone reciprocity calibration.
- This method effectively overcomes low-frequency limitations and enhances the accuracy of calibration.
- The study successfully expands the application scope of free-field reciprocity calibration to lower frequencies.
