Microphone Transfer Function Characterization via Self-Generated Test Signals
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Solution Overview
Problem
Accurately characterizing the acoustic characteristics of an environment is challenging when using a microphone with unknown transfer function, leading to incorrect correction of sound output and degraded audio quality due to unknown distortions or filtering associated with the microphone.
Innovation Solution
An electronic device with a microphone determines its own transfer function by performing acoustic measurements near and far from a speaker, using predefined transfer functions of the speaker to calculate the microphone's transfer function and subsequently the environment's transfer function, allowing for correction of sound output to reduce room modes and improve audio quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If acoustic measurements are performed using a microphone with unknown transfer function, then the measurement process can be simplified, but the measurement precision deteriorates due to unknown distortions and filtering
Solution Approach 1:
The electronic device performs self-characterization by using its own speaker to generate test signals and its own microphone to measure the acoustic response. The processor calculates the transfer function of the microphone by comparing the electrical drive signal with the actual acoustic measurements, enabling the device to self-correct its measurement capabilities without requiring external calibration equipment with known characteristics.
Solution Approach 2:
The system performs preliminary characterization of the microphone's transfer function before conducting actual acoustic measurements of the environment. By first determining the microphone's frequency response and distortion characteristics through controlled tests near the speaker, the system prepares correction data that will be applied during subsequent environmental measurements, ensuring accurate results.
2Ease of operation
If the microphone's transfer function is not characterized, then the measurement process is simpler, but the reliability of audio correction deteriorates
Solution Approach 1:
The electronic device autonomously characterizes its own microphone by generating test signals through its speaker and measuring the acoustic response with its microphone. The processor automatically calculates the transfer function and uses it to correct subsequent measurements, eliminating the need for manual calibration or external reference equipment while ensuring reliable audio correction.
3Measurement precision
If acoustic measurements are performed at multiple locations in the environment, then the accuracy of environment characterization improves, but the measurement time increases
Solution Approach 1:
The system performs preliminary characterization of the microphone's transfer function in a controlled position near the speaker before conducting environmental measurements. This pre-calibration step ensures that subsequent measurements at multiple locations in the environment can be accurately corrected, improving the reliability of room mode identification and transfer function determination.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables accurate determination of the environment's acoustic characteristics, improving audio quality by correcting for the microphone's and environment's effects, allowing for better sound reproduction and listener experience.
Implementation Method 1
when an alternating-current electrical signal is applied to a voice coil in a loudspeaker (such as a wire coil suspended in the gap between the poles of a permanent magnet), the voice coil, and a speaker cone coupled to the voice coil, move back and forth. The motion of the speaker cone produces sound in an audible frequency range.
Implementation Method 2
a microphone with predetermined acoustic characteristics is used to perform measurements in the environment
Data Source
AI summary
An electronic device with a microphone is used to determine a transfer function of an environment (and, more generally, an acoustic characteristic). In particular, the electronic device may use the microphone to perform acoustic measurements when the electronic device is proximate to a speaker in the environment. Then, based on the acoustic measurements and a first predetermined transfer function of the speaker, the electronic device may calculate a transfer function of the microphone in a band of frequencies. Moreover, the electronic device may use the microphone to perform additional acoustic measurements in the environment that includes the speaker. Next, based on the additional acoustic measurements, the transfer function of the microphone and a second predetermined transfer function of the speaker, the electronic device may determine the transfer function of the environment in the same or a different band of frequencies.