Microphone Equalization Using Loudspeaker Feedback for Room Acoustics
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Solution Overview
Problem
In telephony and speakerphone scenarios, the sound quality is compromised due to overboosting or distortion of low-frequency content, particularly in various acoustic environments such as rooms and vehicles, affecting both the listener and speaker.
Innovation Solution
A microphone equalization system comprising a loudspeaker with an internal sensor and an external microphone, which determines an equalization filter by comparing signals from the internal and external sensors to compensate for acoustic environment effects, thereby improving sound quality by spectral shaping of microphone signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If digital equalization is performed to compensate for room acoustics effects on loudspeaker output, then frequency response balance is improved, but low frequency content becomes overboosted or distorted in hands-free telephony scenarios
Solution Approach 1:
The system uses feedback from an internal sensor in the loudspeaker enclosure to detect the actual acoustic pressure waves being produced, and compares this with the input signal to automatically determine appropriate equalization filter settings that compensate for room effects without causing low frequency distortion
Solution Approach 2:
The system dynamically changes the equalization filter parameters based on the detected acoustic environment and measured low frequency response, adjusting the frequency and gain characteristics to maintain balance while preventing overboosting in hands-free scenarios
2Manufacturing precision
If microphone equalization is applied to compensate for acoustic environment effects, then sound quality is improved, but system complexity increases due to additional sensors and processing
Solution Approach 1:
The internal sensor in the loudspeaker enclosure serves multiple functions: it monitors the acoustic pressure waves for equalization purposes, detects low frequency content for distortion prevention, and provides feedback for automatic filter determination, eliminating the need for separate dedicated sensors
Solution Approach 2:
The system uses the loudspeaker's own internal sensor and acoustic output as the measurement source, allowing the device to self-diagnose and self-adjust its equalization settings without requiring external calibration equipment or additional specialized sensors
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
The system automatically enhances sound quality by reducing boomy or bass-heavy perceptions, ensuring a more balanced frequency response for both uplink and downlink signals during telephony calls, without requiring user intervention.
Implementation Method 1
A sensor is located inside the back volume... while the driver diaphragm produces acoustic pressure waves from its rear face and from its front face, that are sensed by the sensor and the external microphone respectively
Implementation Method 2
the external microphone is located 'outside' the loudspeaker, at a location that is preferably close to and directly open to the 'front face' of the driver diaphragm in order to sense the effect of the acoustic environment upon the acoustic pressure waves
Data Source
AI summary
A microphone equalization system determines an equalization filter which is used to spectrally shape a signal from a microphone. A loudspeaker has an enclosure, a back volume, a driver diaphragm, and a sensor located inside the back volume. An external microphone is located outside the loudspeaker. A processor determines the equalization filter based on comparison of a first signal from an output of the sensor and a second signal from an output of the external microphone both of which are produced while the driver diaphragm produces acoustic pressure waves produced by the driver diaphragm. The processor is to then spectrally shape a third signal from the output of the external microphone that is responsive to further acoustic pressure waves from a source other than the loudspeaker. Other aspects are also described and claimed.