Mobile Audio Room Correction Without a Reference Microphone
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Solution Overview
Problem
Existing room correction methods for audio systems using mobile devices are inadequate due to the unknown and varying frequency responses of mobile device microphones, leading to unsatisfactory results in adapting the frequency response at the desired listening position.
Innovation Solution
A method utilizing a mobile device's built-in microphone to record audio test sounds at near-field and far-field positions, processing these recordings to extract frequency response curves, and modeling correction filters to eliminate room-gain effects, allowing for improved room correction irrespective of the microphone's frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference microphone with known frequency response is used for room correction measurement, then measurement accuracy is improved, but device complexity and user burden increase
Solution Approach 1:
The mobile device's built-in microphone performs room correction measurements without requiring an external reference microphone. The system uses the mobile device itself to play test sounds and record the acoustic response, making the device self-sufficient for room correction tasks.
Solution Approach 2:
Instead of using a dedicated reference microphone with known frequency response, the patent uses the mobile device's built-in microphone and compensates for its unknown frequency response through calibration procedures and algorithms that work around the microphone's characteristics.
2Ease of operation
If mobile device microphones are used for room correction, then ease of operation is improved, but measurement precision deteriorates due to unknown frequency responses
Solution Approach 1:
The patent transforms the problem by changing the approach from directly measuring frequency response to measuring relative differences. By playing test sounds at different positions and comparing the recorded responses, the system extracts room acoustic characteristics without needing to know the absolute microphone frequency response.
Solution Approach 2:
The system uses feedback loops where the mobile device plays test sounds, records the response through its built-in microphone, processes the data to determine room characteristics, and then applies correction filters to the audio output based on the analyzed room response.
3Device complexity
If built-in microphones are used instead of separate reference microphones, then device complexity is reduced, but reliability of room correction deteriorates
Solution Approach 1:
The mobile device's built-in microphone serves multiple functions: it acts as both the playback device's acoustic output monitor and the measurement microphone for room correction. This multi-functionality eliminates the need for separate reference microphones while maintaining room correction capability.
Solution Approach 2:
The patent introduces software algorithms and processing routines as intermediaries between the built-in microphone and the room correction analysis. These algorithms compensate for the microphone's unknown frequency response characteristics and extract accurate room acoustic information from the recorded signals.
Data Source
AI summary
A method of performing room correction for an audio system using a mobile device, including at least one microphone having an unknown microphone frequency response characteristic, includes obtaining a near-field sound recording of a first instance of an audio test sound, obtaining a far-field sound recording of a second instance of the audio test sound, processing the near-field and far-field sound recording and modelling one or more correction filters for application on audio signals of the audio system. The correction filter corrects audio signals to a target frequency response characteristic at the far-field position, e.g. a user's listening position.