In-Car Audio Loudness Control for Quiet Music Sections
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Solution Overview
Problem
Conventional in-car audio systems fail to account for the dynamic range of music, leading to inconsistent loudness ratios that result in quieter sections being masked by ambient noise, particularly in vehicles with varying speed-dependent noise levels.
Innovation Solution
A method and device that adjust the dynamic range of music based on vehicle speed and the music's dynamics, applying more gain to quiet sections to ensure they are audible over ambient noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If speed-dependent volume scaling is applied to compensate for ambient noise, then the overall loudness of music increases with vehicle speed, but the dynamic range of the music is compressed and quieter sections remain masked by noise
Solution Approach 1:
The system dynamically adjusts the gain factor based on both the ambient noise level (determined by vehicle speed) and the instantaneous loudness of the music signal. This dynamic adaptation allows the system to apply different gain factors to different sections of music, preserving the original dynamic range while ensuring quiet sections remain audible over ambient noise.
Solution Approach 2:
The system changes the gain parameter adaptively based on two inputs: vehicle speed (as a proxy for ambient noise level) and the measured loudness of the music signal. By modifying the gain parameter in response to these changing conditions, the system maintains constant loudness ratio between music and ambient noise without compressing the music's dynamic range.
2Object-affected harmful factors
If constant gain is applied to all music sections, then the overall volume can be increased to overcome ambient noise, but quiet sections of music are still masked by road noise
Solution Approach 1:
The system applies different gain factors to different local sections of the music signal based on their instantaneous loudness. Quiet sections receive higher gain factors while loud sections receive lower gain factors, ensuring that all sections maintain an appropriate loudness ratio relative to ambient noise without uniformly amplifying the entire signal.
Solution Approach 2:
The system continuously measures the loudness of the music signal and uses this feedback to adjust the gain factor in real-time. This feedback mechanism ensures that quiet sections are amplified sufficiently to overcome ambient noise while preventing over-amplification of already loud sections, thereby preserving the music's dynamic characteristics.
3Object-affected harmful factors
If dynamic range compression is applied to maintain constant loudness ratio, then quieter sections become audible, but the natural dynamics of the music are altered
Solution Approach 1:
The system uses dynamic gain adjustment based on real-time loudness measurement rather than static dynamic range compression. The gain factor changes dynamically with the music's instantaneous loudness and ambient noise level, allowing quiet sections to become audible while preserving the overall dynamic structure of the music through adaptive rather than compressive means.
Data Source
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AI summary
A method for automatically controlling loudness of an audio signal to be replayed within a vehicle is provided. The method comprises an automatic loudness measurer measuring a loudness of an incoming audio signal that comprises a sequence of digital audio blocks. Furthermore, a noise level indication signal is received which indicates a noise level within the vehicle and a processor calculates a gain factor based on the measured loudness of the incoming audio signal and the noise level indication signal. If the measured loudness is equal to or above a predefined first target loudness (TLamS), the gain factor is zero. Otherwise, if the noise level indication signal indicates a noise level equal to or above a predefined intermediate noise level, the gain factor is a difference between the measured loudness and a current target loudness, limited to a maximum gain, wherein the maximum gain is a defined absolute maximum gain, and the current target loudness is linearly interpolated, according to the noise level indication signal, between a predefined second target loudness (TLaiS) for the noise level being equal to said intermediate noise level and the predefined first target loudness (TLamS) for the noise level being equal to a predefined maximum noise level. Otherwise, if the noise level indication signal indicates a noise level below the intermediate noise level, the gain is linearly interpolated, according to the noise level, between the gain as defined for the intermediate noise level and zero. Furthermore, the gain factor is applied to the audio signal to be replayed.