Timbre Control via Noise-Extracted Room Impulse Response Estimation
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Solution Overview
Problem
Existing acoustic control systems face challenges in accurately estimating the room impulse response (RIR) due to external influences like background noise, which affects signal-to-noise ratio and requires time to adapt, leading to suboptimal sound quality in small rooms such as vehicle cabins.
Innovation Solution
A system comprising a loudspeaker, microphone, adaptive filter, noise extraction block, gain control block, and gain-shaping block that estimates the room transfer function, extracts ambient noise, and adjusts the sound signal gain based on volume settings and room-dependent gain to control timbre, using techniques like the delayed coefficients method and frequency domain adaptive filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If noise-dependent equalization control is used to compensate for room acoustic effects, then timbre control is improved, but measurement precision deteriorates due to background noise affecting RIR estimation
Solution Approach 1:
The patent introduces an intermediary signal processing approach where the system separates the estimation of room impulse response from ambient noise through spectral analysis. The noise extraction block acts as an intermediary that isolates ambient noise components from the total sound signal, allowing the RIR estimation to proceed without contamination from background noise, thus resolving the measurement precision issue while maintaining timbre control capability
Solution Approach 2:
The patent segments the total sound signal into distinct components: the desired sound from the loudspeaker, the room impulse response, and ambient noise. By applying spectral analysis and separating these components in the frequency domain, the system can estimate RIR independently of ambient noise, thereby improving measurement precision while preserving the ability to control timbre through equalization
2Adaptability or versatility
If adaptive filtering is used to estimate room impulse response, then timbre control capability is improved, but adaptation time increases due to noise interference
Solution Approach 1:
The patent applies preliminary action by extracting and characterizing ambient noise before it interferes with the RIR estimation process. The noise extraction block continuously monitors and characterizes ambient noise in advance, allowing the adaptive filter to compensate for noise effects proactively rather than reacting after degradation occurs, thus reducing adaptation time while maintaining timbre control capability
Solution Approach 2:
The patent implements feedback mechanisms where the estimated ambient noise signal is continuously fed back into the RIR estimation process. This feedback loop allows the system to dynamically adjust its estimation in real-time, compensating for noise interference without requiring lengthy adaptation periods, thereby reducing loss of time while preserving timbre control capability
3Reliability
If room acoustic effects are compensated through equalization, then speech intelligibility is improved, but device complexity increases due to multiple processing blocks
Solution Approach 1:
The patent applies universality by designing the noise extraction and RIR estimation blocks to serve multiple functions simultaneously. The same spectral analysis machinery used for noise extraction also provides information for RIR estimation and timbre control, reducing the need for separate dedicated components and thereby reducing device complexity while maintaining speech intelligibility improvements
Data Source
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AI summary
A system and method for automatically controlling the timbre of a sound signal in a listening room are also disclosed, which comprise the following: producing sound in the time domain from a re-transformed electrical sound signal in the time domain, in which an electrical sound signal in the time domain being transformed into electrical sound signal in the frequency domain and the electrical sound signal in the frequency domain being re-transformed into the re-transformed electrical sound signal; generating a total sound signal representative of the total sound in the room, wherein the total sound comprises the sound output from the loudspeaker and the ambient noise in the room; processing the total sound signal to extract an estimated ambient noise signal representing the ambient noise in the room; and adjusting the spectral gain of the electrical sound signal in the frequency domain dependent on the estimated ambient noise signal, the electrical sound signal and a room dependent gain signal. The room dependent gain signal being determined from reference room data and estimated room data.