Head-Tracked Loudspeaker Switching for Balanced Stereo Reproduction

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Solution Overview

Problem

Conventional loudspeaker systems installed in seats fail to provide balanced stereo sound reproduction when a listener's head position deviates from the midpoint between left and right loudspeakers, leading to unbalanced sound volumes and potential distortion, especially when the head is closer to one loudspeaker, resulting in lack of information from the more distant loudspeaker.

Innovation Solution

A signal reproduction apparatus that adjusts the levels of right and left channel signals and switches input states to loudspeakers based on the listener's head position, using detection and level adjustment parts to ensure balanced sound reproduction without exceeding loudspeaker input tolerance and minimizing sound leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the left channel signal and the right channel signal are respectively reproduced at the same level at the left loudspeaker and the right loudspeaker, then the stereo reproduction is balanced when the listener is at the midpoint, but the sound balance becomes unbalanced when the listener's head shifts closer to one loudspeaker

Engineering Contradiction:

Improvesound balanceVSAvoidadaptability to head position

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamics by making the signal input configuration changeable based on detected head position. The system switches between different input states (first, second, and third input states) depending on whether the head is at the midpoint, closer to the left loudspeaker, or closer to the right loudspeaker. This dynamic adaptation ensures balanced sound reproduction regardless of head position.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the signal level parameters dynamically based on head position detection. When the head is closer to one loudspeaker, the system increases the level of the signal from the more distant loudspeaker and decreases the level from the closer loudspeaker, thereby maintaining overall sound balance across different listening positions.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the head of the listener is closer to one loudspeaker, then the sound from that loudspeaker is loudly perceived, but the sound from the more distant loudspeaker becomes too soft and information is lost

Engineering Contradiction:

Improvesound output levelVSAvoidinformation from distant loudspeaker

Core Design Contradiction:

Use of energy by moving objectVSLoss of information

Solution Approach 1:

The patent adjusts signal level parameters based on head position to compensate for distance effects. When the head is closer to one loudspeaker, the system increases the gain of the signal from the more distant loudspeaker, ensuring that both channels contribute equally to the perceived sound and no information is lost.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs feedback by using a detection part to detect head position and then using this information to adjust the signal levels accordingly. The detection part provides feedback about the listener's position, and the signal processing part uses this feedback to optimize the sound output, preventing information loss from the more distant loudspeaker.

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If the loudspeaker is installed near the head of the listener, then the reproduced sound can be heard even at low levels and sound leakage is suppressed, but the input signal level must be carefully controlled to prevent distortion

Engineering Contradiction:

Improvesound leakageVSAvoidsignal input tolerance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent carefully controls signal level parameters to match the specific characteristics of the built-in loudspeakers. By adjusting the signal levels according to head position and loudspeaker characteristics, the system ensures optimal sound output without exceeding the input tolerance of the compact loudspeakers, thereby preventing distortion while maintaining low sound leakage.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250344030A1Signal reproduction device, signal reproduction method, and non-transitory computer readable recording medium storing signal reproduction program

Publication Date: 2025.11.06 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A signal reproduction apparatus adds a right channel signal having an adjusted level and a left channel signal having an adjusted level, and makes switching of input states to a first loudspeaker and a second loudspeaker according to the detected position of the head of the listener between: a first input state in which the right channel signal is input to the first loudspeaker and the left channel signal is input to the second loudspeaker; a second input state in which an output signal from an addition part is input to the second loudspeaker and both the right channel signal and the output signal are kept from being input to the first loudspeaker; and a third input state in which the output signal is input to the first loudspeaker and both the left channel signal and the output signal are kept from being input to the second loudspeaker.