Sound Generating Device for Electronic Keyboard Instrument

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In electronic keyboard instruments, sound wave interference occurs due to the overlap in frequency ranges between tweeters and woofers, leading to unstable acoustic characteristics, especially when the audience is positioned at different distances from these speakers.

Innovation Solution

A sound generating device with a speaker unit comprising a tweeter and a woofer directed in opposite directions, utilizing a separation unit with high pass and low pass filters to separate signals into non-overlapping frequency bands, ensuring that the tweeter and woofer produce distinct frequency ranges, and optionally including a squawker to reduce distance differences with the audience.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If both tweeter and woofer are directed upwardly and disposed at different horizontal positions, then the speaker unit can be compactly arranged, but sound wave interference occurs due to distance differences from listening points

Engineering Contradiction:

Improvespeaker unit arrangementVSAvoidacoustic characteristic stability

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent divides the frequency spectrum into distinct bands using a separation unit with high-pass and low-pass filters, assigning frequencies to either the tweeter or woofer without overlap. This segmentation eliminates frequency overlap and the resulting sound wave interference, resolving the acoustic characteristic instability while maintaining the compact upward-directed speaker arrangement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The separation unit acts as an intermediary between the audio signal and the speakers, filtering and separating frequencies before they reach the tweeter and woofer. This intermediary component ensures that each speaker receives only its designated frequency range, preventing interference and stabilizing acoustic characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If frequencies are overlapped between tweeter and woofer allocation, then simpler band division is used, but acoustic characteristic runaway occurs due to sound wave interference

Engineering Contradiction:

Improveband division complexityVSAvoidacoustic characteristic stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent replaces simple mechanical frequency overlap with an electronic filtering system. The separation unit uses electronic high-pass and low-pass filters to digitally separate frequencies, achieving precise frequency allocation without mechanical complexity. This electronic approach provides stable acoustic characteristics while maintaining manageable system complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If tweeter and woofer are directed in opposite directions, then frequency overlap is prevented, but more complex signal separation is required

Engineering Contradiction:

Improveacoustic characteristic stabilityVSAvoidsignal separation complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the frequency parameter distribution by using a separation unit that dynamically adjusts signal frequencies based on the opposite-direction speaker arrangement. The high-pass and low-pass filters modify the frequency parameters of signals sent to each speaker, ensuring non-overlapping frequency bands that match the opposite directional orientation, thereby stabilizing acoustic characteristics.

Inventive Principle:

Principle #35Parameter changes

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

This configuration prevents sound wave interference, stabilizes acoustic characteristics, and provides a more consistent sound experience by minimizing acoustic characteristic variations at listening points, mimicking the sound propagation of an acoustic piano.

Implementation Method 1

a separation unit having a high pass filter and a low pass filter and adapted to separate a signal obtained from a same source into first and second signals which do not overlap in frequency band each other

Methodology Applied

Scientific EffectFrequency filtering: Filter (electronic)

Data Source

PatentUS8084680B2Sound generating device of electronic keyboard instrument

Publication Date: 2011.12.27 YAMAHA CORP

AI summary

A sound generating device of an electronic keyboard instrument, which eliminates overlap between frequency bands to avoid sound wave interference to stabilize acoustic characteristic. Woofers are disposed at a bottom part of a speaker box and directed downward, and squawkers are disposed at an upper part of the speaker box and directed upward. In a DSP, waveform data selected from waveform data groups are input into a MIX, and a waveform signal containing high and low frequency band components is produced from a signal output from the MIX. In a distributor, the waveform signal is converted into an analog signal which is then separated into a musical tone signal only containing the high frequency band component and a musical tone signal only containing the low frequency band component, and these musical tone signals between which there is no frequency band overlap are supplied to the tweeter and the woofer.