Rotary Speaker Sound Emulation via Pre-computed Impulse Responses
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Solution Overview
Problem
Existing electronic musical instruments fail to reliably imitate the sound of a rotary speaker due to simple modulation signals and high computational load for convolution calculations, leading to increased component costs.
Innovation Solution
A musical sound signal generation apparatus that stores waveform data expressing sounds emitted by a rotary speaker and changes reproduction speed without altering pitch or formant, using a pitch synchronous overlap and add method to imitate the rotary speaker effect without complex calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If convolution calculations are used to imitate rotary speaker effect, then sound imitation accuracy is improved, but computational load and device complexity increase
Solution Approach 1:
The patent pre-calculates and stores impulse responses for multiple rotor rotation angles in advance. Instead of performing convolution calculations in real-time, the system selects pre-computed impulse responses based on the current rotation angle, significantly reducing computational load while maintaining sound imitation accuracy.
Solution Approach 2:
The patent pre-calculates and stores impulse responses for multiple rotor rotation angles in advance. Instead of performing convolution calculations in real-time, the system selects pre-computed impulse responses based on the current rotation angle, significantly reducing computational load while maintaining sound imitation accuracy.
2Device complexity
If modulation circuits are used to reproduce rotary speaker effect, then device complexity is reduced, but sound imitation accuracy deteriorates
Solution Approach 1:
The patent records actual impulse responses from a real rotary speaker at different rotation angles and stores them in memory. This copying approach captures the authentic acoustic characteristics of the rotary speaker without requiring complex real-time modulation circuits, achieving high sound imitation accuracy with simplified hardware.
3Adaptability or versatility
If rotation speed is changed to imitate fast/slow effects, then adaptability is improved, but maintaining pitch and formant becomes difficult
Solution Approach 1:
The patent pre-computes and stores multiple impulse responses corresponding to different rotor rotation angles and rotation speeds. When the rotation speed changes, the system selects the appropriate pre-computed impulse response that maintains the correct pitch and formant characteristics, avoiding the need for real-time pitch correction while adapting to different rotation speeds.
Data Source
AI summary
An electronic musical instrument includes a storage unit storing waveform data WD constituted by a plurality of sample values, the waveform data expressing an acoustic waveform of a musical sound emitted from a speaker while a rotor rotates about a rotation axis by a predetermined angle, and a reproduction unit configured to sequentially read out the sample values from the storage unit and generate a musical sound signal based on the read-out sample values, the reproduction unit being configured to change a reproduction speed of the musical sound expressed by the plurality of sample values, without changing a pitch and formant of the musical sound.