Artificial Reverberator Room Size Control via Time Warping
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Solution Overview
Problem
Current audio signal processing technologies lack a systematic way to manipulate the perceived size of a simulated acoustic space, leading to unwanted artifacts and Doppler shifts when changing room size, which is undesirable in musical applications.
Innovation Solution
An artificial reverberator that adjusts the room impulse response by stretching it in time and modifying the decay rate as a function of frequency, allowing for smooth changes in perceived room size without inducing Doppler shifts, achieved through resampling, warping, and scaling of time delays and feedback filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the room impulse response is stretched in time to increase perceived room size, then the perceived size is improved, but Doppler shifts are introduced that detune pitches
Solution Approach 1:
The patent implements dynamic control of reverberation parameters by processing the input signal through multiple parallel paths with different delay times and applying time-varying gain control. This allows the perceived room size to change smoothly over time without introducing Doppler shifts, as the system adapts its parameters dynamically rather than simply stretching the impulse response in time.
Solution Approach 2:
The reverberation system is divided into multiple parallel delay paths, each with its own delay time and gain control. By segmenting the single impulse response into multiple controlled paths, the system can independently adjust each path's contribution to achieve perceived room size changes without the harmful Doppler effects of uniform time-stretching.
2Volume of moving object
If controls driving common reverberators are changed to adjust room size, then the perceived size is improved, but zippering and other unwanted artifacts are produced in the output
Solution Approach 1:
The patent employs dynamic gain control on each delay path that responds smoothly to changes in the input signal and desired room size. This dynamic approach prevents abrupt parameter changes that would cause zippering artifacts, allowing smooth transitions while maintaining audio quality.
Solution Approach 2:
The system introduces intermediate processing stages including smoothing filters and gain control mechanisms between the input signal and the delay paths. These intermediary elements act as buffers that prevent direct, abrupt control changes from reaching the output, thereby eliminating zippering artifacts while still achieving perceived room size changes.
3Adaptability or versatility
If a systematic way to manipulate perceived room size is implemented, then control over room size is improved, but device complexity increases
Solution Approach 1:
The complex task of manipulating perceived room size is broken down into manageable segments: multiple parallel delay paths, each with independent but coordinated control. This segmentation makes the overall system more manageable and implementable while still achieving sophisticated control over perceived room size.
Solution Approach 2:
The patent implements a universal reverberation system that can produce multiple perceived room sizes using the same underlying structure. By making the delay paths and gain controls universally applicable to different room size configurations, the system achieves high adaptability without proportionally increasing complexity for each specific room size option.
Data Source
AI summary
In music recording and virtual reality applications, it is desired to control the perceived size of a synthesized acoustic space. In an embodiment, a room size parameter is used to modify characteristics of an artificial reverberator so as to affect a listener's sense of the size of the acoustic space. Properties of the reverberation related to perceived room size such as decay time and equalization are adjusted interactively.