Masking Sound Generator Using Envelope Randomization
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Solution Overview
Problem
Existing masking sound systems often produce noisy or unnatural sounds due to the simultaneous emission of target and masking sound signals with similar frequency components, making it difficult to prevent overhearing effectively.
Innovation Solution
A masking sound generating apparatus that divides audio signals into frequency bands, generates envelope signals, randomizes sections of these signals within specific thresholds, and multiplies them by corresponding frequency band signals to create band masking signals, which are then added to produce a masking sound that reduces intelligibility and avoids noisy or unnatural perceptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a masking sound system emits both target sound signal and masking sound signal simultaneously with similar frequency components, then the masking effect is achieved to prevent overhearing, but the listener perceives noisy or unnatural sound
Solution Approach 1:
The audio signal is divided into multiple frequency bands, and each band is processed independently to generate corresponding band masking signals. This segmentation allows different frequency components to be masked separately, preventing the accumulation of unnatural perceptions across the entire frequency spectrum while maintaining effective masking coverage.
Solution Approach 2:
Different masking strategies are applied to different frequency bands based on their specific characteristics. The envelope signals for each frequency band are randomized independently within specific threshold ranges, creating locally optimized masking that adapts to the natural variability of speech in different frequency regions, thereby avoiding uniform noisy perception.
2Reliability
If the envelope signal is heavily randomized to improve masking effectiveness, then the masking sound becomes more effective, but the original sound's intelligibility may be compromised
Solution Approach 1:
The envelope signal randomization is applied partially rather than completely - only to sections with amplitudes between specific thresholds (greater than a first threshold and less than a second threshold). This partial action provides sufficient masking effectiveness for mid-level signals while preserving the intelligibility of prominent speech components that fall outside the threshold range.
Solution Approach 2:
The randomization process changes the amplitude parameter of envelope signals within controlled bounds rather than completely transforming the signal. By adjusting envelope amplitudes within specific threshold ranges rather than applying extreme transformations, the masking effectiveness is improved while maintaining the overall structure and intelligibility of the original speech signal.
Data Source
AI summary
In a masking sound generating apparatus, a band divider divides a target sound signal into a plurality of frequency bands to generate a plurality of band signals. An envelope signal generating part generates a plurality of envelope signals representing respective envelopes of the plurality of the band signals. A signal converter segments each of the plurality of the envelope signals into a plurality of frames, then specifies frames of segmented envelope signals which have an amplitude greater than a first threshold and less than a second threshold, and changes an order of the specified frames in an arrangement of the plurality of the frames. A multiplier multiplies each of the plurality of the envelope signals by a noise signal, each envelope signal having the order of the frames changed by the signal converter, and outputs the plurality of the envelope signals multiplied by the noise signal as individual band masking signals. An adder adds the individual band masking signals to output a masking sound signal capable of masking the target sound signal.