Direct Digital Speaker Filtering for Flat Volume Response
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Solution Overview
Problem
Direct digital speakers (DDS) face challenges in volume control due to their inherent frequency response characteristics, which differ from those of analog speakers, leading to non-flat sound pressure levels across frequency ranges.
Innovation Solution
A system with a direct digital speaker volume control device that includes multiple filters with distinct cutoff frequencies, allowing for selective filtering based on desired volume and frequency to generate a filtered signal for the speaker, ensuring a flat frequency response across the entire designated range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct digital speakers operate without digital to analog converter, then device complexity is reduced, but frequency response becomes non-flat across frequency ranges
Solution Approach 1:
The patent divides the audio frequency spectrum into multiple bands using separate filters (e.g., low-pass, band-pass, high-pass filters). Each filter processes a specific frequency range independently, allowing precise control over the non-flat frequency response characteristics of DDS without requiring complex global equalization circuits.
Solution Approach 2:
The patent applies different filtering characteristics to different frequency bands. Each filter is optimized for its specific frequency range, with distinct cutoff frequencies and attenuation slopes tailored to compensate for the DDS's inherent frequency response variations in that particular band, achieving localized frequency response correction.
2Use of energy by moving object
If volume control is implemented in direct digital speakers, then sound pressure level is adjustable, but frequency response flatness deteriorates
Solution Approach 1:
The patent implements dynamically adjustable filters where cutoff frequencies and attenuation characteristics can be changed in real-time based on the desired volume level. As volume increases or decreases, the filter parameters adapt to maintain a flat frequency response across the entire audio spectrum, preventing the frequency response from deteriorating with volume changes.
Solution Approach 2:
The system incorporates feedback mechanisms that monitor the actual frequency response at different volume levels and automatically adjust filter parameters to compensate for deviations. This closed-loop control ensures that volume adjustment does not compromise frequency response flatness.
Data Source
AI summary
A system that includes a direct digital speaker volume control device configured to be coupled to a direct digital speaker. The direct digital speaker includes many pressure producing elements being adapted to generate a sound at a sound pressure level (SPL) and at a given frequency in response to an input signal, without using digital to analog converter. The direct digital speaker inherently exhibits a frequency response throughout its entire frequency range. The direct digital speaker volume control device includes a module for providing few filters each having a distinct cutoff frequency such that each filter exhibits no attenuation below its cutoff frequency and an attenuation response above the filter's cutoff frequency. And a selector for selecting one of the filters according to a selection criterion that depends on a desired volume and frequency of generated sound, and applying the filter to the input signal for generating a filtered signal that fed to the speaker.