Automatic Volume Control Using Speech Interference Noise Bands
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Solution Overview
Problem
Existing audio systems require manual adjustments to compensate for changing ambient noise levels, which can be inconvenient and unsafe, especially in vehicles, and often overcompensate by adjusting volume for non-interfering noise frequencies and durations.
Innovation Solution
An automatic volume control system using a digital signal processor to detect and differentiate significant noise interfering with speech intelligibility by measuring the preferred speech interference level, adjusting the audio amplifier gain based on noise levels in specific frequency bands, and employing phase and amplitude correlation, fast Fourier transform, and bandpass filtering to produce a gain control signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual volume adjustments are required to compensate for changing ambient noise levels, then the listener can maintain adequate signal-to-noise ratio, but the ease of operation deteriorates and safety is compromised
Solution Approach 1:
The system automatically monitors ambient noise levels and adjusts the audio output volume without requiring manual user intervention. The noise level detector continuously measures the acoustic environment and the volume controller autonomously modifies the amplifier gain to maintain optimal signal-to-noise ratio, making the system self-regulating and eliminating the need for manual adjustments.
Solution Approach 2:
The system implements a feedback loop where the noise level detector continuously monitors the ambient acoustic environment and feeds this information to the volume controller. The controller processes the noise level signals and adjusts the amplifier gain accordingly, creating a closed-loop control system that automatically adapts to changing noise conditions to maintain adequate signal-to-noise ratio.
2Reliability
If the volume is automatically adjusted to compensate for all ambient noise, then the signal-to-noise ratio is maintained, but the device complexity increases and overcompensation occurs for non-interfering noise
Solution Approach 1:
The system applies different processing characteristics to different frequency components of the ambient noise. The noise level detector analyzes noise in specific frequency ranges, and the volume controller adjusts gain based on the spectral characteristics of the noise. This selective approach focuses control effort on frequency bands that actually interfere with the audio signal, avoiding unnecessary adjustments for non-interfering noise components.
Solution Approach 2:
The system changes the operating parameters of the volume control based on the measured noise characteristics. Instead of using a fixed gain adjustment, the volume controller dynamically modifies the amplifier gain parameter in response to varying noise levels and frequency content. This adaptive parameter adjustment allows the system to respond appropriately to different noise conditions without requiring complex intervention for every noise type.
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
The system automatically adjusts the volume to compensate only for noise that affects speech intelligibility, reducing the need for manual controls and preventing overcompensation, thus enhancing listener experience and safety by maintaining optimal signal-to-noise ratios.
Implementation Method 1
a microphone for detecting acoustic waves emanating from the one or more speakers and background noise, and in response for producing a corresponding signal
Data Source
AI summary
A microphone detects acoustic waves from speakers, or for a two-way voice communication device, a user's voice and background noise, and produces a corresponding signal; a subtractor finds the difference between the microphone signal and a desired audio signal; a transform process produces over a time period a signal corresponding to the amplitude of each frequency component of the difference signal; from the transform process a bandpass filter passes only frequency components within selected bands; a speech interference noise level calculator calculates a combination of the amplitudes of the bandpass filtered frequency components; and a solver uses the combination to produce, according to an algorithm, a signal for controlling the gain of an audio amplifier. Phase and amplitude correlation can be done prior to subtraction.