Audio Alarm System Reducing Crest Factor for Power Efficiency
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Solution Overview
Problem
Public address systems used for alarm sounds in public buildings face challenges in meeting regulatory requirements for loudness while minimizing amplifier and loudspeaker power, as well as battery size and cost, due to high production costs and inefficiencies in existing audio signal generation methods.
Innovation Solution
An audio system that generates an alarm signal by distributing frequency components across non-overlapping critical bands, with adjustable phase relations to minimize the Crest factor, allowing for increased amplifier efficiency and reduced power consumption, while maintaining perceived loudness and compliance with regulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alarm sounds are generated using conventional public address systems to meet regulatory loudness requirements, then the alarm sounds are audible throughout the building, but the amplifier output power and loudspeaker power handling capacity increase, leading to higher system costs
Solution Approach 1:
The audio signal is segmented into multiple frequency components distributed across non-overlapping critical bands. Each component is generated separately and combined to create the alarm sound, allowing the power to be distributed across multiple frequency bands rather than concentrated in a single band, thereby reducing the power handling requirements of individual loudspeakers and amplifiers
Solution Approach 2:
The invention changes the frequency distribution parameters of the alarm sound by distributing energy across multiple non-overlapping critical bands rather than using a conventional single-frequency or narrow-band approach. This parameter change allows the same perceived loudness to be achieved with lower peak power requirements
2Reliability
If alarm sounds are generated with sufficient amplifier output power to meet loudness requirements, then the alarm sounds are audible throughout the building, but the backup battery size and cost increase
Solution Approach 1:
The alarm signal is segmented into multiple frequency components that can be generated more efficiently, reducing the total power consumption and allowing for a smaller backup battery while maintaining the required 30-minute operation on backup power
Solution Approach 2:
By changing the frequency distribution parameters to utilize non-overlapping critical bands, the system achieves the same loudness with lower RMS power consumption, directly reducing the energy storage requirements of the backup battery
3Illumination intensity
If signal components are distributed over the audible spectrum in non-overlapping critical bands to increase loudness, then the perceived loudness increases, but the device complexity increases due to multiple frequency generation and phase control requirements
Solution Approach 1:
The invention changes the frequency distribution parameters by distributing components across non-overlapping critical bands, which actually simplifies the mixing process compared to overlapping bands. The phase relations are controlled to minimize Crest factor, and this can be achieved through systematic phase adjustment rather than complex real-time control
Solution Approach 2:
The invention replaces complex mechanical or electronic mixing systems with a more efficient approach based on psychoacoustic principles. By using non-overlapping critical bands and controlling phase relations mathematically, the system avoids the need for complex analog mixing hardware
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 enhances loudness and efficiency by optimizing amplifier usage, reducing power requirements, and ensuring alarm sounds are audible amidst background noise, thereby lowering system costs and meeting regulatory standards without excessive amplifier or battery size.
Implementation Method 1
From psychoacoustics it is known that for increasing the loudness of a signal, signal components should be distributed over the audible spectrum as much as possible in non-overlapping critical bands
Implementation Method 2
the audio system comprises means for defining and/or controlling the phase relations of the components of the audio signal at the base frequency as well as at the other frequencies
Data Source
AI summary
The invention relates to an audio system for generating an audio signal. More specifically the invention relates to an audio system, especially an audio alarm system, for generating an audio signal comprising means for generating a component of the audio signal at a base frequency and means for generating further components of the audio signal at other frequencies than the base frequency, whereby the base and the other frequencies are separated from each other by separating frequency bands in order to enhance the loudness of the audio signal. The invention furthermore relates to a method for generating an audio signal, a computer program and an audio signal.