Directional Loudspeaker Using Horn and Interference Across Frequencies
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Solution Overview
Problem
Existing directional loudspeakers face challenges in maintaining directivity at both higher and lower frequencies, particularly due to the variation in sound wave wavelengths, which makes it difficult to achieve directional effect over a wide frequency range.
Innovation Solution
A loudspeaker design incorporating an acoustic horn for higher frequencies and destructive interference between front and rear waves around an attenuation axis for lower frequencies, utilizing phase shift and acoustically resistive materials to achieve directional effect across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bundling is used to achieve directional effect, then directional effect is obtained at higher frequencies, but the loudspeaker becomes very large at lower frequencies due to increased wavelength
Solution Approach 1:
The patent divides the frequency range into two segments: higher frequencies (second frequency range) handled by horn effect for directionality, and lower frequencies (third frequency range) handled by destructive interference between front and rear waves. This segmentation allows each mechanism to operate optimally in its respective frequency band, avoiding the need for a large loudspeaker design that would be required if bundling were used across all frequencies.
Solution Approach 2:
The patent changes the operating parameters by introducing phase shift between front and rear waves for destructive interference at lower frequencies, and using horn geometry for directional effect at higher frequencies. This parameter change allows the loudspeaker to achieve directionality without increasing physical size, as the wavelength-related constraints are overcome through controlled phase relationships and acoustic impedance management.
2Ease of manufacture
If damping is optimized on the rear side to obtain more than 15 dB of damping, then good directivity is achieved in the midfrequency range, but directivity is difficult to maintain in higher frequencies when greater reproduction range is desired
Solution Approach 1:
The patent makes the directional control mechanism dynamic by switching between two different methods based on frequency: horn effect for higher frequencies and destructive interference for lower frequencies. This dynamic adaptation allows the loudspeaker to maintain good directivity across a broader frequency range, overcoming the limitation of fixed damping optimization that only works well in the midfrequency range.
Solution Approach 2:
The patent creates a multi-functional system where the same loudspeaker structure performs different directional control functions for different frequency ranges. The horn provides directional effect for higher frequencies, while the destructive interference mechanism provides directional effect for lower frequencies, making the system universally applicable across the audio spectrum rather than limited to a single frequency band.
3Use of energy by moving object
If horn effect is used for directional effect at higher frequencies, then sound efficiency is improved, but directivity cannot be maintained at lower frequencies where wavelength becomes greater than the emitter dimension
Solution Approach 1:
The patent introduces destructive interference between front and rear waves as an intermediary mechanism to achieve directionality at lower frequencies where the horn effect becomes ineffective. This intermediary approach allows the loudspeaker to maintain sound efficiency while achieving directionality in the frequency range where wavelength exceeds the emitter dimension, overcoming the fundamental limitation of horn-based directional control.
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 design achieves improved directivity over a wide frequency range by combining horn effect for higher frequencies and destructive interference for lower frequencies, enhancing sound efficiency and reducing undesirable reflections.
Implementation Method 1
an acoustic horn which extends between a neck and a mouth along a horn axis, which neck is acoustically coupled to the front waves and which horn has a directional effect along the main axis for front waves lying in a second frequency range
Implementation Method 2
by means of a phase shift between the respective rear waves and front waves obtained by means of a difference between a rear propagation time to the attenuation axis for rear waves and a front propagation time to the attenuation axis for front waves, a directional effect along the main axis for front waves with a frequency in the third frequency range by destructive interference between the respective rear waves and front waves around the attenuation axis
Implementation Method 3
utilizing phase shift and acoustically resistive materials to achieve directional effect across a wide frequency range
Data Source
AI summary
A loudspeaker with directional effect along a main axis extending from a front side of the loudspeaker, including a housing; at least one sound source configured to produce sound waves substantially in a first frequency range, wherein the sound waves include front waves on the front side of the sound source and include rear waves on the rear side of the sound source, and an acoustic horn having a neck acoustically coupled to the front waves and a directional effect along the main axis for front waves lying in a second frequency range, and an attenuation axis lying at an angle relative to the main axis, wherein the loudspeaker obtains for front and rear waves lying in a third frequency range a directional effect along the main axis for front waves in the third frequency range by destructive interference between the respective rear and front waves around the attenuation axis.