Sealed Pipe-Loaded Loudspeaker Low Frequency Response
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Solution Overview
Problem
Small portable devices face challenges in reproducing a wide range of audio content due to limited bass or low frequency response, primarily because of their small transducer size and lack of resonance cavities, which compromises the fidelity of audio playback in devices like smartphones and laptops.
Innovation Solution
A sealed pipe-loaded loudspeaker system is introduced, featuring a transmission line acoustically coupled to the transducer, which generates pipe resonances to augment low frequencies, and a digital signal processor to compensate for resonance-related attenuation, ensuring improved low-frequency response without increasing the device's outer package size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If small transducers are used in portable devices, then device size and weight are reduced, but low frequency response is limited
Solution Approach 1:
The transmission line is folded back on itself multiple times within the sealed enclosure, nesting the acoustic path within the device's internal volume. This allows a long effective pipe length (multiple feet) to be contained within a small device footprint, generating pipe resonances that augment low frequencies without increasing external device dimensions
Solution Approach 2:
The transmission line uses a three-dimensional folded path within the sealed enclosure rather than a simple linear arrangement. By utilizing the third dimension and folding the acoustic path, the system achieves long pipe resonances in a compact space, transforming the spatial arrangement to overcome the size limitation
2Reliability
If transmission line is used to augment low frequencies, then bass response is improved, but localized attenuation peaks occur
Solution Approach 1:
A digital signal processor implements feedback control by measuring the actual frequency response of the transmission line system and applying compensatory equalization. The DSP identifies localized attenuation peaks and valleys caused by pipe resonances and applies inverse filtering to smooth the overall frequency response, maintaining bass augmentation while correcting uniformity issues
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 solution enhances the low-frequency audio response by approximately 5 dB in the 300-500 Hz range, effectively improving the bass reproduction capabilities of portable devices while mitigating undesirable acoustic effects through digital signal processing.
Implementation Method 1
The length and the diameter of the transmission line are configured to generate pipe resonances that augment the very low frequencies of the audio signal
Implementation Method 2
The digital signal processor may execute an equalization and compression function to smooth any localized and peaky attenuation within a frequency response of the audio signal
Data Source
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AI summary
Embodiments are directed to a sealed pipe-loaded loudspeaker for augmenting low frequency response in a portable electronic device. A loudspeaker transducer is configured to radiate sound directly out of a forward radiation area and incidentally out of a rearward radiation area, and a sealed transmission line forming a closed pipe acoustically coupled to the transducer through which the rearward radiation propagates to produce standing waves corresponding to the dimensions of the closed pipe, wherein resonances apply a loading to a diaphragm element of the transducer to lower its resonance frequency. An acoustical wave front radiates away from the diaphragm element for the direct sound and is emitted outside of the device, and the rearward radiation is not emitted from the device.