What External Acoustic Structures Can Increase Sound Pressure Level?
Helmholtz resonator can increase the sound pressure level at a specific frequency. Sound enters the acoustic cavity through a narrow tube and is then amplified by resonance.
This is similar to the operating principle of a horn speaker, in which sound is concentrated and reflected within a narrow passage before radiating outward through a wider opening.
Another structure is the quarter-wavelength tube resonator. When the tube length is one-quarter of the target wavelength, sound at the corresponding frequency is amplified by resonance.
Based on the principles described above, some examples of sound-amplifying structures used in everyday applications are shown below:
The structure shown above gradually expands from a narrow opening to a wider opening.
The acoustic cavity shown above has a curved shape, which is not only aesthetically pleasing but also helps preserve the circular wavefront without causing significant interference.
The structure shown above amplifies sound using the operating principle of a horn speaker.