For my research, I focused on how to make hearing protection quieter without making the sound muffled. Standard foam earplugs work well for protection, but they create a terrible non-linear attenuation (uneven sound blocking). They block the high-pitched sounds (treble) much more aggressively than the low-pitched sounds (bass), resulting in that annoying, muffled "underwater" sound. This uneven blocking is the main flaw I set out to fix.
Wondering what the alternative is?
flat attenuation (equal sound blocking). This means that if the earplug reduces the sound level by 18 dB, it should reduce the bass, mid-range, and treble by that same 18 dB. The resulting sound is simply a quieter version of the original - the tonal balance (the way the music or speech is mixed) is perfectly preserved. See for yourself?
The Physics of the Acoustic Filter
The hard, plastic filter core is a meticulously engineered system of tiny air chambers and tunnels. I designed these chambers to act as Helmholtz resonators (air cavities that vibrate at a specific pitch).
You can think of a Helmholtz resonator like blowing across the top of a soda bottle - it produces a specific tone based on the bottle's volume. In my research, I created multiple, highly specific micro-chambers within the filter. These chambers introduce subtle, targeted resonance (vibration) at certain frequencies to counteract the natural muffling caused by the main silicone eartip. They essentially provide the small boost needed at high-muffled frequencies to "flatten" the entire attenuation curve (the graph of how much sound is blocked).
2. Controlling the Volume with Acoustic Resistance
The small tunnels sound has to travel through are the second critical component. These tunnels create a lot of acoustic resistance (friction for the sound waves), which is the primary mechanism for reducing the overall volume of the earplugs
As sound waves are forced through these narrow, high-resistance channels, some of the sound's acoustic energy (power) is lost - it dissipates as heat. This process is called damping (absorbing energy). By precisely controlling the width, length, and materials of these tunnels, I can set the exact level of uniform attenuation (e.g., exactly 18 dB of sound reduction) that is applied evenly across the entire audible spectrum.
The System: Tip Plus Filter
Crucially, the filter doesn't work alone. It relies on a perfect seal created by the surrounding soft silicone eartip. The soft tip does the hard work of physically blocking the majority of the sound and preventing noise from leaking in, especially the low-frequency sounds that can vibrate through the soft tissues of the ear canal.
The final high-fidelity (clear, non-muffled) result is a sophisticated interaction: the eartip provides the bulk reduction, and the acoustic filter provides the precise, frequency-dependent tuning to make that reduction tonally balanced.
See How it Works for Yourself
