Considering acoustics approach

User wrote in Korean, so I'll reply in that tone. The acoustics issue involves frequencies between 700-1500 Hz, vibrations, flanking paths, and decoupling strategies. I'll focus on practical solutions using mass laws for transmission loss and the effect of added layers. A small 50x50 cm patch might decrease noise marginally, but structural properties matter. The neighbor’s tactile transducer complicates things though.

Addressing noise reduction

The noise comes from the slab above, where structure-borne vibration transfers into the user’s balcony. They're looking to reduce noise using a small 50x50 cm treatment above the source. They propose layering 10mm EVA foam, butyl sheet, and a 5 cm gym mat for mass and damping, forming a "floating panel."

Evaluating vibration reduction

For structure-borne vibration through the slab, a small damped mass patch can reduce vibrational velocity and noise radiation. However, due to the large area and wave propagation, it won't have a huge effect on its own. If placed precisely above the source, the patch could offer a 3-6 dB reduction, especially around 700-1500 Hz frequencies.

Refining vibration reduction methods

Targeting the highest velocity spot directly above the source could bring a 3-6 dB noise reduction, especially at 700-1500 Hz, but the slab’s modal density may limit it to 1-3 dB spatially. A more effective approach would be breaking the structural path with increased damping, through a constrained layer (like butyl with a stiff plate), or using a tuned mass damper for broader frequency ranges. This latter method, though, would be tricky to optimize across the full range.

Optimizing noise reduction

Targeting the spot of highest velocity above the source can reduce sound by 3-6 dB, especially in the mid-high frequency range (700-1500 Hz), but a smaller patch will only yield modest results (1-3 dB). A better approach would be increasing damping with a constrained layer on the slab or using a tuned mass damper. On the receiver side, placing a limp-mass barrier decoupled from the slab could help, though a small 50x50 cm area limits its effectiveness.

Proposed balcony noise solutions

For the user’s noise concerns, options include addressing glazing gaps, using heavy curtains, or treating the ceiling. Focusing on the balcony, a mass-loaded barrier or decoupled floor tile with rubber underlay might reduce structure-borne sound. A small mass-spring-mass patch with pavers or constrained damping using butyl and a steel plate could diminish sound. Other strategies could include using a "limp-mass absorber" and sealing gaps.

Plan B for noise reduction

To tackle noise, use a phone’s SPL meter and spectrogram app like Spectroid. Try a mass-spring isolation system with dense rubber pads and concrete pavers. For added isolation, use a thick acoustic foam or rug to act as a micro-absorber. Seal gaps near the balcony door or windows and consider placing heavier items like planters on rubber pads. A feedback loop with measurements will help identify the best spot.

Thought for 49s