Introduction

Introduction
Airborne sound waves, generated in the air (speech, music), cause a structure to vibrate and therefore to emit sound from the one side to the other. Sound insulation describes the reduction of sound because of the separating material. It is an important material property and it can either be measured in a laboratory or theoretically in real life situation.There is no data available about the sound properties of papercrete so I will theoretically predict its behavior.I will first calculate the acoustic properties of a block  with two holes  for plumping,wiring, or reinforcement and compare it with different blocks.

Block 02
Block 02 has no sand in the mix. The sound properties cannot be calculated as a homogeneous material because of the holes for plumping, wiring or wall reinforcement.
I divided the block in 5 pieces.
– P1, P3 and P5 will behave as homogeneous solid material and its acoustic behavior will be similar to the mass law of homogeneous walls
– P2, P4 will behave as cavity walls
Mass law

P2, P4: Cavity wall behavior

Combined graph

Compare blocks
With the same process I calculated and made diagrams with the sound insulation properties of other blocks. I wanted to compare and check how Block 02 can improve its behavior.
First I calculated the R-value for a homogeneous block of the same size, which proved to have the worst properties -even if the coincidence effect occur even in lower frequencies.Joining the two cavities in one, I managed to improve the sound insulation properties and create a lighter and cheaper block because we reduce the material used.Finally, in block 04, I added sand in the mix improving even more the sound behavior, Adding sand in the mix -block 04- improve the sound insulation properties of the block by increasing the weight and the mass.
Block 04 has mass>70 in the homogeneous part. That has both positive and negative effects. The sound insulation values are increased however, f1 and fg shift to the right closer to the voice range frequency (but still out of it). Sand, increases the acoustic behavior of the block but results in a block almost 2 times heavier that the BetR-blok®.

Compare different blocks

Two issues that need further investigation are the possible leaks and the influence of a sound abortion inside the cavity.Gaps and cracks have negative influence in the total sound insulation of a structure. Rigid connections are needed to avoid reduction. Coupling between leafs and flanking sound transmission can also reduce the sound insulation of a cavity construction, and must taken seriously into concern.
Sound insulation material reduce the drop on mass spring resonance and dampen the standing waves. When resonance occurs in a cavity, the modeluces of air make large excursions around their equilibrium position. These excursions are limited by adding a material which can absorb the sound (glass wool, synthetic foams). Insulation material technology has advanced and we now know but it also increase the cost and decrease the sustainability of the material.


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About Menelaos Kokkinos

Menelaos Kokkinos TU Delft mgkokkinos@gmail.com
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