AIRBORNE SOUND
STRUCTURE BORNE SOUND
Airborne sound originates in a space with any sound producing source and although it changes to structure-borne sound when the sound wave strikes the room boundaries it is still referred to as airborne because it originates in the air.
Structure sound is generally understood as energy delivered by a vibrating or impacting source directly contacting the structure.
Hence a child crying in an adjoining apartment is contributing to airborne sound but the same child bouncing a ball on the floor is creating structure-borne sound,in this case by impact.
DISTINCTION BETWEEN AIRBORNE AND SRUCTURE-BORNE SOUND
All sound transmission is both airborne and structure-borne since,once having entered the structure,the sound travels along the structure and causes the structure to vibrate,in turn generating airborne sound.
Airborne sound is generally much less disturbing than structure borne, since its initial energy is very small and it decreases rapidly at boundaries.Structure borne sound is generally at a much higher energy level initially and decreases slowly as it travels through the structure,thereby creating disturbance over large sections of a building.
PRINCIPLES OF NOISE REDUCTION
Reduction of noise generation at the source by proper selection and installation of equipments.
Reduction of noise transmission from point to point by proper selection of construction materials and appropriate construction techniques.
Reduction of noise at receiver through acoustical treatment of the relevant spaces.
DIFFERENT AIRBORNE-SOUNDS
AIRBORNE SOUND AND RIGIDITY OF A BARRIER
Rigidity of the barrier can be similar to that of a drumhead – the tighter it is stretched,the better it resounds.
Rigidity in a panel barrier resists damping and assists vibrations,making it good transmitter and conversely a poor noise transmission insulator.
If,however, a barrier is constructed of 2 separate layers without rigid interconnection,its performance is always better than normal barrier.
Performance can be further improved by filling the void with porous,sound absorbent material.
CONSTRUCTION TECHNIQUES TO AVOID FLANKING PATHS
DOORS IN WALL
Doors and windows can in large measure determine the overall transmission loss of a wall.
Since in almost every instance doors and windows have a lower acoustic transmission loss than that of the wall they are mounted,particular care to be taken not to further degrade performance with air leaks.
Louvered doors are useless as sound barriers.
The most important step in sound proofing doors is complete sealing around the opening.Door in closed position should exert pressure on these gaskets making joints airtight.
SPEECH PRIVACY IN OFFICE DESIGN
It has been demonstrated by numerous studies that productivity and noise are related inversely,when the noise is information bearing.
When the noise does not carry information,it can be annoying and therefore counterproductive or it can be useful as a masking sound,depending on its frequency content,intensity level and constancy.
IMPACT OF STRUCTURE BORNE SOUND
HIGH INTENSITY SOUND INTRODUCED BECAUSE OF ABSENCE OF AIR CUSHION.
SOUND TRAVELS WITH MIN. ATTENTUATION & GREAT SPEED
SOUND ATTENTUATED ONLY BY DISCONTINUITIES IN THE STRUCTURE.
PARTIAL SOLUTIONS ARE NOT USEFUL, ENTIRE STRUCTURE MUST BE SOUND PROOFED
ADDITIONAL MASS DOES NOT SOLVE PROBLEM OF STRUCTURE BORNE SOUND,
CONTROL OF IMPACT NOISE
CUSHION THE IMPACT
THE RESILIENT MATERIALS COMMONLY USED ARE-RUBBER FLOOR TILES AND CORK
FLOAT THE FLOOR
ISOLATION IS THE IS THE KEY TO ELIMINATE THE STUCTURE-BORNE SOUND I.e. SEPERATING THE IMPACTED FLOOR
SUSPEND THE CEILING
THANK YOU....
