Understanding Sound

The article below provides an understanding of sound by outlining:

• the difference between impact and airborne sound
• potential soundproofing solutions
• measuring decibels (db)

Understanding sound, what it is and how it affects us? Sound is generated by air particles vibrating due to a noise source causing vibration through the air forming waves of air pressure. The ear then picks up these waves of air pressure and turns them into the sounds we hear. Sound waves are a form of energy that transmit through the air passing through surfaces like walls, floors and ceilings if they are not constructed with enough mass or separation to absorb this energy. To successfully soundproof these structures, you need to incorporate mass and separation into the buildings structure.

Sound Transmission

Sound transmitting from the source, through the air into the human ear.

Understanding the Difference Between Impact and Airborne Sound

Airborne Sound – Sound transmitting through the air from the source, talking, shouting, music, TV and barking dogs are examples of airborne sounds. Airborne sounds can transmit through a building if the separating structures do not have enough mass, through holes, and because of a lack of separation in the construction.

Impact Sound – Sound transmitting through a buildings structure from footfall, children running, furniture being moved would be classed as impact sound. Energy created through impact will vibrate through a buildings structure into other parts of the building, this will happen due to a lack of separation in the buildings structures.

Soundproofing Solutions

To successfully reduce airborne and impact noise you will normally have to combine products to achieve the maximum level of soundproofing. Airborne sound can be reduced by increasing mass of the structure, increasing the separation as well will improve the overall level of noise reduction. Impact sound through a floor can be reduced by de-coupling the ceiling below, creating separation in the ceilings structure. If you have access to the floor above a resilient layer can be laid onto the floors to absorb the impact at the source.

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Understanding Sound through Decibels (dB)

The decibel (abbreviated dB) is the unit used to measure the intensity of a sound. The decibel scale is a little odd because the human ear is incredibly sensitive. Your ears can hear everything from your fingertip brushing lightly over your skin to a loud jet engine. In terms of power, the sound of the jet engine is about 1,000,000,000,000 times more powerful than the smallest audible sound.

A 50% reduction in the subjective loudness? This is usually taken as corresponding to about 10dB, for an average person.

On the decibel scale, the smallest audible sound (near total silence) is 0dB. A sound 10 times more powerful is 10dB. A sound 100 times more powerful than near total silence is 20dB. A sound 1,000 times more powerful than near total silence is 30dB. Here are some common sounds and their decibel ratings:

Sound Source dB Level

• Threshold of Hearing 0
• Leaves Rustling 10
• Whisper 20
• Conversation 55
• Busy Traffic 70
• Vacuum Cleaner 80
• Orchestra 95
• Rock Concert 110
• Pain Threshold 130
• Jet Take Off 140
• Perforation of Eardrum 160

Table shows estimates of dB levels; external factors can alter these figures; only use these figures as a guide to sound levels. The only way to accurately measure sound is by performing a sound test using sound recording equipment.

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