Sound Insulation – The Many Methods of Sound Reduction

In simple terms, sound insulation is reducing the sound from the source (sender) getting into a room (the receptor). There are several methods on reducing the sounds coming from these extraneous sound-makers. The receptors include theaters and recording rooms among others.

Some of the methods used include increasing the distance between the sound maker and the receptor, the use of noise barriers (either through reflection or deflection of the sound waves) and the use of damping structures like baffles or the use of anti-noise sound generators.

Also usable are acoustic quieting, noise mitigation, and noise control in limiting noise. Soundproofing can suppress the unwanted indirect sound by reflection that can cause echoes and resonances.

Methods

One way of reducing the transmission of unwanted sound is sound proofing by way of using distance and intervening objects in the sound’s path. The density of the sound decreases as it spreads out. With distance, the intensity of the sound waves becomes less and less.

Damping reduces the resonance of sound in a room by absorption or re-direction. The methods are reflection and diffusion. Absorption reduces the sound level while re-direction makes unwanted sound harmless by reducing its coherence.

During the absorption of sound, parts of the sound energy are converted into heat in the intervening object (the one that absorbs it) rather than the sound is being transmitted or reflected. The absorbing material for sound is determined by the frequency distribution of the noise.

Absorbers

An open cell rubber foam or melamine sponges absorb sound by friction within their cell structures. Throughout the broad range (medium) of frequencies, the porous open cell foams are highly effective sound absorbers.

These cell foams can absorb sound depending on the cell size, porosity, material thickness and material density, including tortuosity. The other sound absorbers include resonant panels.

The reflectors will make the sound hitting them be reflected than if the sound hits a softer medium like fiberglass. (It is used to deflect sound skyward in noisy highways caused by speeding vehicles.)

Transfers

The transfer of sound from a room into the outside happens thought mechanical ways. The vibration passes directly through the brick, woodwork and other solid structural elements. When the sound meets other elements like a wall, ceiling, floor or window (all these can act as sounding boards), the sound is amplified and heard in the second space (the outside).

Mechanical transmissions are faster and more efficient and can be readily amplified than an airborne transmission (sound released on its own) of the same initial strength. Soundproofing with the use of acoustic foam and other absorbent materials is less effective, in this case.

Another method of sound proofing is simply breaking the connection between the room that contains the sound source and the outside space. (It is called acoustic de-coupling.) This eliminates the vibration transfer in solid and in the air.

Sound insulation takes in many forms and the use of some devices. The main purpose is to break the vibrations transfer from one medium to the other (solids to air, air to solids, and solid to solid materials).