Basics of Sound Insulation and Attenuation

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Sound Attenuation vs Insulation

Situation	Difference	Equation
Sound Attenutation	Source and receiver are within the same volume
Sound Insulation	Source and receiver are within different enclosures
Standardized Sound Insulation	Sound level difference to which a weighting term taking into account the reverberation time T of the room, as compared to a reference reverberation time T_0. Most commonly requirements books and regulations.

Sound Reduction Index (R)

Sound reduction index is the acoustic characteristic of a wall or floor for sound reduction purposes.

• R is independent of the room and envelope characteristics
• R is determined through lab measurements
• Under specific condition, R can be computed (predicted) with limited accuracy

Sound Transmission Paths

1. Direct transmission.
2. Flanking transmissions through the various constructive elements linked to the separating wall.Such flanking uses coupling coefficients, . (ISO 12354)
3. Leakage around some construction elements.
4. Secondary transmissions by means of duct layouts.

Figure 1: Acoustic transmission paths between spaces [1]

Common Sound Insulation Ranges and Values

Situation	Range (dB)	Remarks
Between offices with removable partitions	25-35	30 dB is considered by several standards for two of the same kind of activities to be carried out in two adjacent rooms.
Between doctor office and waiting room	40-50	45 dB is considered by several standards to be the minimum sound insulation value required to allow privacy between two adjacent rooms.
Between modern dwellings	50-55	Usually is the range required by most regulations.
Between cinema theatres	65-70	Usually is the range required by the background noise levels targeted by the standards of the industry.

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References

[1] M. Asselineau, Building Acoustics. Boca Raton, Florida: CRC Press, 2015.

[2] D. A. Bies, C. H. Hansen, and C. Q. Howard, Engineering Noise Control, 5th ed. Boca Raton, Florida: CRC Press, 2017.