Glass and acoustic insulation

Sound, the auditory sensation

Sound is a wave caused by a vibration that propagates through air or other media. It is characterised by:

• its intensity (in dB) — the strength of the sound
• its frequency (in Hz) — high or low pitched
• its duration in time.

The human ear is sensitive to frequencies between 20 and 20,000 Hz.

The decibel scale

The decibel (dB) is the unit used to measure the intensity of sound. The scale is logarithmic; a doubling of sound energy corresponds to an increase of about 3 dB.

• 0 dB — auditory threshold
• 30 dB — bedroom at night
• 60 dB — normal conversation
• 80 dB — busy road
• 110 dB — pneumatic drill
• 120 dB — pain threshold

Acoustic regulation of buildings

Buildings should be designed and constructed so as to provide reasonable acoustic conditions for occupants. National building regulations set minimum standards for sound insulation of building elements.

The acoustic insulation of glazing

The sound insulation of glazing depends on several factors:

• the thickness of the glass — heavier glass is more effective
• the use of asymmetric double-glazing — combining glass of different thicknesses dampens different frequencies
• the cavity dimension and the presence of gas filling
• the use of laminated glass with acoustic interlayers — provides significant gains across the frequency spectrum.

Acoustic glass

Specialised acoustic glass typically comprises a laminated pane with a high-performance acoustic PVB interlayer. When combined within an insulating glass unit, this can achieve weighted sound reduction indices (Rw) above 40 dB.