Understanding sound and how soundproofing works.
What is NRC? How is NRC measured? Why is the frequency of the sound important? What is Rw or STC? How do you achieve superior speech intelligibility and speech privacy? How do you find an effective solution to various noise issues?
Megasorber’s unique 4-fold approach has all the answers you need:
How do you measure the loudness of sound? What is the “colour” of the sound?
Decibels—the loudness of noise
Decibels (dB) is a logarithmic, not a linear, unit of measurement for the loudness of sound.
Usually, a change of 1 dB is the smallest volume change detectable by the human ear. A reduction of 3 dB in noise level is equivalent to about 50% of the sound energy being removed from the system.
Regular exposure to noise at or above 85 dB causes permanent hearing damage.
Frequency – the “Colour” of noise
The “colour” or “harshness” of the noise is defined by the frequency of the sound.
The sensitivity of human hearing is frequency-dependent. Human ears are most sensitive to sound at around 1,000Hz. Human ears are less sensitive to low-frequency noise such as below 60Hz or extremely high-frequency noise such as above 10,000Hz. As a result, the noise level is adjusted to reflect the sensitivity of the human hearing and the adjusted noise level is termed dB(A), i.e., “A” weighted noise level.
Harsh noise: noise concentrating at around 1,000Hz and higher. This noise frequency tends to cause discomfort to human ears. A typical example is the high pitch noise of vacuum cleaners.
Tonal noise: when one single frequency noise is about 10dB(A) higher than all the other frequency noise. Tonal noise is extremely unpleasant especially exposed over a long period. A typical example is the “humming” noise from a transformer. Please follow this link to hear the transformer tonal noise and how to tackle the transformer noise.
Occupational Health and Safety (OHS) Requirements
Occupational Health and Safety Regulations in Victoria, Australia, limit workers’ exposure to 85 dB(A) averaged over 8 hours without wearing hearing protection.