the loudness of sound

Decibels (dB) is a logarithmic – not a linear – unit of measurement for the loudness of sound.

Normally 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 90 dB causes permanent hearing damage.

Decibel Levels of Common Sounds

ExampleTypical Noise Level dB(A)
A pin dropping, breathing10
Recording studio30
Normal conversation60
Vacuum cleaner70
Alarm clock80
Lawn mower90
Hand drill100
Chain saw110
Emergency vehicle siren115
Jack hammer120
Jet engine at takeoff140

noise “colour”

The harshness of sound

The “colour” or “harshness” of the sound is defined by the frequency of the sound. Frequency is the number of waveforms generated in one second. For example, if you hit the middle C key on a piano, the strings in the piano will vibrate back and forward around 261 times per second. Higher pitched notes have a higher frequency and lower pitched notes have a lower frequency.

The sensitivity of human hearing is frequency dependent. Human ears are most sensitive to the noise around 1,000Hz. Human ears are less sensitive to low frequency noise such as below 60Hz or extremely high frequency such as above 10,000Hz. As a result, 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 the all the other frequency noise. Tonal noise is extremely unpleasant especially exposed over long period of time. A typical example is the “humming” noise from a transformer.

Examples of Frequency Levels

ExampleFrequency Hz
Lowest note for tuba16.35
Lowest C on standard 88-key piano32.70
Lowest note for cello65.41
Lowest note for viola130.81
Middle C261.63
C in middle treble clef523.25
Approximately the highest note reproducible by the average female human voice1046.50
Highest note for flute2093
Highest note on standard 88-key piano4186
Approximately the tone that a typical CRT television emits while running16744


Industrial noise

Occupational Health and Safety Regulations in Victoria, Australia, limit workers’ exposure to 85 dB(A) averaged over 8 hours, or to any instantaneous noise in excess of 140 dB(C).

Further Information

As each project has different requirements, this information should be used as a guide only.

Please contact the Megasorber team with any specific enquiries for additional information and recommendations.

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