Attachment 5 - Environmental Noise Assessment

RMS
The root mean square level is used to represent the average level of a wave form such as vibration.
Satisfactory Design Sound Level
Satisfactory Design Sound Level refers to the level of noise that has been found to be acceptable for
the environment in question, which is also to be non-intrusive.
Sound Pressure Level (Lp)
Sound Pressure Level refers to a noise source which is dependent upon surroundings, and is
influenced by meteorological conditions, topography, ground absorption; distance etc. Sound
Pressure Level is what the human ear actually hears. Noise modelling predicts the sound pressure
level from the sound power levels whilst taking into account the effect of relevant factors
(meteorological conditions, topography, ground absorption; distance etc).
Sound Power Level (Lw)
A sound power level of a noise source cannot be directly measured using a sound level meter. It is
calculated based on measured sound pressure levels at recognised distances. Noise modelling
includes source sound power levels as part of the input data.
Specific Noise
Specific Noise relates to the component of the ambient noise of interest. It can be specified as the
noise of interest or the noise of concern.
Tonal Noise
A tonal noise source can be designated as a source that has a specific noise emission over one or
several frequencies, such as droning. The quantitative definition of tonality is:
the presence in the noise emission of tonal characteristics where the difference between —
    a) the A-weighted sound pressure level in any one-third octave band; and
    b) the arithmetic average of the A-weighted sound pressure levels in the 2 adjacent one-third
       octave bands, is greater than 3 dB when the sound pressure levels are determined as LAeq,T
       levels where the time period T is greater than 10% of the representative assessment period,
       or greater than 8 dB at any time when the sound pressure levels are determined as LA Slow
       levels.




Ref: 21030929 - 01a                                                                       Page 23 of 24