J Acoustic Report · 132007.2398

                                                                                           ACOUSTICS & AIR QUALITY

Appendix A Glossary


 Parameter or                                        Description
     Term
     dB           The decibel (dB) is the unit measure of sound. Most noises occur in a range of
                  20 dB (quiet rural area at night) to 120 dB (nightclub dance floor or concert).
     dBA          Noise levels are most commonly expressed in terms of the ‘A' weighted decibel
                  scale, dBA. This scale closely approximates the response of the human ear,
                  thus providing a measure of the subjective loudness of noise and enabling the
                  intensity of noises with different frequency characteristics (e.g. pitch and tone)
                  to be compared.
     Day          The period between 7am and 6pm.
   Evening        The period between 6pm and 10pm.
    Night         The period between 10pm and 7am.
  Free-field      The description of a noise receiver or source location which is away from any
                  significantly reflective objects (e.g. buildings, walls).
     L1           The noise level exceeded for 1% of the measurement period.
     L10          The noise level exceeded for 10% of the measurement period. It is sometimes
                  referred to as the average maximum noise level.
     L90          The noise level exceeded for 90% of the measurement period. This is
                  commonly referred to as the background noise level.
     Leq          The equivalent continuous sound level, which is the constant sound level over
                  a given time period, which is equivalent in total sound energy to the time-
                  varying sound level, measured over the same time period.
  Leq,1hour       As for Leq except the measurement intervals are defined as 1 hour duration.
      Lmax        Maximum A-weighted sound pressure level.
 Leq(24 hour)     The average Leq noise level over the 24-hour period from midnight to midnight.
 L10(18 hour)     The arithmetic average of the one-hour L10 values between 6am and midnight.
                  This parameter is used in the assessment of road traffic noise.
      Rw          Weighted Sound Reduction Index – is a single number evaluation of the
                  property of a partition to attenuate sounds. For the majority of partitions, the
                  value of Rw will be similar to the value for STC. Partitions with particularly poor
                  performance at 100 Hz may have lower values for Rw than for STC.
                  Conversely, partitions with poor performance at 4000 Hz may have higher Rw
                  than for STC. (As per AS1276.1-1999).




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