Planning Consultation Guidance Notes
Appendix 2
When considering the potential impact of a proposal for an entertainment venue or new residential development near an entertainment venue, consultants should consider the overall noise level (LAeq) and the 63 Hz and 125 Hz octave band noise levels (Leq). Music in the 63 Hz and 125 Hz octave bands, often described as 'bass noise', is particularly difficult to contain and the impulsive and non-steady character of low frequency music noise is particularly disturbing for local residents exposed to it.
Existing noise standards/criteria are not appropriate for evaluating low frequency noise; in almost all other situations the established noise descriptors are based on the A-weighted sound level (dBA), which effectively filters out low frequency sounds (Moorhouse et al. 2011). When dealing with noise control, especially at the lower frequencies, it is usual to look at the octave band data as a Z-weighting (linear) and not the A-weighting, due in main to the amount you have to 'take off', resulting in meaningless data (-26.2dB at 63Hz), and also with respect to the sound insulation performance of various constructions materials.
Rather than just A-weighted levels being assessed, e.g. internal noise levels as per BS 8233: 2014, a low frequency band analysis should be carried out (McCullough et al. 2004).
In the 'Procedure for the assessment of low frequency noise complaints (NANR45)-Revision 1', Moorhouse et al. (2011) use limits for low frequency noise levels in 1/3 octave bands between 10Hz and 160Hz.
For the assessment of low frequency music noise, it is more practical to consider the 63 Hz and 125 Hz octave bands. The Noise Council's Code of Practice (1995) on 'Environmental Noise Control at Concerts' suggests limits on both these octave bands.
The DEFRA report 'Noise from Pubs and Clubs-Phase 1' suggests limits on 1/3 octave bands. However, the problem with this suggestion, and one of the reasons it is not widely used, is due to the difficulty in obtaining 1/3 octave band sound insulation performance data for various construction materials.
With regards to assessing music noise, the 63 Hz and 125 Hz octave band levels as shown in Figure 2 have been plotted against the NR 15 curve as shown in Figure 3,and a good correlation at low frequencies is evident (the octave bands were calculated from the 'Moorhouse curve' by logarithmically adding the adjacent 1/3 octave bands).
However, the NR curve may be too stringent at mid and higher frequencies and may be lower than background noise levels in habitable spaces. Furthermore, the NR curve is most commonly used to set limits for mechanical services noise in buildings,i.e. steady, continuous noise sources. Music noise has different characteristics and as such can be described as unsteady and non-continuous in comparison.
Even though the Moorhouse curve does not specifically relate to entertainment noise (as per the caveat in the revised edition) these levels provide a good practical basis to assess low frequency music noise. They also provide a workable prediction for planning applications and a measurement method and assessment for in-situ low frequency issues in existing habitable spaces.