PRO AUDIO - AUDIOVISUAL - CCTV - SYSTEMS INTEGRATION

• Environmental Noise Assessment - Feature on Wind Turbines

• Industrial Noise Assessment - feature on New builds and extensions
  

• Noise Nuisance - feature on Music Noise

In Northern Ireland a planning application for a wind turbine will not require a noise assessment where it can be shown that the noise from the proposed turbine will not exceed 35 dB LA90 at the boundary of the nearest noise sensitive receiver, at any wind speed from cut in to 12 m/s. Typically this will require a separation distance of 340 metres based on a typical 250 kW turbine with a hub height of 30 m and a sound power of 97 dB.

If the projected noise from the turbine exceeds the 35 dB criterion then it may be possible to obtain planning permission if the noise from the turbine is less than the prevailing background noise + 5 dB.  The prevailing background noise can only be ascertained by measurement using the methodology of ETSU R 97.  We use a two week period of continuous measurement to obtain the prevailing background curve.  Higher background noise levels are associated with roads, rivers and forests, so you tend to find that separation distances decrease due to the proximity of these features.  Higher background noise levels have the effect of masking the turbine noise.

The prevailing background noise is established by correlating noise levels and wind speeds for the duration of the measurement period.

In practical terms this means erecting an anemometer at the turbine site and a noise analyser at the boundary of the nearest residence.  Where there is more than one neighbouring property involved, noise measurements will be needed at each property which in turn means a 2 week measurement at each property.  You should ask your acoustic consultant to liaise with Environmental Health to determine the number of properties that will require assessment.

Many applicants have their own anemometer and if it is suitable we can take data from that device and import it into our analysis.

Where the noise level from the turbine exceeds the prevailing background + 5dB then planning permission would normally be refused.  The most difficult times of the day are 6pm to 11pm Monday to Friday, 1pm to 11pm on Saturdays and all day on Sunday.  At these times of day noise levels have diminished and people are more likely to be using their gardens for recreation so that the noise from a turbine could be potentially disturbing.

The night time criterion is 43 dB which is not usually a problem as people are asleep.

A lesser standard applies where a neighbouring property is in the control of the applicant, or the occupant of the neighbouring property has a financial interest in the turbine.

Building a new industrial unit or extending existing industrial premises will frequently require a noise assessment. If the proposed building is close to residential properties BS4142 is used to assess the likelihood of complaints. BS4142 examines the noise from the industrial premises (either measured or calculated) and compares it to the background noise at the nearest noise sensitive receiver. A penalty of + 5dB is often added to the value of the industrial noise to obtain a rating value. The penalty applies where the noise comprises bangs, thumps, whistles, tones or other intermittent noise.) Where noises are impulsive or intermittent it is possible that the equivalent noise level over the reference period of 1 hour (daytime) will lower the rating value. A similar procedure is used for night time assessment with a reference time interval of 5 minutes.

At the end of the procedure the result or rated value is compared to the background noise. Where the rated value is 10 dB or more above the background level the likelihood of complaints is high. Where the rated noise level is no more than 5 dB above the background level the likelihood of complaints is marginal. Where the rated noise level is 10 dB or more below the background level the likelihood of complaints is regarded as low.

If the result was a high likelihood of complaints then mitigation measures to reduce the noise level can be examined and the procedure re-run.

In practical terms noise level measurements are required in the immediate area of the nearest noise sensitive receptors to determine the average and background noise levels. Sample measurements are carried out covering the entire period of operation during the day and night.

In Northern Ireland the requirement for music noise impacting on nearby residents is that the music noise should not exceed the NR15 reference curve at any frequency in a bedroom at night. The NR15 standard is very quiet. Most problems arise at low frequencies. The insulation value of a wall is much lower at low frequencies than it is at high frequencies. The same principle applies to the roof, doors, windows etc. This means that low frequency noise leaks out more easily, affecting nearby residents.

If you are a venue owner:

The simplest and most effective method of reducing music noise nuisance is to turn down the volume. Less volume inside, means less volume outside.  Normally this will achieve the required result.  In those cases where the music volume has already been turned down then you will need to look at the fabric of the building and how noise can be more effectively contained within the building envelope.  It is possible to link noise controllers and pre-amplifiers in the sound system signal chain to doors, windows etc.  When a door is opened the system automatically turns down the sound level.  Sound limiters can be attached ensuring that sound levels cannot exceed pre-determined values.  There are a great variety of possible solutions and we can help you understand which would be the best solution for your venue.

If you are affected by music noise:

We can help you understand what is happening and how you might deal with the problems you are having.  This may mean putting noise monitoring equipment in your home and preparing a report which will establish the actual value of noise you are subjected to.  This can then be offered to Environmental Health or the Courts as part of your complaint.