QMark: Guidelines for environmental noise assessment

Mark Dawson, technical director at Wardell Armstrong sets out the firm's approach to noise impact assessments

In October 2014 IEMA introduced new guidelines for noise impact assessment to provide specific support on how noise impact assessment fits within the EIA process.

Noise impact assessments have undergone a degree of change in recent years with the cancelling of tried and tested noise guidance by the introduction of the national planning policy framework (NPPF). Much reliance for assessing the impact of noise had previously been placed on planning policy guidance 24 from 1994, but the NPPF swept away many pages of subtly nuanced guidance which had been built on many years of experience.

Paragraph 123 of the NPPF states that ‘planning decisions should aim to avoid noise from giving rise to significant adverse impacts on health and quality of life as a result of new development’ but it leaves the definition of ‘adverse impact’ to the noise policy statement for England (NPSE).

NPSE sets out three categories of impact:

NOEL: No observed effect level.

This is the level below which no effect can be detected.

LOAEL: Lowest observed adverse effect level.

This is the level above which adverse effects can be detected.

SOAEL: Significant observed adverse effect level.

This is the level above which significant adverse effects occur.

The planning practice guidance which was introduced in 2014 to support the NPPF expands these effect levels into its noise exposure hierarchy:

Noise exposure hierarchy

Perception Examples of outcomes Increasing effect level Action Not noticeable No effect No observed effect No specific measures required Noticeable and not intrusive Noise can be heard, but does not cause any change in behaviour or attitude. Can slightly affect the acoustic character of the area but not such that there is a perceived change in the quality of life. No observed adverse effect No specific measures required Lowest observed adverse effect level Noticeable and intrusive Noise can be heard and causes small changes in behaviour and/or attitude, for example, turning up volume of television; speaking more loudly; closing windows for some of the time because of the noise. Potential for non-awakening sleep disturbance. Affects the acoustic character of the area such that there is a perceived change in the quality of life. Observed adverse effect Mitigate and reduce to a minimum Significant observed adverse effect level Noticeable and disruptive The noise causes a material change in behaviour and/or attitude, such as having to keep windows closed most of the time, avoiding certain activities during periods of intrusion. Potential for sleep disturbance resulting in difficulty in getting to sleep, premature awakening and difficulty in getting back to sleep. Quality of life diminished due to change in acoustic character of the area. Significant observed adverse effect Avoid Noticeable and very disruptive Extensive and regular changes in behaviour and/or an inability to mitigate effect of noise leading to psychological stress or physiological effects, such as regular sleep deprivation/awakening; loss of appetite, significant, medically definable harm, for example auditory and non-auditory. Unacceptable adverse effect Prevent

In the EIA process it is important to consider the significance of an environmental impact not only by the magnitude of the impact, but also by the sensitivity of the receptor. The following three tables summarise the approach we have adopted, and are offered as a means of applying planning policy and practice guidance to the EIA process.

Table 1 describes the magnitude of impact of noise. The increasing effect levels in the noise exposure hierarchy are given an equivalent subjective perception rating, which rises from ‘not noticeable’ through intermediate categories to ‘noticeable and very disruptive’. These perception ratings have been used to derive descriptors for a range of magnitudes of noise impacts. The terms ‘not noticeable’, ‘noticeable and not intrusive’, ‘noticeable and intrusive’ and ‘noticeable and disruptive’ in the noise exposure hierarchy equate to ‘negligible’, ‘small’, ‘medium’ and ‘large’ in table 1.

Table 1 magnitude of noise impact

Descriptor Description Large Impact resulting in a considerable change in baseline environmental conditions predicted either to cause statutory objectives to be significantly exceeded or to result in severe undesirable/desirable consequences on the receiving environment. Medium Impact resulting in a discernible change in baseline environmental conditions predicted either to cause statutory objectives to be marginally exceeded or to result in undesirable/desirable consequences on the receiving environment. Small Impact resulting in a discernible change in baseline environmental conditions with undesirable/desirable conditions that can be tolerated Negligible No discernible change in the baseline environmental conditions, within margins of error of measurement

Table 2: The sensitivity of the receptor

High Receptor/resource has little ability to absorb change without fundamentally altering its present character, or is of international or national importance. For example hospitals, residential care homes, and internationally and nationally designated nature conservation sites which are also known to contain noise sensitive species (noise may change breeding habits or threaten species in some other way). Medium Receptors/resource has moderate capacity to absorb change without significantly altering its present character. For example homes, offices, schools, and play areas. Locally designated nature conservation sites which are also known to contain noise sensitive species (noise may change breeding habits or threaten species in some other way). Low Receptor/resource is tolerant of change without detriment to its character or is of low or local importance, for example industrial estates. Negligible Receptor/resource is not sensitive to noise.

The significance of the impact of noise is then determined by the interaction of magnitude and sensitivity. The impact significance matrix is set out below.

Table 3 Impact significance matrix

Magnitude

Sensitivity

High Moderate Low Negligible Large Very substantial Substantial Moderate None Medium Substantial Substantial Moderate None Small Moderate Moderate Slight None Negligible / beneficial None None None None

The threshold between insignificant and significant lies between ‘moderate’ and ‘substantial’. Moderate impacts might be noticeable and intrusive but may cause a small change in behaviour. Substantial impacts might be noticeable and disruptive, and might cause a material change in behaviour or attitude.