Glossary

Defined Term	Definition
A-weighting	A frequency weighting devised to attempt to account for the fact that human response to sound is not equally sensitive to all frequencies. It consists of an electronic filter in a sound level meter which attempts to build this variability into the indicative sound level reading so that it will correlate, approximately, with the human response.
Ambient Sound Level, LAeq,T	The steady sound level which, over a period of time T, contains the same amount of A-weighted sound energy as the time varying sound over the same period. Also known as the equivalent continuous sound pressure level.
Attenuation	The reduction in magnitude of sound energy.
Background Sound Level, LA90,T	The A-weighted sound pressure level that is exceeded by the residual sound at the assessment location for 90% of a given time interval, T, measured using fast time-weighting, F, and quoted to the nearest whole number of decibels.
Best Practicable Means (BPM)	Adopting the best available methods to reasonably control noise and vibration.
Basic Noise Level (BNL)	A measure of traffic source noise prior to development. It is calculated from traffic flows, road speed, and Heavy Goods Vehicle percentage.
Broadband	A sound with energy distributed across a wide range of frequencies. Used to describe a single-figure sound level.
Decibel (dB)	A unit used to measure or compare the intensity of a sound by comparing it with a given reference level on a logarithmic scale.
Dimensionless	A pure number having no units attached and having a numerical value that is independent of whatever system of units may be used to derive it.
Ground factor, G	A dimensionless parameter which allows for the consideration of the acoustic properties of the ground surface between a sound source and the receptor.
Hemispherical radiation	The emission of sound throughout a hemisphere in the presence of a single reflective surface (e.g. the ground). Corresponds to a radiation loss of 8 dB.
Impulsivity	A measure of the sharpness of sudden nature of a sound which is short in duration such as a gunshot or a blast.
Intermittency	A measure of the ‘on/off’ nature of a sound source.
Landfall	The area in which the offshore export cables make landfall and is also the transitional area between the Offshore Transmission Assets and the Onshore Transmission Assets. Located in the intertidal area (see definition above) at Sinclair’s Bay.
Logarithmic averaging	A method by which sound levels in decibels (dB) can be averaged. This allows us to account for the fact that higher levels of sound will always dominate in the presence of lower sound levels.
Maximum Design Scenario	The scenario within the design envelope likely to result in the greatest impact on a particular topic receptor, and therefore the one that should be assessed for that topic receptor.
Mean High Water Springs (MHWS)	The average tidal height throughout the year of two successive high waters during those periods of 24 hours when the range of the tide is at its greatest.
Mean Low Water Springs (MLWS)	The average tidal height throughout the year of two successive low waters during those periods of 24 hours when the range of the tide is at its greatest.
Noise	An unwanted or unexpected sound.
Onshore Environmental Impact Assessment (EIA) Report (hereafter, ‘Onshore EIA Report’)	Document prepared to report the findings of the EIA for the Proposed Development and produced in accordance with the EIA Regulations. An Onshore EIA will be submitted to support the Onshore Application for the Proposed Development.
Onshore Export Cable	The cables (220/275 kV) that transfer electricity from Landfall to the Substation.
Onshore Export Cable Corridor	The area of seabed landward of MLWS to the Substation within which the Onshore Export Cables will be installed and forms part of the PPP Application Boundary.
Operation and Maintenance	The phase of the Proposed Development following completion of construction. This phase of development includes routine inspections, repairs and replacement of infrastructure and equipment and general upkeep of the Proposed Development through its operational lifespan.
Peak Particle Velocity (PPV)	An indicator of the magnitude of ground vibration which refers to the movement of molecular particles within the ground.
Planning Permission in Principle	Planning Permission in Principle is a type of planning application that allows a proposal to be assessed without having to give the details of the final layout, design or finish of any buildings. It is granted subject to a condition that certain matters have to be approved by the planning authority before the work begins. Planning permission in principle does not actually allow for development to commence, but rather that the principle of that development is accepted by the planning authority.
Porosity	The ratio of space or holes and the total volume of a material. A means of defining the ability of a material to allow sound to transmit through it.
Project (the)	An overarching term for the Ayre Offshore Wind Farm (Ayre OWF) comprising the offshore and onshore infrastructure required to generate and transmit electricity from the Array Area to the onshore Grid Connection Point (GCP). The Project includes the Offshore Generation Assets, the Offshore Transmission Assets and the Onshore Transmission Assets.
Proposed Development	Term used to define the Onshore Infrastructure associated with the Project landward of MLWS for which PPP is being sought. Further details of the parameters are included in the Onshore EIA Report Volume 1, Chapter 3: Project Description.
Propagation	The transmission of acoustic energy through a medium via a sound wave.
Residual Sound Level	The ambient sound level at a receptor in the absence of influence from the sound source under assessment.
Sound	Fluctuations of pressure within a medium (gas, solid or fluid) within the audible range of loudness and frequencies which excite the sensation of hearing.
Sound Power Level, LW	The total sound energy emitted by a source per unit time.
Sound Pressure Level, Lp	The amount of force a sound wave exerts on a surface area perpendicular to the direction of travel. A measure of the variation of sound level over a distance.
Specific Sound Level	The equivalent continuous A-weighted sound pressure level produced by the specific noise source at the assessment location over a given reference time internal.
Spectrum	The presentation of sound in terms of the amount of energy at different frequencies.
Statutory consultee	Organisations and bodies, defined by statute, who must be consulted on relevant planning applications. Of relevance to the Proposed Development this includes NatureScot; Scottish Environment Protection Agency (SEPA); Historic Environment Scotland, and any other public body which the planning authority (The Highland Council) considers is likely to have an interest in the Proposed Development by reason of that body’s specific environmental responsibilities or local and regional competencies.
Study Area	For each environmental topic, the baseline environment will be characterised, and the potential environmental impacts will be described within a topic-specific study area. Specific study areas are defined for each topic and are based on the maximum spatial extent across which potential impacts of the Project may be experienced by the relevant receptors.
Substation	The onshore Substation to be constructed as a component of the Proposed Development. The Substation would transform voltage from low to high by means of electrical transformers to ensure the electrical energy provided from the Offshore Generation Assets is at a voltage suitable for connection to the National Grid.
Substation Switchyard	The area proposed for the Substation equipment required to transform voltage from low to high by means of electrical transformers.
Tonality	A measure of sound quality that correlates to how humans perceive certain frequencies of sound. A sound is considered tonal if the frequency spectrum contains a lot of sound energy at a single frequency.
Thistle Wind Partners (TWP)	The Joint Venture (JV) of DEME Group, Qair, and Aspiravi as the energy companies that have partnered to develop the Proposed Development.
400 kV Cables	Cables that will connect the Substation to the grid connection point which is a new substation proposed by SSEN-T known as Banniskirk Hub.
400 kV Cable Corridor	The 400 kV Cable Corridor will house the cabling required for the onward transmission from the Substation to the proposed SSEN-T substation, Banniskirk Hub.

Acronyms