The Mayor's Ambient Noise Strategy - Greater London Authority

The Mayor’s Ambient Noise Strategy Mayor of London 255
Hybrid-electric vehicles Hybrid-electric drive can take several forms.
For example, a petrol engine can be used to generate electricity, with
batteries buffering peak acceleration demands. The engine, or other
power source such as fuel cells, can be smaller, and noise and vibration
can be more readily controlled. The engine can run at an optimum speed,
enabling noise control systems to be more effective.
Hyperacusis abnormal discomfort caused by sounds which are usually
tolerable to other listeners.
ILS (Instrument Landing System) see Glidepath.
Immission A measure of sound pressure at a given receptor point.
Impact sound Sound energy generated by direct impact on a building
element, such as a hard-heeled shoe on a floor.
Infra-red (hearing) systems Systems which enable deaf people wearing
a special receiver to hear specially-transmitted sounds accurately, with
good sound quality. The systems restrict sound to an individual room, and
so are appropriate for cinemas and conference centres.
Infrasound Noise at frequencies below about 20 Hz is sometimes
referred to as infrasound (see also Low frequency noise).
Insulation Sound insulation is the prevention of the transmission of
sound through a barrier such as a wall or window. There is no direct and
inherent relation between the sound insulation value of a barrier and the
sound absortion performance of its surface. ‘Impact insulation’ is typically
provided by a resilient layer, such as a carpet or foam-backed vinyl sheet
on floors.
Isolation The introduction of a discontinuity between two elements in an
energy tranmission chain. The process of isolating a specific source of
sound from existing background noise.
Integrated Pollution Prevention and Control (IPPC) A permit system
for controlling pollution from industrial activities, introduced to comply
with European Commission Directive 96/61.
Line source A sound source which can be idealised as a line in space,
such as road or rail traffic.
L max
the maximimum sound pressure level observed in any specified period.