Definitions. All acoustical terminology shall be that contained in
ANSI S1.1, "Acoustical Terminology," and as follows:
A-WEIGHTED SOUND LEVEL
The sound pressure level in decibels, as measured with a
sound level meter, using the A-weighted network. A level so read is
designed db(A) or dBA.
AMBIENT NOISE
The all-encompassing noise associated with a given environment,
being usually a composite of sounds from many sources, near and far.
AMPLITUDE
The absolute value of the maximum displacement from zero
value during one period of oscillation.
ANSI
American National Standards Institute or its successor bodies.
CONSTRUCTION
Any safe preparation, assembly, erection, substantial repair,
alteration, or similar action, but excluding demolition, for or of
public or private rights-of-way, structures, utilities or similar
property.
CYCLE
A complete sequence of values of a periodic quantity that
occur during a period.
DAY
The hours between 7:00 a.m. and 10:00 p.m.
DECIBEL
A standard unit of measuring sound pressure levels that is
equal to 1/10 of a bel and is a unit of level when the base of the
logarithm is the tenth root of 10, and the quantities concerned are
proportional to power; abbreviated "dB."
DEMOLITION
Any dismantling, intentional destruction, or removal of structures,
utilities, public or private right-of-way surfaces, or similar property.
EMERGENCY
Any occurrence or set of circumstances involving actual or
imminent physical trauma or property damage which demands immediate
action.
EMERGENCY WORK
Any work performed for the purpose of preventing or alleviating
the physical trauma or property damage threatened or caused by an
emergency.
FLUCTUATING SOUND
A sound whose sound pressure level varies significantly but
does not equal the ambient environmental level more than once during
the period of observation.
FREQUENCY
The reciprocal of the primitive period of a function periodic
in time. The unit is the cycle per unit time and must be specified;
typically this unit will be Hertz (Hz), i.e., cycles per second.
IMPULSIVE SOUND
An impulsive sound is characterized by brief excursions of
sound pressure (acoustic impulses) which significantly exceed the
ambient environmental sound pressure. The duration of a single impulse
is usually less than one second.
INTERMITTENT SOUND
A sound whose sound pressure level equals the ambient environmental
level two or more times during the period of observations. The period
of time during which the level of the sound remains at an essentially
constant value different from that of the ambient is on the order
of one second or more.
MICROBAR
A unit of pressure commonly used in acoustics that is equal
to one dyne per square centimeter.
NIGHT
The hours between 10:00 p.m. and 7:00 a.m.
NON-STEADY SOUND
A sound whose level shifts significantly during the period
of observation.
PERIOD OF OBSERVATION
The time interval during which acoustical data are obtained.
The period of observation is determined by the characteristics of
the sound being measured and should also be at least 10 times as long
as the response time of the instrumentation. The greater the variance
in indicated sound level, the longer must be the observation time
for a given expected accuracy of the measurement.
PERSON
Any person, persons, firm, association, copartnership, joint
venture, corporation, or any entity public or private in nature.
PUBLIC RIGHT-OF-WAY
Any street, avenue, boulevard, highway, sidewalk, or alley
or similar place which is owned or controlled by a governmental entity.
REAL PROPERTY BOUNDARY
An imaginary line along the ground surface and its vertical
extension which separates the real property owned by one person from
that owned by another person, but not including intra-building real
property divisions.
SOUND
An oscillation in pressure, particle displacement, particle
velocity, or other physical parameter in a medium with internal forces
that causes compression and rarefaction of that medium. The description
of sound may include any characteristic of such sound, including duration,
intensity and frequency.
SOUND ANALYZER
A device for measuring the band pressure level or pressure
spectrum level of a sound as a function of frequency.
SOUND LEVEL METER
An instrument including a microphone, an amplifier, an output
meter, and frequency weighting networks for the measurement of noise
and sound levels in a specified manner.
SOUND PRESSURE LEVEL
The sound pressure level, in decibels of sound, is 20 times
the logarithm to the base 10 of the ratio of the pressure of this
sound to the reference pressure, which reference pressure must be
explicitly stated.
SPECTRUM
A function of time and is a description of its resolution
into components, each of different frequency and usually of different
amplitude and phase and is also used to signify a continuous range
of components each of different amplitude and phase. A spectrum is
used to signify a continuous range of components usually wide in extent
within which waves have some specified characteristics such as "audio-frequency
spectrum" and is also applied to functions of variables other than
time.
STEADY SOUND
A sound whose level remains essentially constant (i.e., fluctuations
are negligibly small) during the period of observation.