Sabin
Sabine
Sabine Absorption
Sabine Absorption Coefficient
Sabine Reverberation Time Equation
Sampling Frequency the rate at which a continuous waveform is digitised, given in Hz.
As opposed to a vector quantity which has both magnitude and direction, for example acceleration, force and velocity
Scalar Quantities may be added, subtracted or multiplied like ordinary numbers, vector quantities can not.
EDT : Early Decay Time based on the impulse decay curve, 0 dB to -10 dB
T10 decay time based on the impulse decay curve, -5 dB to -15 dB
T20 decay time based on the impulse decay curve, -5 dB to -25 dB
T30 decay time based on the impulse decay curve, -5 dB to -35 dB
The Schroeder Method is also known as Backward Curve Integration0.001 s = 1 ms (millisecond) and 0.000001 s = 1 μs (microsecond)
Seismic Reflection the reflection of waves at boundaries between different rock formations
Seismic Refraction the refraction of waves passing through formations of 'earth' having different seismic velocities
Seismic Velocity the velocity of wave propagation in particular ground or rock formation
Seismograph A measuring instrument for detecting and measuring the intensity and direction and duration of movements of the ground (as in ground-borne vibration) - certified seismographs
See also other oscillation terms
Shock Pulse Definition IEC 801-24-27, excitation of a system characterized by rise and fall in a time interval short in comparison with the half-period of any mode of oscillation of the system
Duration of Shock Pulse Definition IEC 801-24-28, time required for the instantaneous value of an excitation to rise from some stated fraction of its maximum value and to decay to the same fractional value
There are 7 base units from which other units are derived and known as SI derived units.
SI Unit prefixes, used together with a SI unit to form decimal multiples or submultiples of the unitFactor | Name | Symbol | Multiplying Factor |
---|---|---|---|
1012 | tera | T | 1,000,000,000,000 |
109 | giga | G | 1,000,000,000 |
106 | mega | M | 1,000,000 |
103 | kilo | k | 1,000 |
10-3 | milli | m | 0.001 |
10-6 | micro | μ | 0.000.001 |
10-9 | nano | n | 0.000.000.001 |
10-12 | pico | p | 0.000.000.000.001 |
Example 10-6 g = 1 μg = 1 microgram or one millionth of a gram.
Sideband in frequency domain functions, pairs of frequencies with similar amplitude that appear equally spaced on either side of a centre frequency - produced by modulation.
SIL ▷ sound intensity level
SIL ▷ speech interference level.
Sine Wave or Pure Tone characterized by it's frequency (number of cycles per second) or it's wavelength (distance it travels within a period) and the amplitude .
Single Event Noise Exposure Level (SENEL) there are two variations of this term:-
1:- the dB(A) level which if it lasted for one second would produce the same A-weighted sound energy as the actual event.2:- similar except the start and end of the measurement is defined, usually as 10 dB below the Lmax
See also • T10
Both are similar on the SEL (sound exposure level) but we believe the second was developed to take account of single events like aircraft noise where the Lmax is important but the duration should also be taken factored in. An event with a higher Lmax can have a lower SEL than a longer event.
See also other hearing protector procedures
Single Number Rating (SNR) a rating system for duct silencers.
Slow Time Weighting is also known as slow response and slow time constant.
SNR ▷ see the Single Number Rating(s) above
By definition one sone = 40 phons and also equals 40 dB on the equal loudness contours.
A 10dB increase, from 40 to 50 phons sounds twice as loud, so 50 phons = 2 sones and the following table applies:-
Sone Definition IEC 801-29-04, unit of loudness, equal to the loudness of a pure tone presented frontally as a plane wave of frequency 1,000 Hz and a sound pressure level of 40 dB, re 20 μPa
● Note 1 : the loudness of a sound that is judged by the listener to be n times that of the 1-sone tone is n sones.
Sound Definition IEC 801-21-01, movement of particles in an elastic medium about an equilibrium position
Sound is also known as Acoustic Oscillation and Acoustic Vibration
See also • audible sound • complex sound • infrasound • speed of sound • ultrasound sound
Sound Energy
Sound Energy Density
Sound Energy Flux
Sound Energy Flux Density
Sound Energy Flux Density Level
Sound Exposure
Sound Exposure Level
Sound Exposure Meter
Sound Fields
Sound Field Quantities
Inverse Square Law
Particle Displacement
Particle Velocity
Sound Pressure
Sound Level
Sound Level Meter
Sound Level Meter Classes
See also the IEC Definition of Level
Sound Particle Acceleration.
Sound Particle Displacement.
Sound Particle Velocity.
Sound Power
Sound Power Absorption Coefficient
Sound Power Density
Sound Power Level
Sound Power Reflection Coefficient
Sound Pressure
Sound Pressure Level
Sound Pressure Reflection Coefficient
Sound Propagation Coefficient Definition IEC 801-23-33, with respect to a uniform system, natural logarithm of the complex ratio of particle velocities (or pressures) measured at two successive points separated by unit distance, when this system is assumed to be of infinite length, also known as the linear exponent of sound propagation
See also • elementary attenuation of propagation • elementary dephasing of sound propagation • elementary exponent of sound propagation • propagation loss definition
Sound Reduction Coefficient under noise reduction coefficient
Sound Reduction Index under sound insulation
Complex Sound Source composed of various sources, multiple frequencies and directivity patterns.
Point Sound Source Definition IEC 801-21-34, source that radiates sound as if from a single point.
Simple Sound Source Definition IEC 801-21-33, source that radiates sound equally in all directions in a free field and is also known as a monopole.
Strength of a Simple Sound Source Definition IEC 801-21-33, maximum instantaneous volume velocity produced by a simple source small compared with wavelength, emitting a wave with sinusoidal variation with time and is also known as the strength of a monopole.
See also • directivity • sound fields • sound waves
Sound Transmission passage of a sound wave through a medium or series of media.
Sound Transmission Class (STC)
Sound Transmission Loss (STL)
See also other types of averaging
Specific Acoustic Impedance Definition IEC 801-25-35, at a point in a sound field, quotient of sound pressure by particle velocity
See also acoustic impedance and related topics
Specific Energy the energy per unit mass, joule per kilogram = J/kg
See also • flow resistance
Other noise descriptors • ambient noise • background noise • broadband noise • gaussian noise • narrowband noise • periodic • pink noise • pseudo random noise • random noise • residual noise • white noise • wideband noise
Specific Volume (v) the number of cubic metres occupied by one kilogram of the substance : m3/kg.
See also acoustic impedance and related topics
Spectra is the plural of spectrum
Spectral Density Definition IEC 801-21-43, limit as the bandwidth approaches zero, of the mean square value of a field quantity divided by bandwidth. The kind of field quantity must be specified, such as sound pressure, particle velocity, particle acceleration. Also known as spectrum density
Spectral Density Limit as the bandwidth approaches zero, of the mean square value of a field quantity divided by bandwidth.
See also • energy spectral density.
Spectral Lines the number of constant bandwidth lines used in the measurement of spectra.
Spectrum the description of a sound wave's resolution into its components of frequency and amplitude.
See also • continuous spectrum • line spectrum
Spectrum Adaption Term (C and Ctr)
Spectrum Analyser an instrument to analyse a sound or vibration wave into it's frequency components. A spectrum analyser converts a signal from the time domain into the frequency domain,. The FFT, Octave and 1/3-octave analysers are the most common type today, but there are many other types.
See also other types of averaging
Spectrum Density Level Definition IEC 801-22-13, level of the limit, as the width of the band approaches zero, of the ratio of a specified quantity distributed within a frequency band to the width of the band.
● Note 1 : the kind of quantity must be specified, such as by (squared) sound pressure spectrum level.
● Note 2 : in view of the fact that filters have finite bandwidths, practically the sound pressure spectrum level Lps is obtained for the centre frequency of the band by the formula: Lps = 10 log10 (p2/B) ÷ (po2/Bo) dB,
where p and po are respectively the given field quantity and the reference quantity; B and Bo are respectively the effective bandwidth of the filter and the reference bandwidth of 1 Hz.
When Lp is the band sound pressure level observed through the filter, the above relation reduces to Lps = Lp - Log10 (B/Bo) dB
Speech - Articulation Index (AI)
Speech - Articulation Intelligibility
Speech - Clarity
Speech - Intelligibility
Speech Interference Level (SIL)
Speech Interference Level (SIL3)
Speech Power
Speech Privacy
Speech Transmission Index (STI and STIPA)
Sound travels faster in liquids and solids. For example the speed of sound in water is 1,480 m/s and for iron 5,120 m/s, these values are also temperature dependent, also giving rise to Sound Speed Gradients.
The frequency f, the wavelength λ and the wave velocity v are related by the formulae λ = v/f
Speed of Sound Definition IEC 801-23-18, magnitude of the phase velocity of a free progressive sound wave
The Speed of Sound should not to be confused with the Sound Particle Velocity.● Note : Spreading Loss exists, for example, for spherical waves emitted by a point source.
Spreading Loss is also known as divergence loss
Standing Wave Tube a method for measuring absorption coefficients by means of standing waves in a tube.
Stationary Signal a signal whose average statistical properties over a time interval of interest are constant. In general, the vibration signatures of rotating machines are stationary.
Stationary signals are either deterministic or random.
Statistical Analysis a calculation performed by a sound level meter on the noise levels measured during the measurement period to describe the statistical levels of the noise.
Statistical Noise Levels
Statistical Sound Power Absorption Coefficient
See also other oscillation terms
STI ▷ speech transmission index.
STIPA ▷ speech transmission index for public address systems
Stochastic the details of individual events may be unpredictable but the overall character of the sound is. For example rain falling, sound of insects, birds, etc.
Strength of a Monopole
Strength of a Simple Sound Source
Surface Area
Surface Normal
Surface Wave
Surface Wavefront
Symbol of a Quantity Definition IEC 112-01-03, character or combination of characters denoting a quantity.
● Note 1 : a simple quantity symbol is preferably one, or in some cases two, letters of the Latin or Greek alphabets and may include subscripts, superscripts, or other modifying signs. The letters are in italic (sloping) type, using preferably a font with serifs. The subscripts and superscripts are printed either in roman (upright) type, or, when they denote quantities, variables, or running numbers, in italic (sloping) type. Also known as quantity symbol.
See • ISO 80000-1 and IEC 60027-1 for more details and for the combination of symbols.
System of Units set of base units and derived units, together with their multiples and submultiples, defined in accordance with given rules, for a given system of quantities - see the SI units above
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