Sabin

Sabin Absorption

Sabine

Sabine Sound Absorption Coefficient

Sabine Equation

**Sampling Frequency** the rate at which a continuous waveform is digitised, given in Hz.

**Sampling Interval** how long the data is measured at each sample point.

**Sampling Theorem** says that ideally a signal should be sampled at a rate twice its highest frequency component.

**Scalar Quantity** a quantity fully described by a magnitude or numerical value, for example density, mass and speed.
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.

**Schroeder** method for calculating the reverberation time from the impulse noise decay curve. The backward curve integration algorithm developed by Manfred Schroeder at Bell Labs in the nineteen-sixties.

**Second (s)** the second, symbol s, is the name of the SI base unit of time.

0.001 s = 1 ms millisecond : 0.000001 s = 1 μs microsecond

**Seismic** relating to earthquakes or other vibration in the earth

**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

**Seismogram** a record produced by a seismograph

**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

**Serial Frequency Analysis** the measurement of octave or third octave bands of noise where a single filter is stepped across the different bands one at a time. Superseded by real time analysis, these days.

**SI Units** the world's most widely system of units devised around the convenience of the number 10.

There are 7 base units from which other units are derived and known as **SI derived units**.

Factor | Name | Symbol | Multiplying Factor |
---|---|---|---|

10^{12} | tera | T | 1,000,000,000,000 |

10^{9} | giga | G | 1,000,000,000 |

10^{6} | mega | M | 1,000,000 |

10^{3} | 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 Sound Exposure level (SEL) 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**.

**Single Number Rating (SNR)** a single number rating system for hearing protectors - BS EN ISO 4869

See also • noise reduction rating used in the USA.

**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 Single Number Rating 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:-
40 phon = 1 sone

50 phon = 2 sones

60 phon = 4 sones

70 phon = 8 sones

80 phon = 16 sones

90 phon = 32 sones ... and so on

50 phon = 2 sones

60 phon = 4 sones

70 phon = 8 sones

80 phon = 16 sones

90 phon = 32 sones ... and so on

● 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.

See also • audible sound • complex sound • infrasound sound • speed of sound • ultrasound sound

Sound Absorption

Sound Absorption Coefficient

Sound Absorption Loss

Sound Analyser *under* Spectrum Analyser.

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 Intensity

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 IEC 801-211-8

Sound Power Level

Sound Power Reflection Coefficient

Sound Power through a Surface Element is also known as Sound Energy Flux

Sound Pressure

Sound Pressure Level

Sound Pressure Reflection Coefficient

See also • elementary attenuation of propagation • elementary dephasing of sound propagation • elementary exponent of sound propagation

**Sound Rating Level (LArT)**, the A-weighted, Leq, sound pressure level of an industrial noise during a specified time period, adjusted for tonal character and impulsiveness

**Sound Reduction Coefficient** under Noise Reduction Coefficient.

**Sound Reduction Index** under Sound Insulation.

Sound Reference Levels

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)

Sound Waves

Sound Wave Velocity

**Spatial Averaging** taking measurements at various positions and averaging the results. Mandatory in sound insulation measurements and recommended anywhere multiple reflections are present.

See also other types of averaging

**Spatial Frequency** is a measure of how often sinusoidal components of the structure repeat per unit of distance. The SI unit of spatial frequency is cycles per meter.

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 • 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 : m^{3}/kg.

See also acoustic impedance and related topics

**Spectra** is the plural of spectrum

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.

**Spectrum Averaging** a short term spectrum analysis may include information due to external sources, for example background noise. Repeating the measurements over a longer period and averaging the spectra will cause any random signals to be 'discarded' and your confidence in the measurement will improve.

See also other types of averaging

*Spectrum Density* is also known as *spectral density*

● 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 (p

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

Spectrum Level under Spectrum Density Level

Speech - Articulation Index (AI)

Speech - Articulation Intelligibility

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

The Speed of Sound should not to be confused with the Sound Particle Velocity.

Spelling

Spherical Wave

● Note : Spreading Loss exists, for example, for spherical waves emitted by a point source, also known as the

**Square** when you multiply a whole number times itself, the resulting product is called a square number, or a perfect square or simply a square.

**square metre (m ^{2})** Area

**square root (√)** the square root of a number is a smaller number that, when multiplied by itself equals the original number.

Standard Atmospheric Pressure

Standardized Impact Sound Pressure Level (LnT)

Standardized Impact Sound Pressure Level (L'nT)

Standardized Level Difference (DnT)

Standardized Impact Sound Pressure Level (L'nT)

Standardized Level Difference (DnT)

Standard Reference Levels

Standing Wave

*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

**Symbols** the names, symbols and definitions for quantities and units of acoustics are given in BS EN ISO 80000-8 - BSI copyright precludes us publishing any standard. However we can state 'well-known' general facts

● 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

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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