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 displacement, acceleration and velocity

Scalar Quantities may be added, subtracted or multiplied like ordinary numbers, vector quantities cannot.

**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

0.001 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

**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 therefore 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 |

Examples: 10^{-6} g = 1 μg = 1 microgram or one millionth of a gram.

**Watt (symbol: W)** is the SI derived unit of sound power, equivalent J/s. SI base unit kg·m^{2}·s^{-3}

**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 characterised 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 and SEL (sound exposure level)

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:-
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

**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 Absorption

Sound Absorption Coefficient

Sound Absorption Loss

Sound Diffraction

Sound Diffuse Field

Sound Diffusion

Sound Dose

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 Insulation

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

Sound Power Level

Sound Power Quantity

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 Reference Levels

See also reflected sound wave

**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

**Specific Noise Level** is the A-weighted, Leq level produced by a noise source during a specified period of time.

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 : m^{3}/kg.

See also acoustic impedance and related topics.

**Spectra** is the plural of spectrum

The **Spectral Density** of a wave, when multiplied by an appropriate factor, will give the power carried by the wave, per unit frequency, known as the
power spectral density of the wave and is commonly expressed in watts per
hertz (W/Hz).

**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.

**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)

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 (p^{2}/B) ÷ (po^{2}/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

Spelling

Spherical Wave

● Note : Spreading Loss exists, for example, for spherical waves emitted by a point source.

*Spreading Loss* is also known as divergence loss

Standard Atmospheric Pressure

Standardized Impact Sound Pressure Level (LnT)

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.

*Static Pressure* (symbol *p _{s}*)

**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 L10, L90 etc., statistical levels of the noise.

Statistical Sound Power Absorption Coefficient

See also other oscillation terms

**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 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.