1/1 octave bands

1/3 octave bands

See also • DC coupling.

velocity = a/ω and displacement = v/ω so at 159 Hz an acceleration of 10 m/s

If 1 N = 1 Kg·m/s

**Amax** is the maximum rms acceleration.

**Amin** is the minimum rms acceleration.

**Amp** is the maximum peak acceleration.

**aw** is the time-averaged, frequency-weighted, single-axis vibration acceleration.

See also • angular acceleration • particle acceleration, used in acoustic wave theory.

● Note 2 : the acceleration depends on the chosen reference frame.

● Note 3 : the coherent SI unit of acceleration is metre per second squared, m/s².

**Acceleration Level (La)** = 20 lg (a/ao) dB re 1 µm/s^{2}, where

a is the acceleration level in m/s^{2}, and

ao is the **acceleration reference level of 1 μm/s ^{2} ≡ 0 dB** (defined in ISO 1683) *

An increase or decrease in acceleration of 40 dB = a factor of 100

An increase or decrease in acceleration of 60 dB = a factor of 1000 etc.

● Note 2 : unless otherwise specified, the accelerations are understood to be expressed in rms values.

* ISO 1683 also states 'in connection with structure-borne sound, a vibratory acceleration reference value of 10 μm per second squared is also in use.

See other • reference levels and the IEC Definition of Level

To calculate the equivalent value for other periods use the formulae Aeq8 = a √T/8 where T = hours. Aeq4 and Aeq16 are also used in some vibration exposure applications.

See also • exposure action and limit values • hand arm vibration • vibration at work regulations • vibration dose value • whole body vibrationThe two most common accelerometer types are the traditional charge type and the IEPE : integrated electronic piezoelectric type with a built-in line-drive amplifier to enable the output signal to be transmitted over 'longer cable runs'.

See also • acoustic impedance and related topics

**Acoustic Impedance (Z)** is the ratio of the sound pressure (p) to the volume velocity (U) = p / U acoustic ohms, the SI unit is the pascal second per cubic metre.(Pa·s/m^{3})

**Acoustic Impedance** is a complex subject due to the wide range of sound and vibration situations found in the infrasound, hearing range and ultrasound fields not to mention structure borne noise and underwater acoustics. Further complications are introduced by phase differences when dealing with both vectorial and scalar quantities. See the list of related links below, developed to deal with **specific situations**.

See also • acoustic admittance • acoustic ohm • acoustic reactance • acoustic resistance • characteristic acoustic impedance • characteristic impedance of a medium • complex acoustic impedance • conjugate impedances • driving point impedance • impedance • specific acoustic admittance • specific acoustic impedance • specific acoustic reactance • specific acoustic resistance • specific wall admittance • specific wall impedance • transfer impedance • transmission impedance and radiation

See also • acoustic impedance and related topics

See also • audible sound • oscillation

Acoustic Reference Levels

Acoustic Reference Wind Speed

See also acoustic impedance and related topics

See also • audible sound • oscillation

See also phase cancellation

Active Sound Fields

Active Sound Intensity

See also • acoustic admittance

Indicators • LAeq,16h • Lday • Levening.

Air Density

See also • anti-aliasing filter • nyquist frequency

Other noise descriptors • background noise • broadband noise • gaussian noise • narrowband noise • periodic • pink noise • pseudo random noise • random noise • residual noise • specific noise • white noise • wideband noise

1 ampere is equivalent to 1 Coulomb per second.

See also • reverberation

Units | Values | |||||||
---|---|---|---|---|---|---|---|---|

Degrees | 0° | 30° | 45° | 60° | 90° | 180° | 270° | 360° |

Radian | 0 | π/6 | π4 | π/3 | π/2 | π | 3 π/2 | 2π |

Grads | 0^{g } | 100^{g}/3 | 50^{g} | 200^{g}/3 | 100^{g} | 200^{g} | 300^{g} | 400^{g} |

**Angular Momentum (L)** is the quantity of rotation of a body, which is the product of the moment of Inertia and it's angular velocity, units newton metre seconds (N·m·s)

See also • nyquist frequency.

Antinode

See also • resonance

Apparent Sound Insulation Index (R')

Apparent Sound Power Level

Weighted Apparent Sound Reduction Index (R'w)

**Surface Area**, refers to the total area of the exposed surface of a 3-dimensional solid.
The derived SI unit is the square metre, symbol m^{2}, 1 m^{2} = 1 m by 1 m or 2 m by 0.5 m, etc., 25 mm by 25 mm = 0.025 m by 0.025 m = 0.000625 m^{2}

See also averaging sound levels • decibel calculations

Articulation Class (AC)

Articulation Index (AI)

ASA • Acoustical Society of America

Atmospheric Sound Absorption

a) acoustic oscillation of such character as to be capable of exciting a sensation of hearing.

b) sensation of hearing excited by an acoustic oscillation or vibration.

*Audible Threshold* • under threshold of hearing.

See also • auditory masking • masked threshold • threshold shift

See also • critical bands • threshold of hearing.

*Average Sound Level Meters* - see integrating sound level meters

*Average Sound Pressure* - under effective sound pressure

*Average Sound Pressure Level* - in a room, under sound insulation

Average Speech Power

See also • arithmetic mean • effective level • ensemble averaging • exponential averaging • linear averaging • mean square • power spectrum averaging • rms averaging • spatial averaging • spectrum averaging • time-average sound level • time-average sound pressure level • time domain averaging • time weightings

Axial Modes

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