Acoustic Glossary
Sound and Vibration Terms and Parameters
M
m2 : square metre : area.
m3 : cubic metre : volume.
m3/s : cubic metre per second : volumetric flow.
m/s : metre per second : speed velocity
m/s2 : metre per second squared : acceleration.
m/s3 : metre per second cubed : jerk.
MAF : Minimum Audible Field.
Magnetic Field : a region around a magnetic material or a moving electric charge within which the force of magnetism acts. The SI Unit is the Tesla.
Magnetic Induction :
1:- magnetic flux of flux density
2:- the process by which an object or material is magnetized by an external magnetic field.
Masking Noise : a noise that is intense enough to render inaudible or unintelligible another sound that is also present - also known as auditory masking.
Mass : m : the quantity of matter which a body contains as measured by it's acceleration under a given force or on the force exerted on it by gravity. In the SI system of units mass is measured in kilograms and the symbol is kg
1 kg = 1000 g = 10-3 tonne
Mass Density : kilogram per cubic metre - kg/m3 - see also density of air
Mass Flow Rate : kilogram per second - kg/s
Mass Law : a doubling in mass or frequency results in a 6 dB increase in insulation for a single leaf partition over a defined frequency range.
Maximum Length Sequence : MLS - is basically a pseudo-random sequence of pulses. MLS measurements are quite standard in many different application fields, one of them acoustics. For more details click here.
Maximum Peak : treat with caution, by definition there can only be one peak value and this requires a special detector circuit many meters do not have - see peak It is sometimes used with LCpk or LLpk.
Maximum Perceived Noise Level : PNLmax : Perceived Noise Level
Maximum Sound Level : Lmax : the maximum noise level during a measurement period or a noise event - should also include other descriptors i.e. A, C, L or Z weightings and F, S or I time constants. Sometimes written as Max dB(A)
mb : millibar : a common metric unit of atmospheric pressure 1 mb = 0.001 bar, 100 pascals.
mega : M : SI prefix = 106 see other SI Units
metre : m : is the basic unit of length in the metric system and in the International System of Units (SI).
1 metre = 39.370 inches = 3.2808 ft.
1000 m = 1 km kilometre : 0.01 m = 1 cm centimetre : 0.001 m = 1 mm millimetre.
metre per second : m/s : unit of speed, velocity
metre per second cubed : m/s3 : jerk.
metre per second squared : m/s2 : acceleration.
micro : μ : SI prefix = 10-6 see other SI prefixes
microbar : µbar : 0.001 millibar = 0.1 pascal = 1 dyne per square centimetre : a CGS unit of pressure.
micrometre : µm : 0.000001 m
micron : μ : see micrometer
microsecond : µs : 0.000001 second
Mid-band Frequency : the centre frequency of a band pass filter, defined as the geometric mean of the upper and lower frequencies.
mil : a unit of distance = 0.001 inch - thousandths of an inch. Usually measured in mils peak to peak, which represents total displacement. 1 mil = 25.4 microns.
milli : m : SI prefix = 10-3 see other SI Units
millibar : mb : a common metric unit of atmospheric pressure, One hundredth of a bar.
1 mb = 0.001 bar = 100 Pa, pascals. A pascal is one newton per square metre.
millimetre : mm : 0.01 metre
milliwatt : mW : 0.001 watt
millisecond : ms : 0.01 second
Minimum Audible Field : MAF : the zero phon curve on the equal loudness contours.
Minimum Sound Level : Lmin : the minimum noise level during a designated time interval or a noise event - should also include other descriptors i.e. A, C, L or Z weightings and F, S or I time constants. Sometimes shown as Min dB(A)
MLS : Maximum Length Sequence.
mm : millimetre : 0.01 metre
Modal Analysis : is a process of determining the natural frequencies, damping factors, and mode shapes for a structure. This is usually done either experimentally through frequency response testing or mathematically using finite element analysis.
Mode : a room resonance. Axial modes in rectangular rooms are associated with pairs of parallel walls. Tangential modes involve four room surfaces and oblique modes all six surfaces. Their effect is greatest at low frequencies and for small rooms.
Modulation : a process by which a spectral component is modified by another component and sidebands result.
Modulation Transfer Function MTF : the extent to which the fluctuations in the original signal are preserved in the signal reaching the listener. In the field of speech intelligibility, the difference between the original spectrum and the spectrum of the reverberated signal.
Moment : a turning effect produced by a force acting acting at a distance on an object.
Moment of Force : see Torque
Moment of Inertia : a quantity expressing a body's tendency to to resist angular acceleration.
Moment of Momentum : kilogram metre squared per second - kg·m2/s
Momentum : p : = m·v = the motion of a moving body, measured as a product of it's mass and velocity - units: N·s = kg·m/s
Monaural Sound Recording : a sound recording in which only one channel is used. If two channels (stereo or binaural sound) are available but only one channel is chosen, then the left channel is usually chosen by default.
ms : millisecond : 0.01 second
MSHA : Mine Safety and Health Administration : USA.
Multi-spectrum : A one or two dimensional array of spectra. A multi-spectrum consists of two or more spectra that were recorded during the same measurement - more information
Other Glossary Terms
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