AbsorptionThe changing of energy to heat which reduces the amount of energy which can be reflected.
AdhesionThe sticking of the gasket material to either or both flanges of a mechanical assembly.
Airborne soundSound that arrives at the point of interest, by propagation through air.
Alloy-steelA type of steel that contains additional elements to improve the properties of a fastener.
AluminumA silvery, white metal that is soft, light, and is electrically and thermally conductive.
AmbienceThe acoustic characteristics of a space with regard to reverberation. A room with a lot of reverb is said to be "live"; one without much reverb is said to be "dead".
Ambient noiseThe composite of airborne sound from many sources near and far associated with a given environment. No particular sound is singled out for interest.
AmplitudeThe instantaneous magnitude of an oscillating quantity such as sound pressure. The peak amplitude is the maximum value.
Anechoic chamberA room designed to suppress internal sound reflections. Used for acoustical measurements.
AntifreezeAntifreeze/Coolant is a combination of chemicals designed to be mixed with water for use in engine cooling systems. Antifreeze most commonly use glycols (either ethylene or propylene) to reduce the freezing point of water.
AntistickA coating or surface treatment that prevents the gasket material from adhering to the flanges.
Audible frequency rangeThe range of sound frequencies normally heard by the human ear. The audible range spans from 20Hz to 20,000Hz.
B100 BiodieselB100 is 100% biodiesel. (See Biodiesel.)
Background noiseNoise from all sources unrelated to a particular sound that is the object of interest. Background noise may include airborne, structureborne, and instrument noise.
BaffleA free hanging sound absorbing unit used for reduction of reverberation and noise levels.
BassThe lower range of audible frequencies.
BeatsPeriodic fluctuations that are heard when sounds of slightly different frequencies are superimposed.
BinderThe elastomer or rubber used in gasket material.
BiodieselBiodiesel is an ester made from fats or oils (renewable resources such vegetable oils, animal fats, or other types of biomass). B100 is 100% biodiesel.
BiofuelBiofuels are liquid fuels made from esters, alcohols, ethers, and other biomass chemicals
BlowoutOccurs when internal pressure tends to push the gasket material out from between flanges. Blowout usually occurs in areas of low flange pressure and high internal pressure.
Bolt fractureA type of fastener failure that occurs when a fastener is over-tightened and causes the bolt to break.
Bolt LengthA gasket selection and flange design factor that includes the "effective bolt length" (defined as the distance from theunderside of the bolt head to the closest engaged thread), the washer, and the thickness of the compressed gasket.
Bolt LoadingThe load generated by a bolt when it is tightened.
Bolt-Hole DistortionFlange is permanently distorted directly beneath the bolt. Caused by initial bolt torque.
Brinell scaleA method for testing a material's hardness that forces a hard steel sphere under a specified load into the surface of a material and measuring the diameter of the indentation left after the test.
Broad band noiseSpectrum consisting of a large number of frequency components, none of which is individually dominant.
Broken CornerA corner of a mechanical assembly that is "broken off" instead of being machined into a perfect radius. Usually done to reduce manufacturing costs.
BronzeAn alloy of copper and tin. Bronze is highly corrosion resistant.
Carbon steelA type of steel made up of iron and carbon and no other material. Most fasteners are made from carbon steel.
Chemical ResistanceA gasket material's degradation resistance to the fluid or fluids being sealed.
Clamping forceThe compressive force that a fastener exerts on a joint.
CockingWhen the flanges of a mechanical assembly are not parallel to each other.
Cold workingThe shaping of metal at temperatures much lower than the metal's molten state. Cold working increases the strength in certain steels.
CompressibilityThe amount (%) of material thickness reduction that occurs when the proper external load is applied to a material.
Compression SetThe residual deformation of a material after removal of the compressive stress.
ConformabilityThe ability of a gasket material to conform to flange surface roughness and out-of-flatness.
Controlled SwellA gasket material that exhibits a controlled increase in thickness (swell) in the presence of oil.
CopperA reddish-brown metal that is very ductile, thermally and electrically conductive, and corrosion resistant. Copper fasteners are often used for electrical components.
Corrosion resistanceThe ability of a material to resist chemical destruction from an environment. Corrosion resistance is one of the most important physical property for fasteners.
Creep RelaxationA transient stress strain condition in which the strain increases concurrently with the decay of stress.
Crush ResistanceA measurement of a gasket material's ability to resist initial bolt load and/or extreme stress generated by the expansion of a bolted assembly upon heating.
DampTo cause a loss or dissipation of vibrational energy in solid media and structures.
dB(A)The frequency response curve which resembles the normal frequency hearing curve for most people. A sound-level meter reading with an A-weighting network simulating the human-ear response at a loudness level of 40 phons.
dB(B)A sound-level meter reading with a B-weighting network simulating the human-ear response at a loudness level of 70 phons.
dB(C)A sound-level meter reading with no weighting network in the circuit, i.e., flat. The reference level is 20 uPa.
DecadeTen times any quantity or frequency range. The range of the human ear is about 3 decades.
Decay rateFor airborne sound, the rate of decrease of vibratory acceleration, velocity, or displacement level after the excitation has stopped.
Decibel (dB)The standard measure of loudness. dB is a ratio of two quantities on a logarithmic scale.
DensityThe relative compactness of a material. Density is the mass of a material per unit volume.
DiffractionA change in the direction of propagation of sound energy in the neighborhood of a boundary discontinuity, such as the edge of a reflective or absorptive surface.
Diffuse fieldAn environment in which the sound pressure level is the same at all locations and the flow of sound energy is equally probable in all directions.
Dimensional StabilityHow well a cut gasket retains its original dimensions when exposed to temperature and humidity extremes.
DuctilityThe ability of the material to deform before it fractures.
Elastic ModulusSee Young's Elastic Modulus.
Electrical conductivityThe ability of a material to conduct an electrical current.
EuphonicAs a descriptive audio term, usually refers to a coloration or inaccuracy that none-the-less may be sonically pleasing.
FatigueA type of fastener failure that occurs when a fastener is subjected to repetitive loading or stressing. Fatigue can cause catastrophic failure
Feedback, acousticUnwanted interaction between the output and input of an acoustical system, e.g., between the loudspeaker and the microphone of a system.
FerrousA metal that contains iron. Carbon steels are common ferrous metals
FilletA curved or rounded portion of a mechanical assembly.
FlangeA rib or rim for strength, guiding, or attachment of one object to another. In a gasketed joint, a flange performs all three of these functions.
Flanking transmissionTransmission of sound from the source to a receiving location by a path other than that under consideration. These noise flanking paths can defeat noise reduction techniques.
Free fieldAn environment in which a sound wave may propagate in all directions without obstructions or reflections. Anechoic rooms can produce such an environment under controlled conditions.
FrequencyAll sounds can be described by their frequency or their mix of frequencies, and can be measured on a scale in units of Hertz (Hz), expressing the number of cycles per second.
FundamentalThe lowest frequency of a note in a complex wave form or chord.
Fusion zoneAll reflections arriving at the observer's ear within 20 to 40 msec of the direct sound are integrated, or fused together, with a resulting apparent increase in level and a pleasant change of character. This is the Haas effect.
GasketA material, combination of materials, or a device used to create and maintain an impervious barrier against the transfer of fluids across the separable surfaces of a mechanical assembly (joint) that do not move relative to one another.
Gasket ExtrusionRefers to the tendency of a gasket to flow from between flanges, particularly around bolt holes where stresses are concentrated.
GradeA category that fasteners are grouped in according to their strength.
Grain Listening termA sonic analog of the grain seen in photos. A sort of "grittiness" added to the sound.
H2SO4Sulphuric acid is a strong mineral acid. It is soluble in water at all concentrations
Haas effectSee fusion zone. Also called the precedence effect. Delayed sounds are integrated by the auditory apparatus if the fall on the ear within 20 to 40 msec of the direct sound. The level of the delayed components contributes to the apparent level of the sound, and it is accompanied by a pleasant change in character.
Hard roomA room in which the surfaces have very low values of sound absorption and are therefore highly reflective.
HardnessThe resistance to indentation. Usually measured with a durometer.
HarmonicsAlso called overtones, these are vibrations at frequencies that are multiples of the fundamentals. Harmonics extend without limit beyond the audible range. They are characterized as even-order and odd-order harmonics. A second-order harmonic is two times the frequency of the fundamental; a third order is three times the fundamental; a fourth order is four times the fundamental; and so forth. Each even-order harmonic second, fourth, sixth, etc.-is one octave or multiples of one octave higher than the fundamental; these even-order overtones are therefore musically related to the fundamental. Odd-order harmonics, on the other hand third, fifth, seventh, and up-create a series of notes that are not related to any octave overtones and therefore may have an unpleasant sound. Audio systems that emphasize odd-order harmonics tend to have a harsh, hard quality.
Heat treatmentThe heating and cooling processes used to change the structure of a material and alter its mechanical properties.
Hex-head boltA type of bolt that has a head with six sides.
ImpedanceThe opposition to the flow of electric or acoustic energy measured in ohms.
ImpulseA very short, transient, electric or acoustic signal.
Impulse responseSound pressure versus time measurement showing how a device or room responds to an impulse.
In phaseTwo periodic waves reaching peaks and going through zero at the same instant are said to be "in phase."
Initial Flange PressureThe stress on a gasket attained when a joint is initially tightened.
IntensityAcoustic intensity is sound energy flux per unit area. The average rate of sound energy transmitted through a unit area normal to the direction of sound transmission.
InterferenceThe combining of two or more signals results in an interaction called interference. This may be constructive or destructive. Another use of the term is to refer to undesired signals.
IsolateA dampening mechanism made a part of the assembly or system, which reduces structure borne vibrations from passing through the structure.
JointTerm used for a mechanical assembly or gasketed assembly.
Load/CompressionThickness reduction that occurs with a given gasket material at various known applied external loads, thereby establishing a load/compression curve.
LogarithmAn exponent of 10 in the common logarithms to the base 10. For example, 10 to the exponent 2=100; the log of 100=2.
LoudnessA subjective term for the sensation of the magnitude of sound. The subjective response to a sound level.
Low-carbon steelA type of carbon steel that contains less than 0.3% carbon.
LS DieselLow Sulphur Diesel Fuel(< 50ppm sulphur content)
Mass lawAn approximation that describes the Sound Transmission Loss (TL) of a limp, flexible barrier in terms of mass density and frequency. For each doubling of the weight or frequency of a partition, mass law predicts a 6 dB increase in TL.
Medium-carbon steelA type of carbon steel that contains between 0.3% and 0.5% carbon.
MEGMonoethylene Glycol. (See Antifreeze.)
Metric sabin [L2]The unit of measure of sound absorption in the metre-kilogram-second system of units.
NaClSodium Chloride (vulgar table salt)
NaOHSodium hydroxide (NaOH), also known as lye or caustic soda, is a caustic metallic base. It is widely used in industry, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, and detergents
Near fieldLocations close to the sound source between the source and the far field. The near field is typically characterized by large sound pressure level variations with small changes in measurement position from the source.
NoiseInterference of an electrical or acoustical nature. Unwanted, bothersome, or distracting sound.
Non-ferrousA metal that does not contain iron. Aluminum, copper, and zinc are nonferrous metals.
OctaveAn octave is a doubling or halving of frequency. 20Hz-40Hz is often considered the bottom octave. For example, each octave you add on the bottom requires that a speaker to move four times as much air!
Octave bandsFrequency ranges in which the upper limit of each band is twice the lower limit. Octave bands are identified by their geometric mean frequency, or center frequency.
OvertoneA component of a complex tone having a frequency higher than the fundamental.
PEGMonopropylene Glycol. (See Antifreeze.)
PhasePhase is the measure of progression of a periodic wave. Phase identifies the position at any instant which a periodic wave occupies in its cycle. It can also be discribed as the time relationship between two signals.
Phase shiftThe time or angular difference between two signals.
PhonThe unit of loudness level of a tone.
Pink noiseNoise with a continuous frequency spectrum and with equal power per constant percentage bandwidth. For example, equal power is any one-third octave band.
PitchA subjective term for the perceived frequency of a tone.
PreloadThe load that sufficiently stretches the bolt/screw to give a tight joint and overcome any forces tending to pull the joint apart. (See Proof Load.)
Pressure zoneAs sound waves strike a solid surface, the particle velocity is zero at the surface and the pressure is high, thus creating a high-pressure layer near the surface.
ProfilometerDevice that measures flange surface roughness.
Proof LoadThe amount of stress that the fastener can withstand without experiencing deformation. Proof load is often used interchangeably with yield strength. (See Yield Strength.)
Pure toneA tone with no harmonics. All energy is concentrated at a single frequency.
RarefactionThe portion of a sound wave in which molecules are spread apart, forming a region with lower-than-normal atmospheric pressure.
ReflectionFor large surfaces compared to the wavelength of impinging sound, sound is reflected much as light is reflected, with the angle of incidence equaling the angle of reflection.
RefractionThe bending of sound waves traveling through layered media with different sound velocities.
ResonanceA natural periodicity, or the reinforcement associated with this periodicity.
Resonant frequencyAny system has a resonance at some particular frequency. At that frequency, even a slight amount of energy can cause the system to vibrate. This is its natural or resonant frequency.
ReverberationThe persistence of sound in an enclosed or partially enclosed space after the source of sound has stopped.
Reverberation timeThe tailing off of a sound in an enclosure because of multiple reflections from the boundaries.
Rockwell scaleA method for testing a material's hardness that uses an indenter to test the material's resistance to deformation as a load is applied.
Root Mean Square (RMS)Term used to express surface texture. It is the average deviation from the mean surface.
RwThe weighted sound reduction index (excludes the effects of flanking transmission)
R'wThe apparent weighted sound reduction index (includes the effects of flanking transmission)
Seal PointThe minimum stress needed on a gasket material to achieve an effective seal.
Sealing StressThe amount of flange pressure present in a flanged joint assembly to compress and seat a gasket material in order to create an effective seal.
Shear strengthThe ability of a fastener material to resist internal sliding.
Sine waveA periodic wave related to simple harmonic motion.
Socket screwA type of capscrew with a round head and a hexagonal indentation for tightening purposes.
SoneThe unit of measurement for subjective loudness.
SoundSound is vibrational disturbance, exciting hearing mechanisms, transmitted in a predictable manner determined by the medium through which it propagates. To be audible the disturbance must fall within the frequency range 20Hz to 20,000Hz.
Sound absorption(1) The process of dissipating sound energy.
(2) The property possessed by materials, objects and structures such as rooms of absorbing sound energy.
(3) A: [L2]; metric sabin---in a specified frequency band, the measure of the magnitude of the absorptive property of a material, an object, or a structure such as a room.