Some standard content:
GB/T 39471996
This standard is a revision of the national standard GB3917-83 "Acoustic Terminology". Since its release and implementation, GB3947-83 has played a role in unifying concepts in the use of scientific research, education, and production equipment, so that relevant personnel have a common language for the basic terms of acoustics, and has become the main theoretical basis for the formulation of acoustic standards. At the same time, after years of use, some entries have been proposed for revision, and the public generally hopes to expand the content and add entries, so it is decided to revise GB3947-83 "Acoustic Terminology" The content includes standard nouns and standard definitions. GB3947-83 contains 1445 standard terms, 535 of which are defined. The technical standard increases the number of standard terms to 2899, and defines 914 of them. 49 of the original terms are supplemented and modified, and 145 are modified in wording. The appendix A and appendix B of this standard are both standard appendices. This standard replaces GB3917-83 from the date of entry into force. This standard is proposed and managed by the National Acoustic Standard Promotion Technical Committee. The drafting unit of this standard is the Institute of Acoustics, Chinese Academy of Sciences. The main drafters of this standard are Ma Daxian, Dai Genhua, Zhang Ruwei, Xu Weiyi, Yang Jingang, and Zhu Houqing. 1 Scope
National Standard of the People's Republic of China
Acoustical terminology
Acoustical terminology
This standard provides the commonly used and basic terms and terms in acoustics and related acoustics. GB/T 3947—1996
Replaces GB3917—83
This standard gives a total of 914 acoustic terms, divided into 13 chapters (Chapter 211). When a term has two or more definitions of different natures, it is described in parallel in a, b, and c lines. Appendix A is the Chinese and English acoustic terms, arranged in the order of Chinese pinyin, and this appendix also serves as the Chinese index of acoustic terms. Appendix B is the English and Chinese acoustic terms, arranged in alphabetical order, and also serves as the English index of acoustic terms. ||tt| |When there are two or more synonyms for the nouns (in Chinese or English) listed in this standard of acoustic terminology, for nouns that are not distinguished, it means that these nouns have the same status and can be used. For nouns in parentheses (, generally means that they have been used in the past and can still be used now, but this standard does not recommend it. The word list in square brackets can be omitted. The words in round () in the definition are generally annotations. The words in brackets in the nouns are mainly based on the regulations of the listed disciplines. Italics indicate pinyin. 2 General terms
2. Sound wave [sound wave] [wave] [sound wave ...
h. Hearing caused by sound waves
1 The range of audible sound is roughly 20[z to 201z. 2 Audible sound is generally referred to as sound or voice
3 According to the definition, sound is a general term, and voice is a tonal sound. According to the definition (h), it is also called sound or ringing. The three should be distinguished. The State Administration of Technical Supervision approved it on September 13, 1996 and implemented it on March 1, 1997
GB/T3947-1996
2.9 Ultrasound, ultrasonic sound The sound with a frequency higher than the upper limit of the audible sound frequency.
Note: The lower limit of ultrasonic frequency is 20 kIIz. 2.10 Infrasound, infra audible sound, infrasonic Sound whose frequency is lower than the lower limit of audible sound frequency. Note: The upper limit is approximately 20Hz. 2.11 Noise noise is a chaotic, intermittent or statistically random sound oscillation; a. Unwanted sound is sometimes called unjitched sound. b. Unwanted sound can be referred to as any unwanted interference in a certain frequency band, such as radio waves. Note: It should be called "unsound noise" or "radio noise" when it is mixed. 2.12 Random noise domnois
Sound oscillation whose instantaneous value cannot be determined in advance. The distribution of the instantaneous value of random noise over time only obeys a certain statistical distribution law. Note: Random noise is not necessarily white noise. 2.13 White noise is also called white noise
Noise whose spectrum is continuous and uniform when measured with a fixed bandwidth. The power attenuation of white noise does not change with frequency. Note: domnoise is not necessarily random noise. 2.14 Pink noise Pink noise is noise whose spectrum is continuous and uniform when measured with a bandwidth proportional to the frequency. The power spectrum density of pink noise is inversely proportional to the frequency.
2. 15 Amphibiant noise Environmental noise is the total noise in a certain environment. It is usually generated by multiple sound sources in different locations. Background noise background noise background noise
"Ten interferences" that are irrelevant to the presence or absence of signals in the system of inspection, measurement and recording. 2.17 Speed of sound speed sound velocity nfaannrtsoundvelocity The speed at which sound waves propagate in a medium, measured in meters per second, /s. 2.18 Velocity gradient xcund velocily gradient The rate of change of sound velocity along the depth of water or height in the atmosphere. A positive rate of change (the speed of sound increases with increasing depth or height) is called a positive gradient; a negative rate of change (the speed of sound decreases with increasing depth or height) is called a negative gradient. Sound velocity profile soundvelocity profile 2.19
The function of how sound velocity changes with depth or height. Static pressure (,{p) static prexsure
The pressure in a medium when there is no sound wave, measured in Pascals, Pa: 2-21 Sound (p) sound prcssurc
The sum of the pressure and the residual pressure in the medium when there is a sound wave. The unit is Pascal, Pa. Notes
1 Generally speaking, sound pressure is the abbreviation of effective sound pressure. Effective sound pressure is the root mean square value of the sound pressure during a period of time. This period should be an integer of the period or a degree that does not affect the calculation result. 2 The time value, average value, integer, maximum value or peak-to-peak value of sound pressure should be respectively called time, average sound pressure, peak sound pressure, maximum sound pressure or peak-to-peak displacement.
2.22 Particle displacement (,()sound [parlicle dlisplacement The displacement of a particle in a medium that is very small in size but larger than the wavelength and is on the scale of a molecule due to the passage of sound waves. The unit is meter, m.
Lan: If not specified, it generally refers to the effective value (i.e. the root mean square value). When using other terms, it should be said that sound pressure (2.21) Note 2. GB/T3947—1996
2.23 Particle velocity (u.) soundparliclevelucity The displacement of a particle in a medium that is very small in size but larger than the wavelength and is on the scale of a molecule due to the passage of sound waves. The vibration velocity relative to its equilibrium position, in meters per second, m/. Note: If not specified, it generally refers to the effective value (i.e., the root mean square value). If other values are used, they should be specified, such as sound pressure (2.21) Note 2. Particle acceleration (a) [suundparticleacceleratinn2.24
The time rate of change of particle velocity, in meters per second, m/ Note: If not specified, it generally refers to the effective value (i.e., the root mean square value). If other values are used, they should be specified, such as sound pressure (2.21) Note 2, 2.25 Volume velocity (, (.) volume velocity The alternating current between each single particle generated by sound waves on a specified surface, in cubic meters per second,m/s,
1 The volume velocity is expressed as
where. It is the component of the surface area between the points. In the table S1, 2 is not added, generally refers to the effective value (that is, the square root value), and other explanations should be given when used, such as sound pressure (2.21) Note 2.3 The rest volume velocity is called \body milk flow (olumetiuwtatc)\. 2.26jf intensity [J(1,J) sound intensity (sound energy flux density, sound power density) At a point in the sound field, the product of the sound energy passing through the unit time perpendicular to the direction of the particle velocity is called instantaneous sound intensity. It is a lossy unit and is:
(c) p() -u(2)
Instantaneous sound intensity, W/m\:
Instantaneous pressure, Pa
Instantaneous particle velocity, m,/.
In a steady-state sound field, the sound intensity 1 is the average value of the instantaneous sound intensity within a certain time T, in watts per square meter, W/m. The expression for the intensity is:
ndt
p)·utde
Where: multiples of a period, or a time that is long enough not to affect the calculation result, Note:
1 The sound intensity in the direction to the left is equal to ·n;
2 In the case of a plane wave or a spherical front wave, the sound intensity in the propagation direction is f, = /nc
In the play: p——effective sound pressure, Pai
medium density, kg/nl;
sound speed, m/s.
2.27 Sound intensity measurement The ratio of the difference in the sound pressure of two points with a height of r (·r≤) in the middle of the sound field measured by two microphones with similar characteristics to;△| is used to represent the sound pressure gradient at the midpoint of the line connecting the two points, so as to obtain the particle velocity. The sound pressure at the midpoint is represented by the average value of the sound pressures at the two points. The product of the particle velocity and the sound pressure at the midpoint is averaged over a sufficiently long time, that is, the sound intensity in the direction A of the point is measured:
2.28 Sound source strength (Q) strength of a sound source is simply the maximum volume velocity of a sound source when it emits a chord-like wave, in cubic meters per second, m/s. Note 1 Simple sound source is a sound source whose size is smaller than the wavelength. 2.29
Sound energy density (w,e,D) The sound energy in a small volume at a point with a size much smaller than the wavelength but much larger than the wavelength is divided by the volume. The unit is [|per cubic meter, J/m.
GB/T 3947—1996
1 It is better not to specify, generally refers to the effective value (i.e. the square root value), and other values should be specified when used, such as sound pressure (2.21) Note 22 When talking about average sound density, it is necessary to specify whether it is spatial average (at a certain moment) or time average (at a certain point). 3 The average medium energy density at the benzene point is equal to
In the formula:
Effective sound pressure,
P-medium density. kg/m.
m/s
2.30 Sound power (sound energy flux) (W, P) sound power (sound energy flux) Sound energy passing through a certain area per unit time. The unit is watt, W. Note: 1. When the sound wave is a longitudinal wave, the acoustic velocity is expressed by the following formula: w --ds
wherein:
sound wave, Pa
the velocity of the particle in the direction of the surface area; s—area, n;
the half sound power (time average) of a plane or spherical wave passing through area 5 is W aa p*.$.coso/ot
+o
the time average of the effective sound pressure;
mass density, kg/m;
sound speed, m/a;
the product of the normal to the wave normal and the length of the new wave. 2.31 Acoustic irradiation dose is the total energy of acoustic irradiation to an object, which is the integral of the incident sound power and the acoustic irradiation dose. 2.32 Sound power (W) sound puwer of sound source The total energy emitted by the sound source in unit time, in watts (W). Acoustic radiation pressure (prcssurc) 2.33
The diameter caused by the echo radiation energy is still a constant pressure. 2.34
Spectrum (frequency spectrum) speetrum (frequency spectrum) The distribution graph of the components of the time function according to the amplitude or phase as the frequency: Note: Depending on the nature of the sound, its spectrum may be a linear spectrum, a continuous spectrum or a combination of both. 2.35 Line spectrum linesjectrun
A spectrum formed by some discrete frequency components
2.36 Continuus 5pectrum A spectrum containing continuous frequency components within a certain frequency range. 2.37 Spectral density 3pectrumdesitysspcetral When the density signal passes through an ideal filter and the filter bandwidth is close to zero, the mean square value per unit bandwidth is output, 2.38 power spectrum desity (PSD) random signal (t) The autocorrelation function of the Fourier transform is expressed as: S(u)
(1/2 yuan) /R(r).e-0t.dz
GB/T 39471996
The autocorrelation function of a function (
is proportional to the mean square spectral density (power), and the spectral desirability (mean square value of the time function per unit bandwidth) is; W(f) — 4#+S(a), = 2n
1 Power spectral density is used to measure various parameters of optical vibration, such as displacement, velocity, acceleration, etc. In the study of motion, power spectral density often refers to the power spectral density of acceleration (representing velocity).
2 If R(-) is the square correlation function of two time-dependent functions, then S(w) is the cross-power spectrum. 2.39 Vibration position (a) [vibratian] displacement The vector of the change in the position of an object relative to the reference coordinate of the beam. The unit is meter, m, 2.40_ Vibration velocity (vibration) velociuy The time rate of change of displacement, measured in meters per second. m/s. Dynamic acceleration) Lvibraliaareleralin2.41
The time rate of change of velocity, measured in meters per second squared, In/, 2.42 For example, velocity, jerk
The time rate of change of acceleration, measured in meters per second squared, In/, 2.43 Level
In acoustics, the logarithm of the ratio of a quantity to a similar reference quantity (rferuncouantiy). The base of the number, the reference quantity and the type of level should be stated.
The type of level is indicated by a name, such as point level, sound power level, etc. 1
2 The type of logarithm, the logarithmic base and the proportional band are different, and different units of the level are obtained, such as bel, fen, nare, etc. bel [erle (13) hel
The unit of the new level. When the logarithm of the ratio of a quantity to a similar reference quantity with a base of 10 is 1, it is called 1 Bel. It is represented by B. [The quantity comparable to power is
Let: The quantities comparable to power are: current square, pressure square, particle inverse force, city intensity, sound energy density, displacement square, velocity square, acceleration square, force square, and power, etc.,
2.45 decibel (αB) derihrl (d)
A unit of magnitude. When the logarithm of the ratio of a quantity to a similar reference quantity with a base of 10 is 1, it is called 1 decibel: It is represented by
1 dB=0.1 B, it is used for quantities comparable to power. Note: Products that can be compared with frequency include: current square, voltage square, particle velocity square, sound intensity, sound energy density, power square, velocity square, acceleration square, force square and power itself, etc. When using sound pressure, decibel is the unit of the square of the output pressure. The quotient is called the output pressure level. 2 decibel effective N is calculated according to the following formula:
N --10lg(W?/W) dB
-20lg(p./pr) dK
6 residual power (Np)neper
A unit of level. The logarithm of the ratio of a quantity to a similar reference quantity with e(2.718 28) as the base is 1 is called a 1 ratio. It is represented by N and is used for quantities that are not comparable with current or electricity. The applicable products are current, voltage, sound, force, particle displacement, particle velocity,Particle acceleration, the difference in the amount of force is: o = ntp/p)
31Np=8.686dB.
2.47 Sound pressure level (1) sound pressure level GB/T 3947-1996
The logarithm of the ratio of the sound bed to the reference sound pressure multiplied by 2 with a base of 10, the unit is negative [B]. But usually dB is used as the unit, and the reference sound must be specified.
: The standard sound pressure is:
, 20 μPa in air);
b.1μPa (water towel),
2.48 Sound intensity level (Lt) sound intensity levelThe logarithm to the base 10 of the ratio of the sound intensity to the reference sound intensity, in bels. But usually d is used as the unit. The reference sound intensity must be specified.
1 The reference sound intensity in air science is 1 pw/in. 2 Under the condition of traveling waves, the relationship between the sound pressure and the sound intensity level is fixed, and the sound intensity level can be calculated from the sound level. In this case, the relationship between the two is complicated, and the sound intensity level cannot be calculated from the sound level.
gSound power level (Zw)soundpowerlevel2.49
The logarithm to the base 10 of the ratio of the sound power to the reference sound power, in bels, B. But usually dB is used: The reference sound power must be specified.
Note, the base sound pressure is lpw,
2.50Sound levelsund level
The weighted sound pressure level measured with certain instrument characteristics and AB, C weighting characteristics. The instrument characteristics and weighting characteristics used must be specified, otherwise it refers to A sound level. The reference sound pressure must also be specified
The reference sound pressure is 20 μPa,
2A, B, double characteristics are 40, 70, 100 respectively and the counter line of equal loudness line: the calibration characteristics are represented by the letters before the sound level, A level es d,
2.51 Noise level naise level
The level of noise. Its type must be indicated by an attributive or contextual explanation, Note: The physical object measured (such as electricity), basic material, instrument and frequency bandwidth or other weighting should be specified: in the air, it is sound level. The weighting should be specified, otherwise it refers to A sound level. b.
2. 52 Band sound pressure suffix (Ipr) hand sound pressure level Sound pressure level in a limited frequency band. The reference sound pressure and bandwidth must be specified. Note: The standard sound pressure is 2 μPa. If the bandwidth is 1 octave, it is called the octave band sound pressure level, and so on.
2.53 Band sound power level (w) bandsoundpowerlevel Sound power level in a limited frequency band. The reference sound power and bandwidth must be specified. Note: The standard sound power is 1 pW. If the bandwidth is 1 octave, it is called the octave band sound power level, and so on.
2.54 Spectrum [lensity level (Ispcetrum "lensity" level) The logarithm of the ratio of the spectral density of a signal at a certain frequency to the reference spectral density with base 10, in bels, B. But it is usually expressed in dB. It is only applicable to signals with a continuous spectrum within the frequency range to be read. The spectral level is preceded by an appropriate adjective to indicate its type, such as sound pressure, speed, etc.
Note: If it is the effective sound pressure passing through the filter system, it is the reference sound pressure: / is the effective bandwidth of the filter, Af. is the reference width (1Hz). Then the sound pressure spectrum level
L-10l(*/20/(/a0]
-, - 10g(AF/4F3
2.55 [Vibration] Displacement level (1) [vibrationdisplacementlevel GB/T 3947 1996
The ratio of the displacement to the reference displacement with base 10 The base logarithm is multiplied by 2, and the unit is Bel". However, dB is usually used as the unit. The reference displacement must be specified:
Note: The reference displacement is 1 Pm
2.56 "Vibration|Velocity level (L,] [vibration] velocity level The logarithm of the ratio of velocity to the reference velocity to the base 10 multiplied by 2, and the unit is Bel. However, dB is used as the unit for the passband. The reference velocity must be specified,
non: The reference velocity is 1rm/s,
2.57 [Vibration velocity level (1) [vibration] accclcrationlevcl The logarithm of the ratio of acceleration to the reference acceleration to the base 10 multiplied by 2, and the unit is Bel]. However, dB is usually used as the unit. The reference acceleration must be specified.
Note: The left quasi velocity is 1 μm/s.
2.58 Oscillation + vibration A physical quantity changes continuously through maximum and minimum values during the observation time. Note: Oscillation is a general term. It refers to the physical oscillation of a mechanical system (including acoustic system) during the motion of the reference. 2.59 Excitation. Stimulus is an external force (such as suction or other input) applied to a device or system to make it respond in some way. Note: Excitation is a general term. When it acts on a person, it is called a normal stimulus. 2.60 The main frequency of a complex signal including many different frequency components. Note: In a driven system, the main frequency is the real frequency, while in general, music, etc., high-frequency signals, the main frequency is the fundamental frequency: 2.61 Fundamental frequency fundamental frequency. The frequency of a sinusoidal quantity with the same period as its period in synchronous oscillation. b. The lowest natural frequency of a vibration system.
2. 62 Frequency interval The distance between the frequencies of two sounds or other signals, expressed as the logarithm of the ratio of the higher frequency to the lower frequency. This logarithm is usually based on 2 and the unit is called the octave (ac1).
Note: The logarithm of the ratio is also based on 10 and the unit is called the decade. 2.63 octave
The distance between two sounds or other signals whose fundamental frequencies have a ratio of 2. 2.64 harmonic Lwave』
A sinusoidal wave with a frequency equal to an integer multiple of the fundamental frequency of a periodic oscillation. Note: For example, a wave with a frequency equal to twice the frequency is called a second harmonic, and a wave with a frequency equal to three times the frequency is called a third harmonic. 2.65
suhharmonic Lwave_
A sinusoidal wave with a frequency equal to an integer multiple of the fundamental frequency of a periodic oscillation. Juice: For example, the wave with a frequency equal to half of the fundamental frequency is called the second subharmonic, the wave with a frequency equal to one third of the fundamental frequency is called the second subharmonic, and so on. 6 Volume (volume) valuation (volume level) 2.66
The volume of a point in a circuit is the value of a complex audio signal measured at that point on a standard volume indicator. The volume of a signal is expressed in decimals,
2.67 Crest factor crest factor1
The ratio of the maximum value of a waveform to the effective value.
2. 68 Beat
The periodic change amplitude formed by adding simple harmonics of different frequencies and increases and decreases periodically according to the beat frequency. Distortion
The phenomenon of change in the signal waveform:
2.70 Reverb reverbcration
GB/T 39471996
a. b. The phenomenon that after the sound source stops making sound, the sound continues due to multiple reflections or scattering. b. The sound that continues due to multiple reflections or scattering after the sound source stops making sound. 2.71 Sound ech
Reflected sound or sound that returns due to other reasons, which is small enough and has a time difference large enough to be distinguished from the direct sound. Note: Sometimes it refers to reflection sound.
Efficiencyefficiency
The ratio of the useful output of the transferred or changed quantity to the total input: Note: When there is no special provision, efficiency refers to the efficiency of power. 2-73 [city] sireaming _acouslic_ sireaming _unidirectional flow caused by sound in the medium, 2.74 sound ray
The curve emitted by the sound source represents the direction of energy propagation. The wave nature of sound is ignored. Juice: In any solid medium, a sound line is a curve that represents the direction of the wave and is perpendicular to the liquid surface. 2.75jti beam [soundl] beam
directivity causes the sound energy radiated by the sound source to be concentrated in a certain place to form a beam-shaped sound wave: 2.76 Sound channel
A layer of medium that limits the propagating sound wave energy within a certain depth or altitude range in the ocean or in the air and prevents it from escaping. 2.77 Acoustic emission
The transient elastic wave produced by the rapid release of energy inside the material. Energy released inside the material is caused by external stress. 2.78 Kaiser effect Kaiser effect The transient characteristic of the acoustic emission phenomenon of certain materials under stress. If the material is subjected to two stresses successively and the second stress does not exceed the first, there will be little or no acoustic emission in the second time. 2.79 Acoustic fatigue
The phenomenon of rupture of crystalline solids under the action of strong fluctuating pressure. Note: The consequence of acoustic fatigue is the destruction or de-excitation of light structures and installed equipment (sometimes also liquid). 2.B0 fatigue life
The number of stress or strain cycles required for fatigue fracture of a material under cyclic loading (such as noise). Note: For actual parts, it is often used as a subtotal
2.81 SN curve
The relationship curve between the applied stress level 5 and the fatigue life N obtained based on the fatigue strength test data of the material. In acoustic fatigue tests, the acoustic fatigue performance curve of the material is often drawn with the sound pressure level instead of the stress level S. 2.82 shadow region (shadow zone) The area that the sound line cannot reach due to obstacles or refraction: 2.83 intensity The rapid and regular change of fluctualian intensity in a short time. Note: The cause of the change is the slight change of the normal vibration of the sound source in the room, or the many inhomogeneities in the atmosphere or the air. Short time refers to one second or less. 2.B4 Doppler effect Dopplereffect
The phenomenon of the observed frequency changing due to the change of the effective propagation distance between the source and the observation point in the transmission system.
Note: Although the fixed The relationship is as follows:
Ff(1+c3/(u/c)
Wujin:
Observed peak frequency + IIz;
Frequency of the source. H2: \
GB/T3947—1996
Velocity component of the source from the observation point to the source (and relative to the medium), m/%Velocity component of the source from the observation point to the observation point (relative to the medium) -1Ⅱ/B; - the speed of sound in a stationary medium, /;
, the difference between and is the Doppler shift (Doppler shill). 2.85 Weighting
A method of transforming a signal. The basic point is to emphasize certain components of the signal and suppress other components of the signal. The different proportional factors multiplied by the undesirable components of the signal are called weighting functions. 2.86 Weighting network
An electrical network designed according to the weighting function to achieve the purpose of the desired transformation of the signal. 2-87 Acoustic malfunctionA phenomenon in which an instrument or device becomes temporarily or permanently unusable under the fluctuating pressure generated by strong waves. 3 Vibration and mechanical shock
3-1 Steady-state The physical quantity of a vihration system is a periodic quantity.
3.2 Dynamic vibration Rising vibration
Vibration caused by transient excitation,
3.3 Forced vibration Forced vibration
Vibration forced by external excitation, such as periodic and continuous, forced vibration is steady-state vibration. 3.4 Free vibration Free vibration
Vibration when forced vibration does not exist.
3.5 Self-induced vibration (self-induced vibration) Vibration generated by the source of oscillatory excitation in a mechanical system but converted into vibratory excitation in the system. 3.6 Simple harmonic vibration Sinmple harmonic vibratian Vibration whose displacement, velocity or acceleration is a sinusoidal function of time, is a simple case of periodic vibration. 3.7 Resonance
When a system is forced to vibrate, any small frequency change of the excitation reduces the response. : The response may be a change in displacement, velocity or acceleration. When the reported frequencies are different, it is possible that the vibration type should be specified. 3.8 antiresonance
The phenomenon that any small frequency change of the excitation increases the response of a system in forced vibration. Note: The source of the response may be displacement, velocity or acceleration. When the reported frequencies are different, it is possible that the vibration type should be specified. 3.9 clamping
The phenomenon that energy is lost with time or distance. 3.10 viscous damping
The energy loss caused by the resistance of the particle motion in a vibrating system, which is proportional to the velocity of the particle and opposite to the direction. 3.11 equivalent viscous damping is the viscous damping assumed in the analysis of a vibrating system. The energy loss caused by it in the vibration is the same as the loss caused by the actual damping.
3.12fL Friction damping dryfrietion damping·Caulonbdatmping Energy loss caused by the resistance of fixed magnitude, independent of the velocity of the mass point and in the opposite direction in the vibration system. 3.13 Nonlinear damping nonlineardamping Damping force is not proportional to the velocity. 3.14 Critical damping critical damping GB/T3947—1996
The minimum damping required to restore a moved system to its original position without oscillation. Damping ratio
In a system with only viscous damping, the ratio of the actual damping of the system to the critical damping: Damping coefficient (e) dampingcoefficicnt3.16
If a certain quantity is a function of time:
F(t) = Ae e -,ainlo(fto))
Where: ——damping coefficient, in units of seconds, -3.17 Time constant () time constan1The time required for the amplitude of a quantity that decays exponentially to decay to 1/e times the amplitude at a specified time. It is the reciprocal of the damping coefficient, in units of seconds, \.
3. 1B Quality factor, Q factorA measure of the sharpness or selectivity of a single-degree-of-freedom mechanical or electrical system. Note
" In mechanical systems, this value is equal to half the reciprocal of the H ratio, 2This value is also called the common amplification factor.
3.19 Logarithmic reduction rate (4) logarithmic reduction rate is the natural logarithm of the ratio of two adjacent amplitudes with opposite signs in the decay of a single frequency vibration, with the unit of neper.NP. The logarithmic reduction rate is equal to the product of the damping coefficient and the period (A=-T: sometimes also used as the unit of.1-0.!15p
3.20 Transmission ratio, trinsfer tiotransmissihiliy The dimensionless ratio of the response amplitude to the excitation amplitude of a vibration system under steady-state vibration. The transmission ratio can be the ratio of force, displacement, velocity or acceleration.
critical speed critical speed
The rotation speed corresponding to the resonant frequency of the rotating system, the degree of degrce of frredom
The minimum number of independent generalized coordinates required to completely determine the position of each part of a mechanical system at any time. It is generally equal to the number of possible independent generalized displacements. Normal mode of vibration" Normal wave normal motion of vibration 323
A natural mode of vibration of a vibrating or waving system: it is characterized by a certain stationary or stationary state in a certain coordinate system. Any complex motion of a system can generally be decomposed into a sum of normal vibrations. The frequency of normal vibrations is not the normal frequency (normal frequency).
3.24 Natural frequency
The frequency of a system when it is in natural vibration. In a multi-degree-of-freedom system, the natural frequency is the normal frequency. 3.25
Undamped natural frequency The free vibration frequency of a mechanical system formed only by the elastic force and inertia of the system. 3.26 Damped natural frequency The vibration frequency of a mechanical system with an elastic force. 3.27 Vibration isolation The use of elastic supports to reduce the energy of the system's response to external excitation. In a steady state, vibration isolation is expressed as the inverse of the transfer ratio. 3.28 Vibration isolatorwwW.bzxz.Net
An elastic support that isolates the system from steady-state excitation. 3-29 Dynamic vibration absorber GR/T 39471996
A device that transfers energy to an additional resonant system tuned to the vibration frequency to reduce the vibration of the original system. The reaction force of the additional system is inverse to the force applied to the original system.
3.30 Machine balancing
Adjust the mass balance of the rotor to reduce or control the vibration force on its sleeve or bearing. 3.31 Mechanical shock [mechanical shock] A transient motion in a mechanical system. It is accompanied by a non-periodic sudden change in force, displacement, velocity or acceleration. Method: The meaning of sudden change is that the change time is faster than the period of the inherent vibration of the system. 3.32 Shock pulse shock pulse
A major disturbance in which the acceleration rises from a constant value and then decays in a short period of time. Shock pulses are generally expressed in a graph by taking acceleration as a fraction of time
Note: Short time means a period that is much shorter than the inherent duration. 3.33 Duration of shock pulses The time required for the acceleration of the pulse to rise from a certain specified fraction of the maximum value and then decay to the same value. The specified fraction should be as stated in the instructions
Note: The specified fraction is usually 1/10 of the peak value or 20dB lower. 3. 34 Pulse rise time Pulse rise time The time required for a pulse to rise from a specified small fraction of the maximum amplitude to a specified large fraction. The small fraction and the large fraction are explained by
: The small fraction and the large fraction are usually taken as 1/109/10 respectively. Velocity shock
A mechanical shock caused by a sudden change in the velocity of the entire system. 3. 36 Shock spectrum shock spertrum (shuck response specirum) The response of a single-degree system under an external shock, expressed as a distribution graph of amplitude or phase as a function of frequency. The maximum amplitude is related to the resonant frequency of the system,
Note: The response can be absolute displacement, relative displacement, absolute velocity, phase or acceleration, collision, impact impulse
The impact of a moving mass on another moving or stationary mass. impulse
The product of force and the time of action. If the force is a function of time (t). It is in! : before and after is zero, then the impulse is: f)dt
4 Sound waves
4.1 Waves A disturbance propagating in a medium. At any point in the medium, the quantity measuring the disturbance is a function of time, and at any moment, this quantity at any point is a function of its position:
Any physical quantity that has a spatial and temporal dependence on the propagating disturbance is also called a wave in space at the same moment. 4.2 Longitudinal wave
A wave in which a particle in the medium moves along the direction of propagation. 4.3 Transverse wave
A wave in which a particle in the medium moves perpendicular to the direction of propagation: 4.4 Progressive wave A wave propagating in a uniform and homogeneous medium without boundaries.
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