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Noise & Vibration Control MCQ

What is the definition of Probabilistic Vibration?

Answer

Correct Answer: Vibration with a magnitude that can only be predicted on a statistical basis.

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What is the magnitude of probabilistic vibration?

Answer

Correct Answer: Cannot be predicted on a statistical basis

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What is the meaning of "platform" in MIL-STD-810?

Answer

Correct Answer: Any vehicle, surface, or medium that carries a piece of equipment.

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What is a platform?

Answer

Correct Answer: Any vehicle, surface, or medium that carries a piece of equipment

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What is a piezoresistive transducer?

Answer

Correct Answer: A transducer with an electrical output that depends on the deformation of its semiconductor resistive element

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Which of the following is true about a piezoresistive transducer?

Answer

Correct Answer: It offers greater resistance to change than the wire of a strain-gauge transducer for a given deformation.

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What is the fractional part of a period called?

Answer

Correct Answer: Phase

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Which of the following is a characteristic of performance-based requirements?

Answer

Correct Answer: They describe what the product should do.

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What is a patent defect?

Answer

Correct Answer: A flaw in and/or the workmanship of a part or assembly that has failed under a test or screen.

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What is an orbit?

Answer

Correct Answer: The path of a shaft centerline during rotation

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What is a precomputed drive signal in open-loop control?

Answer

Correct Answer: A signal that is computed before it is sent to the system.

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What is Open-loop control?

Answer

Correct Answer: Precomputed or preconceived drive signals without modifying or refining the signals based on observation of the resulting motion.

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What is the control of a computer's data sampling rate called?

Answer

Correct Answer: Order tracking

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What does operational limit refer to?

Answer

Correct Answer: The extremes beyond which a product is not expected to operate.

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What is an octave?

Answer

Correct Answer: The interval between two frequencies differing by exactly 2:1

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What is the interval between two frequencies differing by exactly 2:1 called?

Answer

Correct Answer: Octave

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What is the definition for nonlinearity?

Answer

Correct Answer: The deviation from a best fit straight line of the true output versus the actual value measured.

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What is an undamped system's natural frequency also known as?

Answer

Correct Answer: The frequency of the normal modes of vibration.

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What is the natural frequency of an undamped system's free vibration?

Answer

Correct Answer: It is the frequency of the system's normal modes of vibration.

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What is the purpose of notching?

Answer

Correct Answer: To prevent unnecessary excitation of any large resonances that may occur during a vibration test.

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What is the noise floor?

Answer

Correct Answer: The summation of all noise sources and unwanted signals within a measurement system.

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What is the definition of natural environment?

Answer

Correct Answer: Conditions that occur in nature and are not caused by equipment

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What is a mission profile?

Answer

Correct Answer: Time-phased description of the events and environments an item experiences from initiation to completion of a specified mission.

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One micron is equal to _______.

Answer

Correct Answer: 10-6 meters

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How many microns are in one inch?

Answer

Correct Answer: 254000

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What is mechanical failure?

Answer

Correct Answer: A malfunction consisting of cracking, excessive displacement, misalignment, loosening, etc.

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What is the mean?

Answer

Correct Answer: A value intermediate between quantities under consideration

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What is Machinery health monitoring?

Answer

Correct Answer: The measurement, recording, and analysis of machinery parameters to determine machinery health.

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What is the other name for lateral sensitivity?

Answer

Correct Answer: Cross-axis sensitivity

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What is Lateral sensitivity?

Answer

Correct Answer: Sensitivity of a sensor in a direction perpendicular to the sensitive axis.

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What is liquid nitrogen's chemical formula?

Answer

Correct Answer: LN2

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What is a life unit?

Answer

Correct Answer: A measurement of an item's use duration

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What does the life unit measurement include?

Answer

Correct Answer: Time, cycles, distance, rounds fired, attempts to operate, etc.

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The logarithm is normally base ____.

Answer

Correct Answer: 10

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What is a latent defect?

Answer

Correct Answer: A flaw in a part, assembly, and/or workmanship that is dormant but can result in failure.

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What is a keyphasor?

Answer

Correct Answer: A signal generated by a sensor that observes a once-per-revolution event

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What is the rate of change of acceleration with time called?

Answer

Correct Answer: Jerk

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What does intensity measure?

Answer

Correct Answer: The severity of vibration or shock

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What is the input impedance?

Answer

Correct Answer: Shunt resistance and capacitance/inductance measured at the input terminals

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What is another term for "inertially-referenced motion"?

Answer

Correct Answer: Free space

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A sensor that measures motion referenced to a fixed point in space is what?

Answer

Correct Answer: Inertially-referenced

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What is an impulse?

Answer

Correct Answer: The integral of force over a time interval.

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What is the cause of imbalance?

Answer

Correct Answer: The unequal distribution of weight or mass on a rotor

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What is the unequal distribution of weight or mass on a rotor called?

Answer

Correct Answer: Imbalance

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What is hash?

Answer

Correct Answer: A distortion in a signal

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What is a hard failure?

Answer

Correct Answer: When a product under test ceases to work correctly and does not resume correct operation.

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What does a haversine pulse look like?

Answer

Correct Answer: A sine wave

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What is harmonic distortion?

Answer

Correct Answer: A distortion in an output signal caused by the presence of frequencies not present in the input signal

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What does HALT stand for?

Answer

Correct Answer: Highly Accelerated Life Test

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What does the acronym HALT stand for?

Answer

Correct Answer: Highly accelerated life tests

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What is the value for 1 gravitational unit?

Answer

Correct Answer: 9.80665 m/s²

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How many gals are equivalent to 1g?

Answer

Correct Answer: 980.6

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What is the acceleration represented by the unit gal?

Answer

Correct Answer: 1 cm/sec²

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What is the main cause of a ground loop?

Answer

Correct Answer: Voltage drops between the two ground connections

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What are ground loops caused by?

Answer

Correct Answer: A signal source and a signal measurement device being grounded at two separate points on a ground bus.

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What does graduation mark mean?

Answer

Correct Answer: The scale intervals on a measuring instrument

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What does the PSD measure?

Answer

Correct Answer: The signal is measured in acceleration using the gravitational constant G.

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What are the units of PSD?

Answer

Correct Answer: G2/Hz

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What is FEA?

Answer

Correct Answer: A computer-aided design technique for predicting the dynamic behavior of a mechanical system.

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What does the definition of MTBF stand for?

Answer

Correct Answer: Mean Time Between Failures

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What is the definition of failure?

Answer

Correct Answer: Failure is the event or inoperable state in which any item or component does not perform as previously specified.

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What is the goal of environmental stress screening?

Answer

Correct Answer: Precipitate latent defects into recognizable failures

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When is an eddy current generated?

Answer

Correct Answer: When a conductive material intercepts the electromagnetic field of a displacement or proximity probe

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What are equal loudness curves?

Answer

Correct Answer: Graphs of pure tone sound pressure levels versus frequency.

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What is the meaning of the word "environment"?

Answer

Correct Answer: The aggregate of all external and internal conditions that influence the form, performance, reliability, or survival of an item.

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What is environment defined as?

Answer

Correct Answer: An aggregate of all external and internal conditions that influence the form, performance, reliability, or survival of an item.

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What is mechanical eccentricity?

Answer

Correct Answer: A variation of the shaft surface radius when referenced to the shaft’s true geometric centerline.

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What is distortion in electronics?

Answer

Correct Answer: Any unwanted signal

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In which field is distortion defined as any unwanted signal?

Answer

Correct Answer: Electronics

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What is accomplished by multiplying the velocity signal by jΩ in a computer?

Answer

Correct Answer: Representation in terms of time rate of change.

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What does differentiating velocity yields?

Answer

Correct Answer: Acceleration

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What is the number of DOF?

Answer

Correct Answer: The number of values in the final calculation of a statistic that are free to vary.

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What is the number of directions of motion on a structure?

Answer

Correct Answer: Degrees of freedom

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What is the main purpose of damping?

Answer

Correct Answer: To dissipate oscillatory or vibratory energy

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What is the definition of damping?

Answer

Correct Answer: The dissipation of oscillatory or vibratory energy with motion or with time.

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What is a digital-to-analog converter?

Answer

Correct Answer: A device that converts a digital signal into an analog voltage

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What is the reciprocal of stiffness?

Answer

Correct Answer: Compliance

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What does compliance describe?

Answer

Correct Answer: Displacement divided by force

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What is the purpose of closed-loop control?

Answer

Correct Answer: To refine or modify drive signals to bring responses closer to desired motions.

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What is chatter?

Answer

Correct Answer: An event that can occur in response to shock vibration

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What is a sensor?

Answer

Correct Answer: A device that converts a physical quantity, such as light intensity or pressure, into an electrical signal

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What does calibration mean?

Answer

Correct Answer: The process of adjusting the measured voltage and frequency readings based on a precise internal reference voltage.

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What is the primary purpose of a barrier?

Answer

Correct Answer: To block airborne sound from entering the passenger compartment

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What is the purpose of a bounce test?

Answer

Correct Answer: To assess the effect of vibration on unrestrained cargo

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What does bias refer to?

Answer

Correct Answer: A more or less persistent tendency for a group of measurements to be too large or too small.

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What is the unit of measurement for bandwidth?

Answer

Correct Answer: Hz

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What is a sound exemplified by loose power transformer laminations?

Answer

Correct Answer: Hum

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What is the power frequency in Hz of a sound exemplified by loose power transformer laminations?

Answer

Correct Answer: 60

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What is the definition of broadband?

Answer

Correct Answer: Vibration or other signals that are unfiltered.

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What does broadband refer to?

Answer

Correct Answer: Signals at all frequencies contribute to the measured value.

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What does a bode plot display?

Answer

Correct Answer: Magnitude of vibration at 1x the shaft speed and its phase relative to the shaft position

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What is a bode plot?

Answer

Correct Answer: A graph of magnitude and phase plotted against speed.

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What is a baseline spectrum?

Answer

Correct Answer: A vibration spectrum that is recorded when a machine is in good working condition.

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What is the term for the process of adjusting the distribution of mass in a rotating element to reduce vibratory forces generated by rotation?

Answer

Correct Answer: Balancing

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What is balancing?

Answer

Correct Answer: The process of adjusting the distribution of mass in a rotating element to reduce vibratory forces generated by rotation.

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What is the meaning of "Axial?"

Answer

Correct Answer: The direction along the centerline of a shaft.

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What is the average value of a pure sine wave?

Answer

Correct Answer: Zero

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What does a power spectral density plot show?

Answer

Correct Answer: A spectral display of the power (voltage squared) at each frequency.

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What does an anti-aliasing filter do?

Answer

Correct Answer: It stops frequencies higher than some fraction of the sample rate to minimize aliasing.

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What is an anti-aliasing filter?

Answer

Correct Answer: A low-pass filter designed to stop frequencies higher than some fraction of the sample rate to minimize aliasing.

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What does Amplitude refer to?

Answer

Correct Answer: Displacement, velocity, acceleration, voltage, current, force, or pressure.

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What is amplitude?

Answer

Correct Answer: The magnitude of a quantity's variation from its zero value

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What causes aliasing in a spectrum?

Answer

Correct Answer: Sampling data at too low a sampling frequency

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What is aliasing?

Answer

Correct Answer: A spectrum analysis problem that results from sampling data at too low a sampling frequency.

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What is accessibility?

Answer

Correct Answer: Accessibility measures the related ease of access to various portions of an item for operation or maintenance.

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Accessibility is the related ease of what to various portions of an item?

Answer

Correct Answer: Access

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What is accelerated stress testing?

Answer

Correct Answer: A post-production process on a sample of units to precipitate hidden or latent failures.

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What is the main purpose of accelerated stress testing?

Answer

Correct Answer: To precipitation hidden or latent failures.

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Seismic sensors measure _____ vibration.

Answer

Correct Answer: Absolute

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What is absolute vibration?

Answer

Correct Answer: Vibration of an object relative to a fixed point in space.

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What changes an analog signal into a digital signal?

Answer

Correct Answer: A digital converter

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What is an analog signal?

Answer

Correct Answer: A signal that changes in voltage or current

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What is the process of summing and dividing several like measurements to improve accuracy or lessen the effect of any asynchronous components called?

Answer

Correct Answer: Averaging

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What is the degree to which an item is in an operable and committable state at the start of a mission called?

Answer

Correct Answer: Availability

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What does an angular rate sensor measure?

Answer

Correct Answer: Rotational velocity (degrees or radians per second) around its sensitive axis.

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What is the ambient environment?

Answer

Correct Answer: The conditions that characterize the air or other medium that surrounds the material.

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What is the purpose of an aggravated test?

Answer

Correct Answer: To reduce test time or assure a margin of safety.

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What is an accelerometer?

Answer

Correct Answer: A sensor, transducer, or pickup that converts acceleration into an electrical signal.

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What are the two common types of accelerometers?

Answer

Correct Answer: Piezoresistive and Piezoelectric

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What is the purpose of accelerated life testing?

Answer

Correct Answer: To identify failure-prone, marginally strong elements by causing them to fail.

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What is the meaning of traceable to NJST?

Answer

Correct Answer: A measure of the uncertainty of an instrument reading compared to that of a primary standard

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What is the goal of equalization?

Answer

Correct Answer: To compensate for the non-flat frequency response of human hearing

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What is the axial position?

Answer

Correct Answer: The change in a rotor's position or displacement along its axis and relative to a fixed point nearby.

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What is another name for average responding?

Answer

Correct Answer: Mean responding

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What is the average responding proportional to?

Answer

Correct Answer: The average of the absolute values of all input waveforms

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Auto-ranging is the capability of an instrument to switch ranges automatically. True or False?

Answer

Correct Answer: True

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What does auto-ranging refer to?

Answer

Correct Answer: The capability of an instrument to switch ranges automatically.

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What is the square root of the area under the ASD curve defined as?

Answer

Correct Answer: G RMS of acceleration

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What does ASD stand for?

Answer

Correct Answer: Spectral Density

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What is the frequency in Hz of a 10 rad/s angular frequency?

Answer

Correct Answer: 160 Hz

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What is the torsional vibration frequency in radians per second?

Answer

Correct Answer: Angular frequency

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Which of the following is NOT a desired machinery condition of alignment?

Answer

Correct Answer: Least vibration

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What is the desired machinery condition when the axes of a machine's components are adjusted to be colinear, parallel or perpendicular?

Answer

Correct Answer: Alignment

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What is the relationship between accuracy and inaccuracy?

Answer

Correct Answer: Accuracy is not related to inaccuracy.

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What is acceleration?

Answer

Correct Answer: The rate of change of velocity with time

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What is the rate of change of velocity with time called?

Answer

Correct Answer: Acceleration

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How does an absorber work?

Answer

Correct Answer: By converting vibration to heat

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What is an absorber?

Answer

Correct Answer: A device capable of reducing or attenuating vibration

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What does the term "absolute" refer to in calibration?

Answer

Correct Answer: Calibration based on the primary standards of mass, length, and time

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How do 6DOF machines produce vibration?

Answer

Correct Answer: They use air-driven impact hammers to excite a vibrating plate or table

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