From ASTM E 610-82
ACOUSTIC EMISSION (AE) - the class of phenomena whereby transient elastic waves are generated by the rapid release of energy from a localized source or sources within a material, or the transient elastic wave(s) so generated.
ACOUSTIC EMISSION is the recommended term for general use. Other terms that have been used in AE literature include (1) stress wave emission, (2)micro-seismic activity, and (3) emission or acoustic emission with other qualifying modifiers.
ACOUSTIC EMISSION COUNT (Emission Count) (N) - the number of times the
acoustic emission signal amplitude exceeds a preset threshold during any selected portion of a test.
ACOUSTIC EMISSION COUNT RATE (Emission Rate or Count Rate) (N) - the time rate at which emission counts occur.
ACOUSTIC EMISSION EVENT ENERGY - the total elastic energy released by an emission event.
ACOUSTIC EMISSION EVENT (Emission Event) - a local material change giving rise to acoustic emission.
ACOUSTIC EMISSION SENSOR - a detection device, generally piezoelectric, that transforms the particle motion produced by an elastic wave into an
electrical signal.
ACOUSTIC EMISSION SIGNAL (Emission Signal) - an electrical signal obtained by detection of one or more emission events.
ACOUSTIC EMISSION SIGNAL AMPLITUDE - the peak voltage of the largest
excursion attained by the signal waveform from an emission event.
ACOUSTIC EMISSION SIGNATURE (Signature) - a set of identifiable
characteristics of acoustic emission signals associated with a specific test article as observed with a particular instrumentation system under specified test conditions.
ACOUSTIC EMISSION WAVEGUIDE - a device that couples elastic energy from a structure or other test object to a remotely mounted sensor during AE
monitoring. An example of an acoustic emission waveguide would be a solid wire or rod that is coupled at one end to a monitored structure, and to a sensor at the other end.
ARRIVAL TIME INTERVAL (delta t) - the time interval between the detected arrivals of an acoustic emission wave at the ith and jth sensors of a sensor array.
BURST EMISSION - a qualitative description of the discrete signal(s) related to individual emission event(s) occurring within the material. Use of the term BURST EMISSION is recommended only for describing the qualitative appearance of emission signals.
CONTINUOUS EMISSION - a qualitative description of the sustained signal
level produced by rapidly occurring acoustic emission events. Use of the term CONTINUOUS EMISSION is recommended only for describing the qualitative appearance of emission signals.
COUPLANT - a material used at the structure-to-sensor interface to improve the transmission of acoustic energy across the interface during acoustic emission monitoring.
CUMULATIVE (ACOUSTIC EMISSION) AMPLITUDE DISTRIBUTION F (V) - a display of the number of times the acoustic emission signal exceeds an arbitrary amplitude as a function of amplitude (V).
CUMULATIVE (ACOUSTIC EMISSION) THRESHOLD CROSSING DISTRIBUTION Fe (V) - the number of times the acoustic emission signal exceeds an arbitrary threshold as a function of the threshold voltage (V).
dB SCALE - a relative logarithmic scale of signal amplitude defined by dB Vo = 20 log V/Vo. The reference voltage is defined as 1mV out of the sensor and V is the measured amplitude in volts. Additional x 100 gain preamplifier.
DIFFERENTIAL (ACOUSTIC EMISSION) AMPLITUDE DISTRIBUTION f (V) - a display of the number of times the acoustic emission signal peak amplitude falls between amplitudes V and V + delta V as a function of the amplitude V. f (V) is the absolute value of the differential of the cumulative amplitude distribution F (V).
DIFFERENTIAL (ACOUSTIC EMISSION) THRESHOLD CROSSING DISTRIBUTION ft (V) - the number of times the acoustic emission signal waveform has a peak between thresholds V and V + DV as a function of the amplitude V. f (V) is the absolute value of the derivative of the cumulative amplitude distribution F(V).
ELECTRONIC WAVEFORM GENERATOR - a device which can repeatably induce a
transient signal into an acoustic emission processor for the purpose of
checking, verifying, and calibrating the instrument.
EVENT COUNT (Ne) - the number obtained by counting each discerned acoustic emission event once.
EVENT COUNT RATE (Ne) - the time rate of the event count.
EXAMINATION AREA - the part of a structure under test which is monitored with AE.
KAISER EFFECT - the absence of detectable acoustic emission at a fixed
sensitivity level, until previously applied stress levels are exceeded.
LOGARITHMIC (ACOUSTIC EMISSION) AMPLITUDE DISTRIBUTION g (V) - the number of acoustic emission events with signal amplitudes between V and aV (where a is a constant multiplier as a function of the amplitude. This is a variant of the differential amplitude distribution, appropriate for logarithmically windowed data.
MEASURED AREA OF THE RECTIFIED SIGNAL ENVELOP (MARSE) - a measurement of the area under the envelope of the rectified linear voltage time signal from the sensor.
MULTI-CHANNEL SOURCE LOCATION - a source location technique, which relies on the stress wave from a single source producing, hits at more than one sensor. Position of the source is determined by mathematical algorithms using difference in time of arrival.
RELEVANT INDICATION - (in nondestructive examination) an indication
requiring evaluation.
RING-DOWN COUNT - see ACOUSTIC EMISSION COUNT, which is the preferred term.
SENSOR HIT (HIT) - the detection of a stress wave by a single sensor.
NOTE - An AE source may produce hits at several sensors, which are close enough to detect the stress wave.
SIMULATED AE SOURCE - a device which can repeatedly induce a transient
elastic stress wave into the structure.
STIMULATION - any action of applying a stimulus such as force, pressure, heat, etc., to a test article to cause activation of existing acoustic emission sources.
SYSTEM EXAMINATION THRESHOLD - the electronic instrument threshold above which data will be detected. System examination threshold may be lowered below the evaluation threshold at the discretion of the operator.
THRESHOLD OF DETECTABILITY - a peak amplitude measurement used for cross calibration of instrumentation from different vendors.
ZONE - the area surrounding a sensor from which AE sources can be detected.
ZONE LOCATION - a method of locating the approximate source of emission.