How Areal Heterogeneities Affect Pulse-Test Results

1970 ◽  
Vol 10 (02) ◽  
pp. 181-191 ◽  
Author(s):  
Saul Vela ◽  
R.M. McKinley
Keyword(s):  
Time Lag ◽  
Pulse Amplitude ◽  
Test Results ◽  
Hydraulic Diffusivity ◽  
Pulse Test ◽  
Influence Area ◽  
Pulse Testing ◽  
And Storage ◽  
Degree Of Heterogeneity ◽  
Relative Variability

Abstract Reservoir transmissibility and storage values can be obtained from pressure pulses induced in one well and measured at a second well. Such pulse-test values are generally calculated from pulse-test values are generally calculated from equations which assume the formation is homogeneous. This paper examines the effects of areally distributed heterogeneities on pulse-test values. An influence area is first developed for a pulse-tested well pair; only those heterogeneities pulse-tested well pair; only those heterogeneities within this area significantly affect pulse-test results. Next, for three limiting cases, the manner in which a pulse test averages heterogeneities within the influence area is described. These are the cases for which one of the three formation properties - hydraulic diffusivity, transmissibility properties - hydraulic diffusivity, transmissibility and storage - is constant throughout the influence area. Finally, a method called directional correction is developed that when applied to pulse-test values of transmissibility and storage restores some, if not most, of the true degree of heterogeneity to these values. Accuracy of the method depends upon the relative variability of the true values. Introduction The pulse-testing method of Johnson et al. uses a sequence of rate changes at one well to create a low-level pressure interference response at an adjacent well. This response is readily analyzed for reservoir properties if one assumes an infinite, homogeneous reservoir model. The field data of McKinley et al. show that, despite the use of a simple analytical model, pulse-test values are sensitive to between-well pulse-test values are sensitive to between-well formation properties. Calculated values for transmissibility and storage exhibit considerable variation with direction around a central pulsing well. These values cannot, however, reflect the exact degree of heterogeneity since flow about the pulsing well is usually nonradial. pulsing well is usually nonradial. This paper examines the effects of certain idealized types of areal heterogeneities on pulse-test values calculated from the simple model. In pulse-test values calculated from the simple model. In particular, an influence area for a pulse-tested well particular, an influence area for a pulse-tested well pair is first developed. This area is defined as that pair is first developed. This area is defined as that areal portion of the formation whose properties determine the numerical value, obtained from pulse testing the well pair. Its size depends on the length of the pulse and the hydraulic diffusivity of the formation. We then determine the type of average values yielded by a pulse test when heterogeneities are distributed randomly throughout the influence area. Results of these studies provide a simple correction scheme that restores some of the true degree of heterogeneity to pulse-test values of transmissibility and storage. Accuracy of the method depends on the relative variability of the latter two reservoir parameters. PULSE-TEST TERMINOLOGY AND ANALYSIS PULSE-TEST TERMINOLOGY AND ANALYSIS A typical rate-change sequence at the pulsing well appears at the bottom of Fig. 1. The pulse rate is q reservoir B/D and the pulse length is delta t minutes. The time between pulses is R delta t minutes. Each such pulse cycle induces at the responding well the pressure response (pulse) shown at the top of Fig. 1. According to the analysis method of Johnson et al., each pressure pulse is characterized by two quantities - a time lag, tL minutes, and a pulse amplitude, delta p psi. How these values are pulse amplitude, delta p psi. How these values are determined from the pressure response is apparent from Fig. 1. For an infinite, homogeneous formation, the time lag, tL, the R-value and the well spacing, rws, are sufficient to determine the hydraulic diffusivity, of the formation. These values, coupled with pulse amplitude, p, and pulse rate, q, determine formation transmissibility, =kh/ . Formation storage, = ch, is obtained from the ratio = / . Charts to facilitate this analysis are given by Brigham for R=1. SPEJ P. 181

A Method To Account for Afterflow at the Pulsing Well During Pulse Tests

1983 ◽  
Vol 23 (03) ◽  
pp. 519-520
Author(s):  
Hubert Winston
Keyword(s):  
Computer Simulations ◽  
Flow Rate ◽  
Storage Capacity ◽  
Pulse Length ◽  
Test Area ◽  
Pilot Test ◽  
Test Results ◽  
Pulse Test ◽  
Wellbore Storage ◽  
And Storage

Abstract The nature of wellbore storage is such that afterflow during a pulse test can affect the reservoir pressure performance and can lead to the calculation of erroneous performance and can lead to the calculation of erroneous values for formation transmissibility and storage. This is most likely to occur when the wells of interest are close together or when after flow persists for a long time relative to the pulse length. This article describes a technique that was developed to account for the effects of after flow at the pulsing well during pulse testing of a small production pilot. The technique is not general because it requires that a computer-generated simulation of each pulse test be made. An application of the method is given. Introduction In carrying out a pulse test, we introduce a pressure disturbance into a reservoir by alternately increasing and decreasing the flow rate at the pulsing well in a known manner. The pressure at the responding well is monitored, and, if the wells are in pressure communication, the pressure distrubance eventually will affect the pressure at the responding well. Since the form and the duration of the flow, rate disturbance are known, and since the mathematics that describe the pressure behavior of fluid-beefing reservoirs are well understood, the pulse test pressure response can be predicted. Several methods are available to calculate values for formation transmissibility and storage within a pulse-tested reservoir. Although all real reservoirs are heterogeneous, the models for deriving these techniques assume that the reservoir is ideal. When the wells of interest are far apart or when the duration of after flow is short relative to the pulse length, the effects of wellbore storage on the pulse test results will be slight. If, on the other hand, the pulsing well and the responding well are close together or if after flow persists for a tong time, the effects of wellbore storage on the pulse test results may be substantial. The work described here began during the analysis phase of a series of pulse tests that were run in a small phase of a series of pulse tests that were run in a small pilot test area. Computer simulations of the tests showed pilot test area. Computer simulations of the tests showed that the method of Mondragon and Menzie would not compensate adequately for the strong effects of after flow on test results. Description of the Method Since a series of injection/falloff tests had been run in the pilot area, it was possible to obtain values for the ratio of formation transmissibility to the wellbore storage capacity, /F, at each well by type-curve matching techniques. Using this parameter, we can determine the after flow vs. time profiles that would occur during the pulsing-well shut-in periods and incorporate them into a computer simulation of each pulse test. A typical pulsing well-flow profile showing after flow during the shut-in period is profile showing after flow during the shut-in period is illustrated in Fig. 1. Given that the pulsing wells were observed to go on vacuum soon after shut-in and given that the wellbore storage capacity for these wells during the on-vacuum condition should be approximately two orders of magnitude larger than it would be during injection SPEJ p. 519

Pulse-Test Response of a Two-Zone Reservoir

1970 ◽  
Vol 10 (03) ◽  
pp. 245-256 ◽  
Author(s):  
E.G. Woods
Keyword(s):  
Flow Rate ◽  
Single Layer ◽  
Pressure Response ◽  
Test Results ◽  
Well Test ◽  
Reservoir Model ◽  
Reservoir Properties ◽  
Pulse Test ◽  
Pulse Testing ◽  
Single Well

Woods, E.G., Member AIME, Esso Production Research Co., Houston, Tex. Abstract A mathematical investigation of pressure response of two-zone reservoirs indicates apparent transmissibility (kh/ ) obtained by pulse testing is always equal to or greater than the total transmissibility of the zones, and that apparent storage (phi ch) is always equal to or less than the total storage of the zones. These apparent zone properties approach total properties as vertical fluid communication between zones increases. The presence of non uniform wellbore damage in the zones alters the division of flow between zones, and consequently, alters their apparent transmissibility ratio. In the absence of wellbore damage. the flow-rate ratio is a good estimator of the transmissibility ratio of the zones. A procedure is proposed for advantageously using differences in reservoir properties determined by single-well tests and pulse tests to describe flow properties of two-zone reservoirs. A numerical properties of two-zone reservoirs. A numerical example is included. Introduction Pulse tests, interference tests, and single-well pressure buildup or drawdown tests have been used pressure buildup or drawdown tests have been used to estimate reservoir properties. These pressure transient tests are normally analyzed with mathematical models which assume that the reservoir is a homogeneous single layer. Various techniques for analyzing single-well test data to obtain information about the properties of layered reservoirs have been shown by others to have limited applicability. This mathematical study was undertaken to determine what errors could be caused by interpreting pulse tests (in a multizone reservoir) with a single-layer model. Pulse testing is based on the measurement and interpretation of a pressure response in one well to a transient pressure disturbance introduced by varying flow rate at an adjacent well. The measured pressure response is usually a few hundredths of a pressure response is usually a few hundredths of a pound per square inch. Pulse-test terminology is pound per square inch. Pulse-test terminology is shown in Fig. 1; Johnson et al. give a complete description of pulse testing. Measured at the wellhead or in the wellbore, pressure response is a function of reservoir pressure response is a function of reservoir transmissibility (T=kh/mu) and diffusivity (n = k/phi cmu) in the region between the two wells; from these two quantities reservoir storage ( = /n=phi ch) can be derived. The analysis presented here discusses additional reservoir information made available by pulse testing and shows that single-well test and pulse-test results can be combined to give more information about a two-zone reservoir than either type of test alone. Also, procedures are given for estimating the magnitude of error if test results of a two-one reservoir are interpreted with the assumption that it is a one-zone, vertically homogeneous, reservoir. Discussions of theoretical work, field data requirements, interpretation procedure, and a numerical example follow. Details of the mathematical model are given in the Appendix. THEORETICAL STUDY - TWO-ZONE MODEL Reservoir Model - Assumptions and Boundary Conditions A reservoir model consisting of two zones penetrated by two wells, each of which is completed in both zones was assumed (Fig. 2). SPEJ p. 245

scholarly journals Home Care in Germany: Philosophy of Treatment, Results of Intensive Care

1977 ◽  
Author(s):  
H.H. Brackmann ◽  
P. Hoffmann ◽  
F. Etzel ◽  
Eqli H. Hildenbrand
Keyword(s):  
Hemophilia A ◽  
Time Lag ◽  
Test Results ◽  
Treatment Results ◽  
Pathophysiological Process ◽  
General Test ◽  
New Ideas ◽  
General Goal ◽  
The University ◽  
And Training

In the FRG the work of several centers is concerned with introducing a program of self-treatment for hemophi1iacso The general goal of a self-treatment-program is: avoidance of a time lag due to long distances and the expansion of personal freedom and life style possibilities.In respect to the dosage and treatment duration various opinions exist, some of them differing quite noticably from ours. Our conception about the therapy, existing since the beginning of our program (June 1971), is based on an intensive cooperation with the department of orthopedics at the university. Through our teamwork the following results were achieved:- the evaluation of 17.196 acute bleedings registered 93% joint and muscle bleedings- 98% of the patients over 11 years of age with severe and semi-severe hemophilia A or B revealed at least one, in several cases more, arthropathic changes- the pathophysiological process of a joint bleeding leads to an important electromyographic test as well as to new ideas about biomechanic.Based on the general test results a specific dosage plan for each patient resulted, which, together with the orthopedic findings took into consideration the attained biological recovery. Since our goal is the strenghtening and training of muscle in general, every patient receives a specially adopted training program, which largely excludes bleeding. Our results have lead to a 90% improvement of the original orthopedic finding.

scholarly journals Potential preanalytical and analytical vulnerabilities in the laboratory diagnosis of coronavirus disease 2019 (COVID-19)

2020 ◽  
Vol 58 (7) ◽  
pp. 1070-1076 ◽  
Author(s):  
Giuseppe Lippi ◽  
Ana-Maria Simundic ◽  
Mario Plebani
Keyword(s):  
Diagnostic Accuracy ◽  
Diagnostic Errors ◽  
Laboratory Diagnosis ◽  
Test Results ◽  
Rt Pcr ◽  
Viral Recombination ◽  
Technical Issues ◽  
Diagnostic Window ◽  
Novel Coronavirus ◽  
And Storage

AbstractA novel zoonotic coronavirus outbreak is spreading all over the world. This pandemic disease has now been defined as novel coronavirus disease 2019 (COVID-19), and is sustained by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). As the current gold standard for the etiological diagnosis of SARS-CoV-2 infection is (real time) reverse transcription polymerase chain reaction (rRT-PCR) on respiratory tract specimens, the diagnostic accuracy of this technique shall be considered a foremost prerequisite. Overall, potential RT-PCR vulnerabilities include general preanalytical issues such as identification problems, inadequate procedures for collection, handling, transport and storage of the swabs, collection of inappropriate or inadequate material (for quality or volume), presence of interfering substances, manual errors, as well as specific aspects such as sample contamination and testing patients receiving antiretroviral therapy. Some analytical problems may also contribute to jeopardize the diagnostic accuracy, including testing outside the diagnostic window, active viral recombination, use of inadequately validated assays, insufficient harmonization, instrument malfunctioning, along with other specific technical issues. Some practical indications can hence be identified for minimizing the risk of diagnostic errors, encompassing the improvement of diagnostic accuracy by combining clinical evidence with results of chest computed tomography (CT) and RT-PCR, interpretation of RT-PCR results according to epidemiologic, clinical and radiological factors, recollection and testing of upper (or lower) respiratory specimens in patients with negative RT-PCR test results and high suspicion or probability of infection, dissemination of clear instructions for specimen (especially swab) collection, management and storage, together with refinement of molecular target(s) and thorough compliance with analytical procedures, including quality assurance.

A Multicenter Evaluation of a Nongel Mechanical Separator Plasma Blood Collection Tube for Testing of Selected Therapeutic Drugs

2020 ◽  
Vol 5 (4) ◽  
pp. 671-685
Author(s):  
Svetlana Morosyuk ◽  
Julie Berube ◽  
Robert Christenson ◽  
Alan H B Wu ◽  
Denise Uettwiller-Geiger ◽  
...  
Keyword(s):  
The Other ◽  
Initial Time ◽  
Therapeutic Drug ◽  
Blood Collection ◽  
Test Results ◽  
Sample Storage ◽  
Therapeutic Drugs ◽  
Collection Tube ◽  
And Storage ◽  
Blood Collection Tube

Abstract Background Some therapeutic drugs are unstable during sample storage in gel tubes. BD Vacutainer® Barricor™ Plasma Blood Collection Tube with nongel separator was compared with plasma gel tubes, BD Vacutainer PST™, PST II, and BD Vacutainer Serum Tube for acetaminophen, salicylate, digoxin, carbamazepine, phenytoin, valproic acid, and vancomycin during sample storage for up to 7 days. Methods Seven hospital sites enrolled 705 participants who were taking at least one selected drug. The study tubes were collected and tested at initial time (0 h), after 48 h of storage at room temperature and on day 7 (after additional 5 days of refrigerated storage). The performance of BD Barricor tube was evaluated for each drug by comparing BD Barricor samples with samples from the other tubes at 0 h from the same participant; stability was evaluated by comparing test results from the same tube at 0 h, 48 h, and 7 days. Results At 0 h, BD Barricor showed clinically equivalent results for selected therapeutic drugs compared with the other tubes, except phenytoin in BD PST. Phenytoin samples ≥20 µg/mL in BD PST had 10–12% lower values than samples in BD Barricor. During sample storage, all selected drugs remained stable for 7 days in BD Barricor and in serum aliquots. In BD PST, all drugs remained stable except phenytoin and carbamazepine and in BD PST II except for phenytoin. Conclusion The BD Barricor Tube is effective for the collection and storage of plasma blood samples for therapeutic drug monitoring without sample aliquoting.

Application of Leakage Rates Measured on Scaled Cask or Component Models to the Package Containment Safety Assessment

2018 ◽  
Author(s):  
Annette Rolle ◽  
Viktor Ballheimer ◽  
Tino Neumeyer ◽  
Frank Wille
Keyword(s):  
Test Results ◽  
Spent Fuel ◽  
Thermal Tests ◽  
Containment System ◽  
Leak Tightness ◽  
Accident Conditions ◽  
High Level ◽  
Elastomeric Seals ◽  
Component Models ◽  
And Storage

The containment systems of transport and storage casks for spent fuel and high level radioactive waste usually include bolted lids with metallic or elastomeric seals. The mechanical and thermal loadings associated with the routine, normal and accident conditions of transport can have a significant effect on the leak tightness of such containment system. Scaled cask models are often used for providing the required mechanical and thermal tests series. Leak tests have been conducted on those models. It is also common practice to use scaled component tests to investigate the influence of deformations or displacements of the lids and the seals on the standard leakage rate as well as to study the temperature and time depending alteration of the seals. In this paper questions of the transferability of scaled test results to the full size design of the containment system will be discussed.

Pulse-Testing Response for Unequal Pulse and Shut-In Periods (includes associated papers 14253, 19365, 20792, 21608, 23476 and 23840 )

1975 ◽  
Vol 15 (05) ◽  
pp. 399-410 ◽  
Author(s):  
M. Kamal ◽  
W.E. Brigham
Keyword(s):  
Pressure Gauge ◽  
Cycle Period ◽  
Time Lags ◽  
Pulse Test ◽  
Flow Disturbances ◽  
Pulse Ratio ◽  
Pulse Testing ◽  
Highly Sensitive ◽  
Dimensionless Groups ◽  
Interference Tests

Abstract A theoretical study was carried out to developthe general equations relating-time lags and responseamplitudes to the length of the pulse cycles andthe pulse ratios of these cycles for pulse testswith unequal pulse and shut-in times. Thesevariables were related to the reservoir parameters using appropriate dimensionless groups. Theequations were developed by using the unsteady-stateflow model of the line source for an infinite, homogeneous reservoir that contains a single-phase, slightly compressible fluid. A computer programwas written to calculate the values of The three corresponding time lags and the response amplitudesat given dimensionless cycle periods and pulseratios using these general equations. For different values of the pulse ratio rangingfrom a 0.1 to 0.9, the time lags and responseamplitudes were calculated for dimensionless cycleperiods ranging from 0.44 to 7.04. This range ofcycle period and pulse ratio covers all practicalranges over which pulse testing can be usedeffectively. Curves relating the dimensionless timelag to the dimensionless cycle period and thedimensionless response amplitude were constructed JOT each case. It was also found that both thedimensionless cycle period and the dimensionlessresponse amplitude can be represented as simple exponential junctions of the dimensionless timelag. The coefficients of these relations are functionsonly of the pulse ratio. Introduction Two wells are used to run a pulse test.These two wells are termed the pulsing well and theresponding well. A series of flow disturbances isgenerated at the pulsing well and the pressureresponse is recorded at the responding well.Usually, alternate periods of flow and shut in (or injection and shut in) are used to generate the flowdisturbances at the pulsing well. The pressureresponse is recorded using a highly sensitive differential pressure gauge. Pulse testing has received considerable attentionbecause of be advantages A has over theconventional interference tests. The pressureresponse from a pulse test can be easily detectedfrom unknown trends in reservoir pressure. Pulsetest values are more sensitive to between-wellformation properties; thus, a detailed reservoirdescription can be obtained from pulse testing. In all the work that has been reported on pulsetesting, it was assumed that the flow disturbancesat the pulsing well were generated by alternate periods of flow and shut in or injection and shut in.The pulsing period and shut-in period were alwaysequal. There bas been no study of pulse testing with unequal pulse and shut-in periods. Such a studymight have indicated whether other pulse ratioswill produce higher response amplitudes than theequal-period tests. The main purpose of this studyis to determine the response of pulse testing tounequal pulse and shut-in periods and to find theoptimum pulse ratio that gives the maximum responseamplitude. PULSE-TEST TERMINOLOGY Fig. 1 shows the pulse-test terminology as usedin this paper. SPEJ P. 399^

Overdamped slug test in monitoring wells: review of interpretation methods with mathematical, physical, and numerical analysis of storativity influence

1998 ◽  
Vol 35 (5) ◽  
pp. 697-719 ◽  
Author(s):  
Robert P Chapuis
Keyword(s):  
Numerical Analysis ◽  
Classical Solution ◽  
Heat Conduction Problem ◽  
Solid Matrix ◽  
Test Results ◽  
Slug Test ◽  
Slug Tests ◽  
Monitoring Wells ◽  
Pulse Test ◽  
Negligible Influence

Several methods are available to interpret slug tests; however, when applied to the same test data, they usually yield very different results. The methods are classified into three categories depending on their assumptions about the solid matrix deformability during the test. This paper deals with overdamped tests for elastic solids that deform instantaneously. It provides a unified interpretation of transmissivity T and storativity S based on the velocity graph for variable-head tests in monitoring wells or cased boreholes. If S has little influence, the velocity graph is a straight line. If S has some influence, the graph should give a smooth curve. However, smooth curves are exceptions in practice, thereby leading to a reexamination of the influence of S during a slug test. Three independent approaches are used. (1) A mathematical review shows that the overdamped solution, as adapted from a heat conduction problem, did not correctly treat storativity terms and the type of problem: it corresponds to a special pulse test, not a slug test. (2) A physical investigation of deformability shows that the influence of S does not exceed 1% of the initial slug for most compressible materials. Thus, it is almost impossible to detect its influence in test results. (3) Numerical analyses confirm that S has a negligible influence: test results provide straight lines, not curves. The numerical analysis of the special pulse test provides exactly the classical solution, and the correct values of T and S after eliminating the confusion about storativity terms. It is concluded that (1) S has a negligible influence in slug tests, (2) the existing classical solution giving T and S must be abandoned, and (3) the velocity-graph equation and its integral equation (Hvorslev or Bouwer and Rice) which correctly describe the process must be used.Key words: slug test, hydraulic conductivity, storativity, numerical modeling.

Fiber optic time break

Geophysics ◽  
1996 ◽  
Vol 61 (1) ◽  
pp. 294-298 ◽  
Author(s):  
Anton W. Kepic ◽  
R. D. Russell
Keyword(s):  
Time Lag ◽  
Geophysical Methods ◽  
Personal Communication ◽  
Electrical Current ◽  
Explosive Material ◽  
Actual Performance ◽  
The Cost ◽  
Explosive Devices ◽  
And Storage ◽  
Better Than

Geophysical methods that use explosive seismic sources need to produce an accurate time break signal at the time of the blast. This is generally achieved with a seismic detonator, a special variety of electrical detonator (or cap) that is designed to have minimal latency between the injection of electrical current into the detonator and initiation of the explosion, as well as having a slightly higher base charge and better water resistance. A time‐break signal is obtained by either electronically controlling or monitoring the blast current. Seismic detonators are guaranteed to have better than a millisecond latency if sufficient current is injected into the leads; the necessary current is usually 5 to 10 amps. A millisecond tolerance is acceptable for most seismic work but may not be sufficient for shallow studies or for crosswell tomography. However, in fairness to the seismic detonator, the actual performance is generally better: Burrows (1936) and, independently, Rolland and White (1937) reported a time lag of less than 0.3 ms with a deviation of 0.1 ms. These values have changed little since the 1940s. The MK 2 from C.I.L. Inc. (a division of I.C.I.) has an average lag of 0.3–0.4 ms (personal communication with I.C.I. explosives). Major improvements in electric detonator design have been in the areas of safety and durability. A much greater disadvantage for explosive sources are the strict regulations on the transport and storage of explosive devices (Tour, 1992). The cost of complying with these regulations may prohibit the use of explosives in small surveys or in remote areas. An example is the transport of explosives by aircraft: the only passengers allowed on board are those neccesary for completing the flight and for transporting the explosives. Chartering an aircraft to transport a small amount of explosive material is too costly for many geotechnical and mining geophysics surveys.

scholarly journals Phasic action of the tensor muscle modulates the calling song in cicadas

1996 ◽  
Vol 199 (7) ◽  
pp. 1535-1544
Author(s):  
P Fonseca ◽  
R Hennig
Keyword(s):  
Electrical Stimulation ◽  
Sound Production ◽  
Time Window ◽  
Time Lag ◽  
Motor Units ◽  
Pulse Amplitude ◽  
Time Correlation ◽  
Calling Song ◽  
Sound Pulse ◽  
Stimulation Of

The effect of tensor muscle contraction on sound production by the tymbal was investigated in three species of cicadas (Tettigetta josei, Tettigetta argentata and Tympanistalna gastrica). All species showed a strict time correlation between the activity of the tymbal motoneurone and the discharge of motor units in the tensor nerve during the calling song. Lesion of the tensor nerve abolished the amplitude modulation of the calling song, but this modulation was restored by electrical stimulation of the tensor nerve or by mechanically pushing the tensor sclerite. Electrical stimulation of the tensor nerve at frequencies higher than 30­40 Hz changed the sound amplitude. In Tett. josei and Tett. argentata there was a gradual increase in sound amplitude with increasing frequency of tensor nerve stimulation, while in Tymp. gastrica there was a sudden reduction in sound amplitude at stimulation frequencies higher than 30 Hz. This contrasting effect in Tymp. gastrica was due to a bistable tymbal frame. Changes in sound pulse amplitude were positively correlated with changes in the time lag measured from tymbal motoneurone stimulation to the sound pulse. The tensor muscle acted phasically because electrical stimulation of the tensor nerve during a time window (0­10 ms) before electrical stimulation of the tymbal motoneurone was most effective in eliciting amplitude modulations. In all species, the tensor muscle action visibly changed the shape of the tymbal. Despite the opposite effects of the tensor muscle on sound pulse amplitude observed between Tettigetta and Tympanistalna species, the tensor muscle of both acts by modulating the shape of the tymbal, which changes the force required for the tymbal muscle to buckle the tymbal.

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