FAQ

FAQ | Impedance

Q1: Which is the latest version of Impedance software?
Q2: Which are the current Impedance setup hardware elements?
Q3: What frontends are compatible with the Impedance software?
Q4: What probes are compatible with Impedance setup?
Q5: What is the size and weight of the total setup including the boxing?
Q6: What is the frequency limit of In-situ Absorption setup?
Q7: What should be the minimum sample size? 
Q8: What is the influence of reflections to the measurement?
Q9: What is the distance to measured material and frequency limitations?
Q10: Can the measurement be also performed under an angle?
Q11: Is it possible to excite the loudspeaker with different signals with the Impedance software? 
Q12: What is the minimal Signal to Noise Ratio to be able to obtain good results?
Q13: Are there limitations related to the material type? 
Q14: Can I use a wind protection on the probe while measuring?
Q15: What is the difference between the models and which one should I choose for my measurement?
Q16: What is the deviation range to be expected in the results?  
Q17: Can the results be affected by different amplification in the sound volume of the spherical loudspeaker?
Q18: How do I read the values for calibration?
Q19: Do I need to be the computer admin to run the software?
Q20: Why I don’t get any signal from the DAQ calibration procedure?
Q21: How can I activate my software?

Q1: Which is the latest version of Impedance software?  
Impedance 3.1


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Q2: Which are the current Impedance setup hardware elements?  
  • PI-probe
  • Signal conditioner
  • Scout 422
  • Double shielded PU cable
  • Impedance gun


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Q3: What frontends are compatible with the Impedance software? 
  • MFDAQ
  • Scout 422


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Q4: What probes are compatible with Impedance setup?   

PU-mini and PI-probe are usable with the Impedance setup. PI-probe is recommended for highly reflective samples.



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Q5: What is the size and weight of the total setup including the boxing?

Dimensions: 41 x 50 x 22 cm
Weight: 7 Kg



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Q6: What is the frequency limit of In-situ Absorption setup?  

The frequency range is in general 300-10kHz but the actual usable frequency range depends on the measured material type.



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Q7: What should be the minimum sample size? 

The sample should be at least 0.3 x 0.3m to have a good measurement of absorption and still a good term of comparison (at low frequency) with other methods (example, Kund’s tube). 



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Q8: What is the influence of reflections to the measurement?   

Reflected waves can introduce fluctuation in the spectrum. Different smoothing options are available in the software, recommendable in different scenarios:

  • If surrounding objects are far from the setup: Impulse response;
  • Multiple reflections with small amplitude compared to direct signal: Moving average smoothing;

This makes the setup more usable for in situ measurements. A situation with no reflection is more likely to give a better estimation of the absorption. 



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Q9: What is the distance to measured material and frequency limitations?

The measurement should be taken as close as possible to the surface.



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Q10: Can the measurement be also performed under an angle?
To perform measurements under an angle the probe should be rotated in the same angle for booth measurement steps: free field calibration and material test. Further investigation needs to be carried out in order to assess the maximum usable incidence angle.


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Q11: Is it possible to excite the loudspeaker with different signals with the Impedance software?  

It is possible to excite the sample with a white noise, sine sweep and pure tone, depending on the requirement of the measurement. Typically, sweep signal gives the best results as it concentrates all the energy in one band while exciting. 



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Q12: What is the minimal Signal to Noise Ratio to be able to obtain good results?

The system is developed to be used in situ so a certain noise level can be tolerated.Typically is recommended to have a Signal to Noise Ratio of 10 dBs, so that the results show good coherence. 



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Q13: Are there limitations related to the material type? 

The type of material used can determinate or reduce a little the usable frequency range of the setup in the low frequency and high frequency region but by definition any material can be used. It is recommended to use the PI probe as the package of the PU mini probe produces some deviations on the high frequency region.



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Q14: Can I use a wind protection on the probe while measuring?

Yes, as long as the wind-cap is used during the two measuring steps. The usage of a windcap will increase the distance probe-sample.



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Q15: What is the difference between the models and which one should I choose for my measurement?

The available models offer the following characteristics:

Model Plane wave Mirror source Q-term
Bandwidth - + +
Speed + + +/-
Robustness + + -
Accuracy - +/- +/-
Main disadvantage Low frequency errors. Negative absorption values are found because only plane sound waves inside the sample are considered.


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Q16: What is the deviation range to be expected in the results?



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Q17: Can the results be affected by different amplification in the sound volume of the spherical loudspeaker?

It is requested to maintain a constant amplification on the fed signal to the loudspeaker in the two measurement steps: the free field calibration and sample measurement stage.



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Q18: How do I read the values for calibration?

The response of the Microflown is not flat like a standard microphone, so next to a general sensitivity value it needs to be corrected via calibration. The calibration curve in amplitude and phase is defined by the coefficients inserted in the calibration report and needs to be inserted in the software. 



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Q19: Do I need to be the computer admin to run the software?

Yes, if not the program will not be able to run properly and can occur  “dtol.dll” error message or not loaded/ not found NIDAQ. For more information about these problems please read the manual section: ”Things to be taken into account” or contact Microflown Technologies Customer Suport.



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Q20: Why I don’t get any signal from the DAQ calibration procedure?

Either the button is not working or the DAQ is not recognized or is not selected the correct input.



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Q21: How can I activate my software?

To activate a license for every software you have to send an email with the two activation codes and the order number or the serial of the probe to



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