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Appendix

This tool is not a "measurement instrument"

This software is a simple signal analysis and observation tool using a PC and an audio interface. While it is useful for learning, hobbies, or initial estimations in development, it cannot be used for strict quality assurance or standards compliance testing.

☕ Coffee Break: Why is "Perfect Measurement" difficult?

You might think, "If I have a PC and an audio interface, I don't need a measurement instrument that costs millions, right?" However, there is a reason why dedicated instruments are expensive. It's because they have an "absolutely unwavering standard."

For example, an ordinary ruler expands and contracts slightly with temperature, but in professional settings, special rulers are used that guarantee "1 millimeter is absolutely 1 millimeter in any environment." This is the power of "calibration" and the value of dedicated measuring instruments.

MeasureLab is extremely excellent as a "handy and convenient ruler," but in situations where legal proof or absolute precision on the millimeter level is required, it must yield to professional rulers (dedicated measurement instruments). Even so, for everyday development and hobbies, this "convenient ruler" will surely be a powerful weapon for you!

Reliable Range and Reference-Only Range

What this tool excels at is observing "relative changes."

  • Reliable Use (Relative Use):

    • Relative Comparison: Confirming changes such as "whether the noise level decreased before and after a countermeasure" or "which of A and B has less distortion."
    • Operation Check: Visual confirmation of whether the signal is clipping, oscillating, or if the intended frequency is being output.
    • Troubleshooting: Identifying 50Hz/60Hz hum noise contamination or sudden glitches.

  • Reference Only:

    • Absolute Values (Voltage, Sound Pressure): Physical quantities other than dBFS (V, dBu, SPL) are merely estimated values unless corrected using a calibrated reference instrument.
    • Measurement in Minute Domains: Measurements of THD+N below -100dB or the noise floor are strongly affected by the performance limits of the PC and audio interface itself.

Troubleshooting

If you have trouble, please check the following items.

❓ No sound / No response to input

  • Power and Connection: Confirm that the audio interface is turned on and the USB cable is correctly plugged in.
  • Settings Widget: Confirm that the correct device (ASIO/WASAPI, etc.) is selected.
  • OS Shared Mode: Confirm that other recording software, browsers, or web conferencing tools are not occupying the device.

❓ Graph movement is jerky / Sound is intermittent

  • Buffer Size: Change Buffer Optimization to STABLE or ULTRA in the Settings widget.
  • CPU Load: Close other heavy applications.

❓ Screen appears to be frozen at startup

  • WISDOM Generation: On the first launch, it may take several tens of seconds to calculate "WISDOM (FFT optimization)." It is not a malfunction, so please wait.

❓ Mountain appears at a different frequency even though a 1kHz signal is being output

  • Sampling Rate Mismatch: Confirm that the sampling rate setting in MeasureLab and the setting on the audio interface side (or OS sound setting) are the same (e.g., 48kHz, 192kHz).

❓ I want to check detailed Error Logs (Command-Line Options)

If you encounter unexpected errors or need to provide debugging information, you can check the application logs. By default, logs are displayed in the "Logs" window within the application, but you can also output them to a file or change the log level using command-line arguments when launching the application:

  • --log-level: Set the logging level (DEBUG, INFO, WARNING, ERROR, CRITICAL). Default is INFO.
  • --log-file: Specify the path to save the log file. If not specified, logs are automatically saved to measurelab.log in the user data directory.

Example (macOS/Linux):

python main_gui.py --log-level DEBUG --log-file ./debug.log

Finally

If the problem is not resolved, please check the basic operation again with a loopback connection (direct connection from output to input) to see if there are any connection errors or cable defects.