Tag Archive for: check your cables

Audio Measurement Troubleshooting: 10 Time-Saving Tips

Audio Measurement TroubleshootingAudio measurement troubleshooting can be challenging. All too often we plug and unplug things, tweak settings and re-test, often changing several variables at once. A consistent and logical approach greatly accelerates the process.  Here, we share the process that our experienced team of support engineers has developed to assist customers. Follow these 10 audio measurement troubleshooting tips to quickly get to the root of your problems.

  1. Check your cables. Cables are the single biggest cause of setup problems! Make sure all your cables are properly connected and in the right place. Next substitute alternate cables one at a time – cables often get broken inside or damaged, even though they pass visual inspection. Make sure you understand the different types of cables and when you should use each – particularly where they look similar, e.g. single-ended and balanced cables. It’s a good idea to label your cables to make it quick and easy for anyone to replicate your measurement setup and quickly fix things if anything becomes unplugged.
  2. Check everything is plugged in! It sounds obvious, but if there is no output signal or not what you expect (e.g. it just looks like noise), check that everything is plugged in and turned on – not just the computer, but all audio interfaces, amplifiers, hardware, microphone power supplies etc.
  3. Run a self-test. Always run a self-test before making measurements to confirm that your measurement system and cables are working correctly. This facility is usually built into your measurement system and confirms that all components are working as expected.
  4. Make one change at a time and document everything. Don’t move cables, tweak the sequence and change the microphone position all at once – you won’t know what the cause of the problem was! Change one thing at a time, and keep a checklist of what you have done (this will be useful if you need to call customer support).
  5. Check your audio interface configuration. If your audio interface is incorrectly configured, nothing else will work. Ensure sound monitoring is switched off to prevent feedback, and make sure you are using the full dynamic range. Try making a loopback (output to input) measurement on the audio interface using the appropriate SoundCheck self-test. It should have a flat frequency response.  If your frequency response looks noisy it is likely that you have insufficient gain. You should have unity (0dB) gain when looped back on itself and very low THD. Latency should be consistent and repeatable and must be ≥ 0 Record Delay. There are many places where audio interface settings can be incorrectly configured  – check your hardware setup, ASIO control panel and mixer (if applicable), device front panel (if applicable) and Windows audio device settings.
  6. Calibrate your signal paths. Calibrating your signal paths is critical to accurate measurements and you should always have a multimeter and an acoustic calibrator handy! Calibration should be carried out at regular intervals as well as when you first run the test, particularly if there is a change in atmospheric conditions. Good measurement microphones and electronics are typically very stable but loudspeakers e.g. mouth simulators are generally very non-linear and their performance changes with temperature. It’s  always a good idea to warm up a loudspeaker before testing it by playing pink noise for example at a reasonable level. Factories should re-calibrate every day or at the beginning of every shift.
  7. Measure twice. Always measure something at least twice on the first measurement to make sure that you get the same result. This helps identify problems with the setup or background noise. It’s far better to discover this on the first measurement than at the end of a day of data collection! A golden unit, e.g. a demo speaker that you have measured many times, is a good sanity-check if measurements appear unexpected. A golden unit is advantageous over calibration as it also takes into account the fixturing and test environment.
  8. Check your units and your resolution. Make sure you are measuring in your intended units. For example the difference between dB Pa and db SPL is 94dB. If you are not careful you could blow something up. It’s also important to check your resolution. Lower resolutions provide faster measurements, but it’s important to ensure that you are using enough. If you keep increasing the resolution until the curve doesn’t change, you can easily identify the lowest acceptable resolution to test at.
  9. When in doubt, look at your recorded time waveform. Use your software’s oscilloscope function to see if your recorded waveform looks noisy, has drop outs, or gets cut-off too soon.  Look at the peaks of the recorded waveform and Max FSD in the memory list to see if it looks unexpectedly flat – it may be overloaded and clipping. These problems are very difficult to see in the frequency domain.
  10. Minimize background noise. Background noise is the biggest cause of unrepeatable measurements, so minimizing this improves your test environment. Easy ways to minimize background noise impact include positioning the microphone closer to the source, increasing the test level, increasing the duration of the test signal, and using repeated averages of the test signal. Doubling the averages or signal duration should increase the signal to noise ratio by 3 dB.

We hope you found these audio measurement troubleshooting tips useful. Follow our blog for more handy hints for audio measurement.