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External Synchronization (SYN)

Optional module of the KLIPPEL QC SYSTEM

Testing audio devices with unknown or varying delay (e.g. Bluetooth speaker) at high-speed requires synchronizing the data acquisition to the (unknown) moment of stimulus playback. The External Synchronization offers a flexible and easy to use solution integrated with standard QC measurement tasks. This fast synchronization technique compensates for delays (e.g. due to latency or processing) and triggers measurements with unique acoustical signals (watermark noise). Optionally, the stimulus itself may be used directly as the synchronization signal. This technique is robust against frequency range limitations, echoes and sample rate deviations. Stand-alone devices such as tablets require the stimulus to be transferred to the device and played back autonomously. QC provides the stimulus sound as a WAVE file and awaits the playback of the synchronization signal. Additionally, WAVE input provides the offline analysis of recorded responses (e.g. microphone testing).

  • Trigger tests with acoustical watermark
  • Sample accurate synchronization
  • Sample rate tolerance
  • Copes with asynchronous sources
  • Export and import wave files


USB Speaker

The stimulus is played back with a 3rd party audio device (USB audio device) with unknown delay. The synchronization is performed dynamically through the acoustical measurement channel. Subsequent measurements use the detected delay to trigger the analysis in the quasi-synchronous playback process. For test signal playback, the speaker audio device is directly used as output sound device for Klippel QC.

Bluetooth Speaker

This setup is similar to the USB speaker example above, but the test signals are transferred wireless via Bluetooth. 

Automobile Audio System

 If the device under test (in this example an automobile audio system) does not provide an accessible auxiliary signal input, the stimulus sequence must be transferred offline to the audio system. 

This requires fixed timing modes by using static delays between the measurements. The stimulus sequence is generated and exported by the QC system and copied to a suitable medium (e.g. CD or memory card). The QC system waits for the unique synchronization signal to trigger signal analysis at an arbitrary point of time. 

Handheld Recording Device

For measurements with handheld recording devices which

  • do not provide a signal output or
  • are used for mobile recordings distant from the analyzing syste

the measured response shall be analyzed offline. While recording, the microphone signal is stored on the devices storage. The resulting audio file is imported by the QC software for analysis.

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