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Multi-Tone Distortion (MTD)

Optional Modules for the KLIPPEL QC Framework

Features and Benefits

  • Multi-tone stimulus and spectrum
  • Multi-tone distortion summing harmonic and intermodulation distortion
  • Analysis of input current or sound pressure
  • Compliant to IEC60268-21
  • Dedicated to fast-end-of-line testing
  • „Fingerprint“ testing of speaker and sound systems
  • Diagnostics using multi-tone distortion
  • Ensures overall consistency of production
  • Optional noise floor check

The Multi-Tone Distortion Task (MTD) is an add-on to the QC end-of-line test system. This module can be inserted as a test step (task) in any existing QC test. It is based on multi-tone test signals. 
Multi-tone stimuli excite not only harmonics distortion (such as chirp signals used in SPL task) but also inter-modulation distortion that provide a much more comprehensive distortion pattern than harmonics alone. Due to the higher number of excited frequencies it is not possible to separate distinct causes and symptoms which as can be done for harmonics and IM distortion analysis. In fact, multi-tone distortion are used to identify a distortion fingerprint which is a meaningful quality measure of audio products since multi-tone stimuli are quite close to normal music signal properties.

A multi-tone test can be applied to acoustic (sound pressure) and electric (input current) signals using a microphone or a Klippel Analyzer hardware (PA, KA3). This allows a separation of symptoms caused by the electro-mechanic part of the audio product (current) or includes in addition also vibration and radiation effects (sound pressure).

Test Objects

  • Any (except Suspension Parts)


Test Hardware(capture and/or playback hardware)

  • PA, KA3 (acoustical and electrical testing)
  • Soundcard, Wireless, Bluetooth (acoustical testing only)

License Dongle (USB)


  • QC Standard version 6.6 or higher (MTD license required)
  • Not available for QC Basic
  • Available as module for R&D Software 210.816 or higher (MTD license required)



dB-Lab Operation Template: QC Multi-tone Distortion (MTD)

Related Information

Other Modules of the R&D and QC System

Literature and Papers


International Electrotechnical Commission
IEC 60268-21 Sound system equipment - Part 21: Acoustical (output-based) measurements