Multi-Tone Distortion (MTD)

• 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).

S68 – QC MTD Multitone Task

• Multi-Tone Distortion
• Waveform and Spectrum

• 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)

Software 

• 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)

Accessories

• Microphones
• Power Amplifier
  • KA3 QC Card or Amp Card (opt.) or
  • External, 3rd party Amplifier

• Driver test setup
• Passive system test setup
• Active 2.1 system with electrical and acoustical testing
• 5.1 system with electrical and acoustical testing
• Microphone test setup
• Alternate test setup
• Headphone testing

AN16 Multi-Tone Distortion Measurement
AN46 Test Enclosure for QC

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

Other Modules of the R&D and QC System

• 3D Distortion Measurements (DIS)
  Module performs a series of steady-state measurements by using a single- or two-tone excitation signal varied in frequency and voltage
• Multi-Ton Measurement (MTON)
  Module provides sound pressure level (SPL) based characteristics using a multi-tone stimulus
• Spectrum Analysis (SAN)
  A-weighted SPL and distortion with/without noise generator or user-defined stimulus for noise & vibration or audio system testing
• Sound Pressure Task (SPL)
  Measurement of frequency response, THD and Rub & Buzz
• Sound Pressure and Impedance Task (SPL-IMP)
  Combined acoustic and electric measurement dedicated to fast QC testing
• Tone Burst Measurements (TBM)
  Peak SPL measurements using tone burst signals
• Transfer Function Measurement (TRF)
  Measurement of transfer function and harmonic distortion

• Voishvillo, et. al. , “Graphing, Interpretation, and Comparison of Results of Loudspeaker Nonlinear Distortion Measurements,” J. Audio Eng. Society 52, No. 4 pp. 332-357 (Apr. 2004)
• W. Klippel: Physical and Perceptual Evaluation of Electric Guitar Loudspeakers

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