Multi-Tone Distortion (MTD)

• Multi-tone broad-band stimulus (music-like)
• Acoustic „finger print“ testing of speakers and audio systems (max SPL & distortion)
• Fundamental, level and transfer function
• Multi-tone distortion (MD) includes all distortion (HD, IMD)
• Relative MD and Total MD Ratio for simple limit setting
• Robust towards room influence
• Compliant to IEC60268-21
• Dedicated to fast-end-of-line testing
• Ensures overall consistency of production

The Multi-Tone Distortion (MTD) task is an add-on to the QC end-of-line test system. Closely related to the MTON module with focus on R&D applications, the MTD is based on multi-tone test signals.

In contrast to pure sinusoidal sweep excitation (such as SPL Task), multi-tone stimuli do not only excite harmonic distortion (HD) but also intermodulation distortion (IMD). Therefore, multi-tone distortion provides a much more comprehensive distortion pattern than harmonics alone. Due to the sparse broad band excitation, it is not always possible to identify distinct root causes and symptoms in multi-tone distortion, but it provides a more realistic distortion finger print than pure HD and IMD tests since operation conditions are closer to the final application with music. Therefore, the MTD is highly valuable to verify audio quality and max SPL handling in quality control.

S68 – QC MTD Multitone Task

The tutorial shows an overview of the principle of multi-tone measurement and it introduces our sister modules for R&D applications (MTON module) and End-of-Line testing (MTD task). It shows practical demonstrations for typical measurements and that all distortions (HD, IMD, Rub&Buzz) are available by a single measurement.

• Multi-Tone Distortion
• Waveform and Spectrum

• Any (except Suspension Parts)

Test Hardware 

• Klippel Analyzer 3 (KA3) or 
• Production Analyzer (PA) or
• 3^rd party audio interface (sound card)

License Dongle (USB)

PC

Software 

• QC Standard Software 6.6 or above
• QC Stand-alone Software
• QC in R&D

Accessories

• Microphones
• Power Amplifier
  • KA3 Amplifier Card or
  • KA3 QC Card or
  • 3^rd party amplifier

Operation and/or object templates for this module are available when creating a new operation or object in dB-Lab. This provides application specific setups and standard conforms tests.
Please find details on templates in Application Note AN 1001.

• Woofer End-of Line Test
• Passive Speaker

• Active Speaker

• Bluetooth Speaker 
  • Smart Speaker 
• Efficient, Mobile Quality Assurance of Rental PA Speaker with Audio-over-IP Amplifiers
• Microspeaker EoL Testing
  • Microphone Testing
• USB Mulimedia Speaker 
  • Automobile Audio System
• 2.1 System
• Alternate test setup
• Power Amplifier
• Headphone Testing

AN16 Multi-Tone Distortion Measurement
AN46 Test Enclosure for QC
AN79b Efficient, Mobile Quality Assurance of PA Speaker

Other Modules of the QC System

• 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

Related Products

• 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-Tone Measurement (MTON)
  Module provides sound pressure level (SPL) based characteristics using a multi-tone stimulus

• 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

• KLIPPEL LIVE Web Seminar Series 1: IEC 60268-21

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