Tag Archive for: perceptual distortion

End of Line Distortion Measurements

Steve Temme discusses the importance of detecting manufacturing-induced defects such as Rub & Buzz and Loose Particles during end-of-line testing, and explains the various algorithms that are used. He compares conventional and perceptual metrics for the measurement of Rub & Buzz, including Listen’s new enhanced Perceptual Rub & Buzz algorithm, and discusses why it can be beneficial to use both conventional and perceptual measurements in tandem.

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Enhanced Perceptual Rub & Buzz Demo Sequence

This sequence demonstrates how SC20’s new enhanced Perceptual Rub & Buzz algorithm compares to normalized Rub & Buzz and subjective listening. Running this sequence on a batch of good and bad buzzing loudspeakers should help identify by measurement, audibly defective units and where to set production limits. Starting the sequence, the user is asked at what test level to play a stepped sine sweep (Stweep™) in 1/12th octaves, from 20 kHz to 50 Hz. The user is encouraged to try different test levels and change sweep parameters to find the optimum settings to catch buzzing loudspeakers. The loudspeaker is measured via two channels of the audio interface. A calibrated reference microphone is connected to one of the channels and an impedance reference built into the SC Amp or AmpConnect is connected to the other. A HarmonicTrak™ Analysis step analyzes the recorded waveform from the reference microphone, and displays both the enhanced Perceptual Rub & Buzz and normalized Rub & Buzz graphs.

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The Evolution of Production Line Rub & Buzz Measurements

Steve Temme discusses the evolution of production line Rub & Buzz measurements in this April 2022 issue of AudioXpress. Starting with  simultaneous analysis of higher order harmonics, he explains the progression of improvements including the greater accuracy offered by normalized distortion measurements, and progressing to the introduction of perceptual metrics. He covers the introduction of the first perceptual distortion algorithm introduced in 2011, and the newest enhancements to this which offer the repeatability necessary for successful end-of-line perceptual distortion measurement, where the reduction in false rejects and resulting higher yields add significant value to speaker and headphone manufacturers.

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