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IEC-60268-7 Headphone Sequences

seq_IEC-60268-7_distortion_impedance_no borderIEC-60268-7: Sound System Equipment – Part 7: Headphones and Earphones is an international standard intended to characterize the performance of headphones and earphones. The standard itself is a lengthy document, 9 Sections and 3 Annexes covering 46 printed pages. These SoundCheck sequences focus on the electro-acoustic tests which are detailed in Section 8 “Characteristics to be specified and their method of measurement”.

Five separate sequences are provided, each designed to measure specific characteristics. This approach provides the user with the flexibility to measure all or some of the characteristics of their headphone.

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Advances in Impedance Measurement of Loudspeakers and Headphones

Impedance measurement is often the sole electrical measurement in a battery of QC tests on loudspeakers and headphones. Two test methods are commonly used, single channel and dual channel. Dual Channel measurement offers greater accuracy as both the voltage across the speaker (or headphone) and the reference resistor are measured to calculate the impedance. Single Channel measurement methods are more commonly used on the production line because they only require one channel of a stereo soundcard, which leaves the other free for simultaneous acoustic
tests. They are less accurate, however, due to the test methods making assumptions of constant voltage or constant current. In this paper we discuss a novel electrical circuit that offers similar impedance measurement accuracy compared to complex dual channel measurement methods but using just one channel. This is expected to become popular for high throughput production line measurements where only one channel is available as the second channel of the typical soundcard is being used for simultaneous acoustic tests.

Authors: Steve Temme and Tony Scott
Presented at the 135th AES Conference, New York 2013

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Measurement of Harmonic Distortion Audibility Using A Simplified Psychoacoustic Model – Updated

A perceptual method is proposed for measuring harmonic distortion audibility. This method is similar to the CLEAR (Cepstral Loudness Enhanced Algorithm for Rub & buzz) algorithm previously proposed by the authors as a means of detecting audible Rub & Buzz which is an extreme type of distortion[1,2]. Both methods are based on the Perceptual Evaluation of Audio Quality (PEAQ) standard[3]. In the present work, in order to estimate the audibility of regular harmonic distortion, additional psychoacoustic variables are added to the CLEAR algorithm. These variables are then combined using an artificial neural network approach to derive a metric that is indicative of the overall audible harmonic distortion. Experimental results on headphones are presented to justify the accuracy of the model.

Authors: Steve Temme, Pascal Brunet and Parastoo Qarabaqi
Presented at the 51st AES Conference, Helsinki, Finland, 2013

Full Paper

Measurement of Harmonic Distortion Audibility Using A Simplified Psychoacoustic Model

A perceptual method is proposed for measuring harmonic distortion audibility. This method is similar to the CLEAR (Cepstral Loudness Enhanced Algorithm for Rub & buzz) algorithm previously proposed by the authors as a means of detecting audible Rub & Buzz which is an extreme type of distortion[1,2]. Both methods are based on the Perceptual Evaluation of Audio Quality (PEAQ) standard[3]. In the present work, in order to estimate the audibility of regular harmonic distortion, additional psychoacoustic variables are added to the CLEAR algorithm. These variables are then combined using an artificial neural network approach to derive a metric that is indicative of the overall audible harmonic distortion. Experimental results on headphones are presented to justify the accuracy of the model.

Authors: Steve Temme, Pascal Brunet and Parastoo Qarabaqi
Presented at the 131th AES Convention, San Francisco, 2012

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Headphone Testing (part 2)

Author: Brian Fallon.  Reprinted from the April 2012 issue of Voice Coil.

In part 2 of this comprehensive feature on headphone testing, Brian Fallon explains how to test more complicated types of headphones including bluetooth headphones, usb headphones and noise cancelling headphones.
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Headphone Testing – a comprehensive overview

Author: Steve Temme and Brian Fallon

With the headphone market growing towards $10 billion worldwide, and products across the price spectrum from under a dollar up to thousands, there are many and diverse quality expectations and test requirements. Many audio engineers have moved across from the shrinking loudspeaker industry to the burgeoning headphone marketplace. Although many of the characteristics that make for a good in-room listening experience with a loudspeaker – good frequency response, low distortion, no Rub & Buzz or loose particles, etc. – also apply to headphones, and many of the same test principles apply, there are some significant differences and additional issues associated with headphone measurement that need to be taken into account. These include couplers and associated correction curves, acoustic seal, fixturing and additional tests such as L/R tracking. In this paper we outline the issues that are common to testing all types of headphones as well as those specific to particular types of headphones such as Bluetooth and USB headphone testing, noise-cancelling headphones, and Max SPL measurements to prevent hearing loss.

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Headphone Testing (part 1)

Author: Steve Temme. Reprinted from the December 2011 issue of Voice Coil.

In part 1 of this 2-part series, Steve Temme discusses the basics of headphone testing.
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Automated Perceptual Rub & Buzz Distortion Measurement

Author: Steve Temme.  Reprinted from the September 2011 issue of Voice Coil.

In this article, Steve Temme discusses Listen’s latest work on perceptual Rub & Buzz measurement.
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