Transitioning Audio Tests from R&D to the Production Line

Steve Temme discusses the transition from R&D to production testing in this March 2023 issue of AudioXpress. Production line audio testing poses many challenges such as noisy environments, harsh operating conditions, high throughput, relative limits, and more. In this article, Steve Temme shares his observations and outlines the main considerations to ensure a successful operation.

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Introduction to Production Line Audio Testing Article

Your product design is finalized, your prototypes are close to perfect, and your audio product is ready to move to production. But how do you ensure that the product hitting the retail shelves sounds exactly as you intended?
Your production line is probably thousands of miles away, with time zone and language complications. Pandemic-related restrictions make it hard to visit to configure, supervise, and train factory personnel. Furthermore, production is often outsourced to a contract manufacturer, adding another layer of complexity to both culture and information transfer.
Every production facility has one priority: to build products that meet the specifications with the greatest efficiency and highest yield possible for optimum profitability. Think about what that means for end-of-line tests. Their goal is to have as many units pass as possible. Tests must be fast to avoid slowing down the production line, and the test environment is generally noisy, often with variable temperature and humidity. The quest for high yields and manufacturing efficiency, along with challenging operating conditions and sometimes poor training, can result in unreliable measurements. When this happens, the only loser is you and your brand’s reputation.
I’ll never forget being told about a production line operator who increased pass-rate by opening the test box during measurements so that the factory background noise would mask the high-order harmonics to fool the perceptual Rub & Buzz algorithm. This might improve his yield, but it’s not so good when these products ship to customers! While this is one of the more outrageous violations of end-of-line test protocol, I have also seen many other questionable measurement practices over the years. In this article, I’ll try to de-mystify production tests and look at some simple measures that you can take to ensure a smooth transition.

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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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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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Soundcard-Based Production Line Loudspeaker Test

Author: Steve Temme
Reprinted from the July 2004 issue of Voice Coil
Steve Temme discusses high-end loudspeaker manufacturer, Peerless’s choice of SoundCheck® as their standard for testing their loudspeakers.

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Article Introduction

Soundcard-Based Production Line Loudspeaker Test
By Steve Temme, Listen Inc.

Quality and reliability are critical factors for success in the audio industry. In today’s global manufacturing environment, product testing is more important than ever, and products built in low-cost countries must be tested to the same standards as those manufactured in the US and Western Europe.

Peerless, one of the world’s leading manufacturers of high-end audio speakers, produces over half a million loudspeakers a year. Peerless belongs to the Danish Sound Technology group (DST), together with Vifa and Scan-Speak. Their headquarters in Karlslunde, Denmark, still produce a majority of the speakers, and the DST manufacturing facilities in China produce a growing number of speakers.

Every single speaker that Peerless manufactures is tested for acoustic quality using SoundCheck®, a soundcard-based electroacoustic test and measurement system. This offers significant advantages over conventional hardware-based systems including fast and simple production line use, low capital expenditure and easy analysis and sharing of test specifications and results (Photo 1).

Peerless has manufactured loudspeakers in Denmark since 1926, and in 1995 the former Vifa-Speak (now DST) established an additional manufacturing facility in Panyu, China. In 2002, Peerless established a second facility in Xiaolan, China. These modern facilities offer cost-effective, high quality manufacturing to supplement the output of the Danish factory.

Peerless conducts 100% quality testing of its products, and tests to exactly the same standards regardless of where the product is manufactured. In the Xiaolan facility, SoundCheck is also used for R&D work where a dedicated SoundCheck system measures frequency response and Thiele/Small parameters in a large 2pi room. With production lines several thousand miles apart, using the same test setup and equipment simplifies quality control (Photo 2). As Carsten Tinggard, the engineer responsible for the test systems, explains, “Our reputation is built on quality and reliability. Therefore, every loudspeaker that Peerless manufactures, either here in Karlslunde, or in China, is 100% tested as it comes off the production line using SoundCheck electroacoustic test software.”

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