Lightning Headphone Test (Open Loop Test)

open_loop_headphone_screenshotThis sequence tests a stereo headphone connected to a portable audio device such as a mobile phone or MP3 player. It is particularly useful for testing headphones with proprietary connectors such as the Lightning connector which otherwise can’t be tested in a conventional “closed loop” test configuration.

The test stimulus is created in SoundCheck, saved as a WAV file and loaded on to the portable device for playback. Both left and right earphones are measured simultaneously using a continuous log sweep from 20 Hz to 20 kHz. The sequence uses a short 1 kHz tone, pre-pended to the normal test stimulus to automatically trigger the test when playback of the test signal begins; it also serves as reference tone for any frequency shift calculations. Post-processing precisely synchronizes the stimulus and response waveforms, and then calculation of the measurement parameters proceeds as with any conventional headphone. In this case, analysis is performed using the Time Selective Response (TSR) algorithm which performs THD and fundamental frequency response analysis simultaneously in addition to producing an impulse response. The fundamentals are then post processed to derive the sensitivity of the left and right channels at 1 kHz.

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Listen Awarded Patent for SC Amp Amplifier

patentListen’s revolutionary audio test amplifier, SC Amp, has been awarded US Patent # 9,386,387. This patent covers Listen’s unique high accuracy single channel impedance measurement method, which used a unique feedback circuit to offer dual channel accuracy using just a single channel. This enables full electrical and audio tests to be carried out simultaneously and with high accuracy using just 2 channels.

Specifically designed for the audio test market, SC Amp also incorporates several other features unique to the needs of audio test and measurement, such as low distortion (THD <0.025%) and a low noise floor (>100dB). Fixed gain eliminates calibration errors as there is no gain knob to be accidentally knocked or tweaked when it is in use. It supports the application of a DC voltage offset to the AC signal for testing transducers under adverse conditions, and features overload/output protection to prevent damage in case of shorting or overload.

Many unnecessary features found in regular audio amplifiers have been eliminated to keep production line operation simple and error-proof. Although it is designed to integrate seamlessly with Listen’s SoundCheck audio test and measurement software, it will also work well with other brands of test system.

Listen president, Steve Temme commented, ‘We are thrilled that the innovative design of this product has been recognized with this patent, and we are confident that this method will be quickly recognized by the marketplace.’

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New Manufacturing Team

evan_and_nickListen has expanded its manufacturing team with the addition of Evan Driscoll (left in picture) as Production Supervisor.  Evan graduated from Wentworth Institute of Technology in 2015 with a B.S. In Electronics Engineering Technology, where he also received the President’s award. Evan is very familiar with manufacturing at Listen, having held several internships and temporary positions at Listen over the past 3 years.

Evan replaces Nick Alston (right in picture), who has been promoted to the position of Manufacturing Supervisor after 2 years in the Production Supervisor role. Together, Nick and Evan manage all of our manufacturing and hardware assembly, test, and QC, ensuring that products are build and delivered on-time to high manufacturing standards.

A visit to Reviewed.com

Headphone Test using SoundCheckAbout Reviewed.com

Reviewed.com, part of the USA Today network, carries out quantitative reviews on a wide range of products including appliances, headphones, cameras, televisions and more. Since the beginning, their reviews have been built on the principle of using standardized scientific testing procedures to examine the performance of products, and a proprietary scoring method to ensure a level playing field amongst all manufacturers. Recently, I met with senior scientist Julia MacDougall, and received a tour of the facility and some insight into their headphone test methods, as well as a demonstration of their recently upgraded SoundCheck system.

The large brick building in Central Square, Cambridge, is in a part of town renowned for its young start up culture and unconventional work environments, so it’s no surprise to see a ping pong table next to the large, glass-walled conference room. However, once you get beyond the main lobby it is a labyrinth of test labs, each designed for testing a specific product. A room dedicated to camera testing features various test pictures on the walls, as well as 3d models with many moving and rotating parts to evaluate the camera’s capture of movement. Another lab was filled with massive flat screen televisions that were being tested for display performance, color measurement, luminance, contrast and more. Perhaps the most impressive was the appliance lab, where staff get to do their laundry while they work (in the interests of testing the washers), as well as working their way through many loads of white towels and stain strips that are marked with red wine, chocolate, sweat and more to scientifically evaluate the performance of the washing machines. Dishwashers, dryers, microwaves and ovens are also tested here, and a dedicated temperature and humidity controlled room contains many refrigerators filled with ‘dummy food’, the temperature of which is continuously monitored. The floor above the test labs is where their testers retreat to write up product reviews for their website, away from the whirr of tumble driers, swishing of dishwashers and stepped sine waves from the audio test lab.

 

The Audio Test Lab

The area that interested me the most was the smallest test area – the audio lab. Headphones are small and the test equipment is also compact, so a large room is unnecessary. Reviewed.com has been using Listen’s SoundCheck software since they first started looking for an objective way to test audio products back in 2007. Back then SoundCheck was being used for measuring mobile phones – smartphones were in their infancy, the next ‘hot product’, and Reviewed.com was the first review website to measure sound quality of a wide range of phones.

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New SoundCheck Brochure – Chinese

Our new SoundCheck® brochure is now available in Chinese. This short 12 page brochure is a top-level overview of the SoundCheck audio test system and associated hardware.

download_pdf_icon Download Electronic Version

or complete the form below to request a hard copy.

New SoundCheck Brochure

Our new SoundCheck® brochure is now available. This short 12 page brochure is a top-level overview of the SoundCheck audio test system and associated hardware.

download_pdf_icon Download Electronic Version

 

or complete the form below to request a hard copy.

Al Flint Joins Listen, Inc.

Al_FlintAudio test and measurement specialist, Listen, Inc.  has strengthened its engineering team with the appointment of Al Flint as Engineering Manager.

Al has spent the majority of his professional career in the audio industry, designing award-winning products and managing product development teams. Al’s career began at Sony Professional Products, where his designs included mic preamps and equalizers for the MXP-3000 mixing console. He then spent many years at Lexicon, where his technical contributions can be found in several effects processors. When Lexicon entered the consumer marketplace with digital surround sound processors, Al not only made design contributions to these products, but also established the development team and helped round out the Lexicon product line with multi-channel amplifiers and DVD players. After their acquisition by Harman, Al led a highly skilled team that designed Mark Levinson products, including several critically acclaimed amplifiers. After spending four years in the solar industry, where he managed development of high-power inverters, Al is returning to his audio roots and passion, and is excited about leading the development of cutting-edge audio and electroacoustic test and measurement products at Listen, Inc.

Test Sequences

Test Sequences