Friday, November 30, 2012

Behind Harman's Testing Lab

This past week I had an enjoyable time meeting well-known technology writer Robert Scoble who was visiting our Harman facilities in Northridge, CA along with his geek-in-command Sam Levine. As part of the tour, I showed  them our Reference Listening Room and Multichannel Listening Lab where we do product research and double-blind evaluations of loudspeakers. We discussed the science and philosophy behind how we design and measure the sound quality of our products.

One of the topics of discussion was my recent research that explores whether high school and college students from USA and Japan have different tastes and preferences in the quality of reproduced sound compared to older trained listeners.  We talked about differences in the tastes and performances of trained versus untrained listeners, and how Harman is able to accurately predict  subjective preference ratings of loudspeakers based on a predictive model that analyzes a set of comprehensive anechoic measurements.

After running Robert and Sam through a few trials of listener training using  our software "How to Listen", I decided to put them through a couple of double-blind listening test trials to see if they had the right stuff. They compared four different brands of floor-standing loudspeakers located  behind an acoustically transparent, visually opaque curtain where each loudspeaker is shuffled into the same position via an automated speaker shuffler. All of our tests are conducted double-blind because we have found that even trained listeners are influenced by nuisance variables such as brand, price, size, etc.

 In these tests Robert and Sam heard the same four loudspeakers that have been evaluated previously by hundreds of untrained listeners including young, old, American, Asian, and European listeners, whose preferences and performances were compared to those of our panel of trained listeners. From these tests, we have found evidence that most listeners prefer the most accurate, neutral loudspeaker regardless of age, culture or listening experience.

When the listening trials were done, the curtain went up, and Robert and Sam were surprised to discover their favorite choice was the most accurate loudspeaker which was the least expensive. The science works.  One of the speakers Robert didn't like was a model that he actually owned: it had excessive amounts of treble and upper bass, which I'm told is mandated by the manufacturer's marketing department who believe that "boom and tizz" are what their customers want. Luckily, I haven't met many of their customers, yet. Robert, then surprised me by turning on his camera doing an impromptu interview, which hopefully you'll enjoy. If you want to learn more about the engineering process and tools behind designing a speaker, check out the interview with one of our speaker engineering stars, Charles Sprinkle.

In my next blog posting I hope to discuss some of the exciting research we've been doing on the relationship between the perception and measurement of headphone sound quality. The goal is to develop the same science for measuring and predicting the sound quality of headphones that we've found useful for designing good sounding loudspeakers.  Stay tuned!