Understanding How We Hear Heightens Audio Perception
5/26/2011 5:29 AM
by Lindsey Snyder
Last week I met with Audyssey co-founder and CTO, Chris Kyriakakis, and Robb Mason, vice president of marketing, and we discussed one of the company’s latest technologies, called “low-frequency containment.” Essentially, it’s a “do not disturb” mode for your home audio system.
| Audyssey CTO Chris Kyriakakis. [photo credit: Brian Morri]|
LFC is based on the idea that walls block high-frequency sound better than low-frequency tones. This, of course, is why we hear bass thumping through floorboards during high action scenes being played out in another room or apartment, as well as that ubiquitous stereo bumping we sometimes hear on the street when some flashy car owner wants to flex his subwoofer’s muscle.
So, in an attempt to make these low-frequency sounds less disruptive to neighbors and housemates, LFC monitors media content and applies an algorithmic filter to limit the way bass is emitted by a sound system. This “mask” contains artificial bass tones that actually occur at higher frequencies, so the sound doesn’t travel through the walls as easily. The result is “an impression of bass” using psychoacoustics, a field Kyriakakis has studied extensively as an audio signal processing researcher at USC.
LFC will be added to several new AVRs on the market, likely in the form of a remote control switch. Look for Audyssey’s partners Denon, Marantz, and Onkyo to make formal product announcements this year at CEDIA EXPO in Indianapolis.
But beyond product introductions, my chat with Audyssey got me thinking about how fascinating psychoacoustics is in general.
Psychoacoustics is the study of how humans perceive sounds, or specifically, the psychological and physiological responses we have to audio.
Famed neurologist and best-selling author Oliver Sacks has pioneered psychological studies of how human brains react to music and observed astounding results on the effect that music can have on the rate at which our brains grow. He has documented these findings in Musicophilia: Tales of Music and the Brain
. While what Audyssey does with LFC reminded me of Sacks’ groundbreaking research, it differs in that Audyssey has studied how to change the way our bodies understand sounds around us, to produce, in this case, a more neighborly listening experience.
So basically, if I can fool my neighbors’ minds and bodies into not recognizing the disruptive nature of my late night movie watching or dance party while simultaneously fooling myself into hearing bass from lower frequency sound tones, then we all live in peace and harmony, right? Well done Audyssey for solving one of society’s greatest residential conflicts.
| Audyssey's products, like this MultEQ calibration kit, are built with an understanding of how we hear.|
But even further, our discussion, got me wondering about where the ideas of psychoacoustics originated from, and while maybe not imperative knowledge for installing the latest home entertainment system, it does make for interesting dinner party fodder or material for your next industry networking event.
Kyriakakis informed me that much of the foundation for psychoacoustics comes from the Venetian composer and violinist Guiseppe Tartini. He is credited with discovering a psychoacoustic phenomenon known as a combination tone (also known as a sum tone or difference tone). When two tones are played at the same time, distortion effects in the ear produce another tone as a result. Adding in some basic arithmetic, Tartini had the basis for understanding human sound perception. He discovered this simply by experimenting with the strings on his violin.
“At Audyssey we think it makes sense to build technology and products with an understanding of how we hear,” Kyriakakis wrote on Audyssey’s blog.
If you're interested in learning more about how we hear and how those physiological reactions can influence the quality and impact of the technology we use, I encourage you to check out Audyssey’s blog
where Kyriakakis explains in great detail the type of research he and his colleagues have conducted at USC and how they use it to develop Audyssey’s technology.