Personal 3D audio arrives
A new technology from Ireland allows you to experience full surround sound without anybody else knowing about it. Paul Skelton reports.
Headphone technology has unquestionably improved dramatically over the years, to the point where a company like beyerdynamic can release the excellent DT 1990 PRO and listeners can be content with their purchase.
But, headphones are still headphones; they pale in comparison to the enveloping sound of a robust 7.1 surround sound system.
To rectify this, Irish audio research and development company Smyth Research has developed a technology that effectively transports the surround sound experience into the headphone environment, and the result is users’ inability to tell the difference between the two.
Called the Realiser, the technology recreates the virtual acoustics and loudspeakers of cinemas and studios in normal stereo headphones.
“Our goal with the Realiser technology is for users to not be able to tell the difference between wearing headphones and not,” Smyth Research representative Lorr Kramer says.
“The Realiser is based on principles that have been known for a long time but weren’t easy to implement. So that really is the cleverness of the design; it achieves something that as far as I know, nobody else does.
“The Realiser replicates very precisely the sound of real speakers in real rooms in headphones. You could call it ‘surround sound for headphones’.”
The Realiser technology was developed by Steve Smyth, who is perhaps best known for being involved in the creation of data compression algorithms that are used by DTS – the aptX 100 and Coherent Acoustics codecs.
“The Realiser is the result of a restless mind,” Lorr says.
“After leaving DTS, Steve started to look at communications between groups of people at opposite ends of a phone line (think teleconferencing). If there’s no picture, it can be quite difficult to discern who might be speaking at any given moment, especially if you don’t know the people. So Steve was looking at ways to ‘virtualise’ the environment so you could have directional cues.”
The purpose of the Realiser is to create in headphones the exact experience of sitting in a room with loudspeakers, Lorr says. A very specific room with specific loudspeakers, that is.
“For example, a home user might want to have a virtual encoding of somebody else’s ultra high-end home theatre system that they can’t afford. Alternatively, they might want to listen to audio in bed and not disturb anyone else while not being limited by the performance capabilities of stereo headphones.”
The Realiser 8 is an eight channel model that will virtualise up to eight speaker locations (i.e. 7.1). In 2017, the company will be releasing 16 and 32 channel models to keep up with new cinema formats like Dolby Atmos or Auro3D, which rely on additional height speakers.
Lorr explains that the 32 channel model is particularly suitable for the professional sound engineer.
“By virtualising sound stages, mixing engineers can work on a stage some of the time but then at a work station for the rest of the time, freeing up valuable studio space.”
So, how does it work?
The Realiser technology is based on the concept of Head Related Transfer Function (HRTF).
“That’s a fancy name for a fairly simple concept. We have two ears and, intuitively, we can tell left and right directionality (something to the left is going to be a little louder in the left ear and the sound is going to reach the left ear a little bit sooner than the right ear),” Lorr says.
“That’s quite easy to achieve in headphones, but in the real world we can also easily tell front from back and up from down. That’s harder to achieve with headphones because we don’t have ears on those axes.”
Sound is also affected by the shape of your body and head, in particular your outer ear – or ‘pinna’.
“So does your ear canal. You can actually graph the altered sound wave by putting a microphone in your ear. It looks like a complex filter and is quite jagged. Your brain filters the sound and then hears it as a direction. That’s how you tell top from bottom and front from back.
“Therefore, it stood to reason that we could recreate that effect in headphones in as much as in the real world you only have two ears. If we send the right signal into your two ears we should be able to recreate the strong and accurate sense of front and back and up and down, and any point in between.”
The way you do that is by applying through your headphones the same jagged shaping that your head and ears create.
“Everybody’s head shape is different, and because pinnas differ widely from one person to the next, somebody else measurements can be somewhat confusing. Simple surround sound processors that you can get in home theatre receivers average measurements out, so you get some sense of surround sounds but in order to get the level of accuracy that we do, you have to use your individual HRTF.
“To find this, we place microphones in your ears and measure your HRTF in the room that you wish to capture (e.g. sound stage, home cinema, etc). You sit in your favourite seat, put microphones in your ears and run some measurements to gather impulse responses, speaker response and room acoustics – it’s all entangled to form your personal HRTF.
“The Realiser box is then able to give you accurate playback that is essentially indistinguishable from the real thing.”
Another important aspect of how the Realiser technology works is head tracking, Lorr explains.
“We track your head position by means of a little sensor that is clipped on to the headphone band. During the measurement process, that sensor measures your head in a variety of positions.
“By knowing where your head is we can interpolate an HRTF for any position and we can rotate the image as necessary. So as far as your brain is concerned, the image isn’t moving at all.”
You can also use any headphones you like as the Realiser box will do a headphone measurement and take into account the little environment in the ear cup.
“Of course we strongly encourage you use good headphones. As everybody knows, you can’t install crummy speakers, put an equaliser on them and all of a sudden they’re wonderful. The same goes for headphones,” he says.
For now, Australians and New Zealanders have to buy direct from the company, which will ship from Northern Ireland.
The new Realiser 16, which becomes available in 2017, will be available in two versions – one that looks like a headphone stand and one that can be rack-mounted.