All these factors provide information regarding the distance of the sound sources from your ears. HRTF (Head Related Transfer Function) is how sound interacts with your head and ears. Besides HRTF, the characteristics of sounds coming at you change as you move in your environment, as well as moving objects emitting sound change their distance from you (resulting in The Doppler Effect).
Sound in Your Head
Unlike hearing sound in the natural world or via speakers, when listening to audio (either music or movies) using wired headphones or headphones connected wirelessly to your TV, the sound seems to originate from within your head. Even sounds entering your ears from left or right in a headphone environment sound like they are on the left or right side of your head, instead of a distance from it. Various techniques deliver sound with a more natural depth that can closely approximate the characteristics of sound arriving at your ears as it might with your ears exposed to the natural environment. Even the use of open or closed headphones can impact the sonic signature.
Expanding the Headphone Sound Field
With stereo, expanding the sound field is a matter of placing center channel sound elements (such as vocals) in front of you, while the left and right channels are placed farther from the left and right of your head. The task is more complicated with surround sound, but it is possible to place left, center, right, left surround, right surround, or more channel (surround sound) cues accurately in the “space” beyond your head’s borders than inside it.
Surround Sound With Any Pair of Headphones
One way to access headphone surround sound is through a home theater receiver, AV preamp processor, or mobile device providing surround sound processing using one of the following formats:
Dolby Headphone: When combined with Dolby Pro Logic II processing on a home theater receiver, you can expand two-channel content to surround sound. Some headphones have Dolby Headphone processing built into them.DTS Headphone:X: Provides a horizontal surround environment and overhead sound cues with compatible content.Yamaha Silent Cinema: Can use any pair of headphones connected to any Yamaha Home Theater Receiver, HTIB (Home Theater-in-a-Box), or soundbar that provides Silent Cinema audio processing.Auro 3D Audio (for headphones): Provides an immersive sound environment with horizontal and overhead sound depending on the content.Dirac VR: For music, you can use any pair of headphones with a home theater receiver or mobile device that features Dirac headphone surround sound processing. Audio/Video VR applications require a compatible VR headgear system and content. Dirac VR processing includes head-tracking capability — if you turn your head, the sounds still come from the proper direction, just like listening to room speakers or natural sound.Smyth Research: Requires the purchase of a particular audio decoder/processor that provides inputs for sources, such as CD/DVD/Blu-ray Disc players and USB flash drives, and includes a similar head-tracking capability as the Dirac system.THX Spatial Audio: An immersive surround sound system available for various applications, emphasizing select gaming and AR/VR headsets.
Algorithms create a virtual surround environment that gives the listener an enveloping sound and removes it from within the listener’s head, and places the sound field in the front and side space around the head, which is more like listening to a traditional speaker-based surround sound system. All of the needed surround headphone audio processing for each method is in the home theater receiver, preamp, surround sound processor, or another compatible device. These technologies can work with wireless headphones (Bluetooth is limited to stereo). However, even if your home theater receiver or another device that provides headphone listening doesn’t come with built-in surround sound headphone processing, you can still access a surround sound listening environment with some headphones.
The Ultrasone S-Logic Headphone Surround System
Another type of approach to headphone surround sound is by German headphone maker Ultrasone. What makes the Ultrasone process different is the incorporation of S-Logic. The key to S-Logic is the position of the headphone speaker driver. The driver is not in the earpad center, where it would send sound directly to your ear, but slightly off-center. By placing the driver in an off-center position, the sound plays to the outer ear structure first, where it funnels into the middle and inner ear more naturally. The sound is as it would be in nature or when listening to speakers; the sound reaches the outer ear first and travels into the middle and inner ear. This approach can work very well. There is both an increased expansiveness and directional perception of the soundstage. Instead of the sound coming from left and right, the soundstage opens beyond the earpad borders. Sound appears to originate from slightly above and slightly behind the ears and somewhat from the front. With music, voice, and instrument, placement is exact and distinct. Although listening to DVD and Blu-ray surround soundtracks with the Ultrasone S-Logic system is not the same experience (rear sound effects are minimal) as listening to an actual 5.1 or 7.1 loudspeaker setup, it is still credible. One drawback is that the center channel is not quite forward enough; it is more in the center of and slightly above your head. The left, right, and surround effects have enough spaciousness and direction. Ultrasone has taken an innovative yet straightforward approach to headphone listening that’s suited for listening to music CDs or DVD/Blu-ray/Ultra HD Blu-ray soundtrack material. There is no additional equipment or special sound processing requirement other than the headphones. The effect is available with any amplifier or receiver with a headphone connection.
The Sennheiser and Sony Alternatives
Sennheiser and Sony provide another headphone option. Their systems combine wireless headphones with a unique headphone surround sound decoder/processor/amplifier. You can plug one or more source devices into the “processor,” transmit the audio signal wirelessly to the headphones, and listen to either stereo or virtual surround sound.
Personalized Holographic Sound From Creative Labs
Creative’s Super X-FI Headphone Holography requires installing an app that uses your phone’s camera to take pictures of your face and ears.
The app maps your head using the image information.After mapping, you need to connect a Super X-Fi headphone amplifier (or use a headphone from Creative with the amp built-in) and sign up for an account.The Super X-Fi app downloads the mapping information and headphone selection into the amp to provide the best possible listening experience. The sound appears to come from speakers set a distance away rather than from inside your head.You can experience Super X-Fi Holographic Sound from Android and iPhones, Macs and Windows PCs, the Sony PS4, and Nintendo Switch, with more to come.
Headphone Surround Sound For Gamers
In addition to the headphone surround sound solutions discussed so far, a different approach targets the console and PC gaming environments. This option uses headphones connected to an internal decoder/processor in the console or PC (may also require additional software) or an external decoder/processor placed in the connection path between the gaming console or PC and the gamer. The result is an intimate, immersive virtual (such as DTS Headphone:X or Dolby surround) listening experience that complements the visual gameplay.
The Bottom Line
There are several ways to access surround sound for a headphone listening environment.
Make use of virtual or digital sound processing technologies you can use with any pair of headphones. However, you need a home theater receiver or playback device (with a headphone connection) that has the desired surround sound processing built-in.Use special headphones that can create a surround sound listening environment with any amplifier or receiver with a headphone connection, regardless of whether the amplifier or receiver is equipped with dedicated virtual or DSP technology for surround sound headphone listening.Use a system that pairs wireless headphones with an external decoder/processor/amplifier.For gamers, use an option that combines specific headphones with additional decoding/processing techniques performed by your console/PC or a device that connects to your console/PC and the headphones.
All four approaches work. It boils down to what option best suits your listening needs.
