3D Sound

HRTFs

A few years ago, three-dimensional sound would have entailed talking about fancy reverb and phase modulation of an audio signal sent to two speakers to create an additional sense of ambience or depth. The evolution of technology and the industry has redefined 3D audio as the real time manipulation of audio streams coming from front and rear speakers. In addition to panning around the various speakers, 3D audio also includes the movement of sound around the listener. Sounds are no longer just in front and back, but also now closer, farther, to the side and above and below the listener.

To completely understand how this is accomplished will probably require a doctorate in physics, biology, and computer science. We can however understand the fundamental theory behind this theory of psychoacoustics. The first requirement is to believe that this is a real phenomenon and not one created by peer or marketing pressure. This part is pretty easy, try sitting in swiveling chair and turn on your TV. Spin around the chair with your eyes closed, and you will be able to tell where the sound is. So we have determined that your two ears can process directionality of the sound. This is by the most part done by the brain analyzing timing and phase differences between the sounds to each of the ears.

Sensaura in the game

In choosing the Yamaha YMF744, Hoontech has also chosen to support Sensaura's 3D audio technologies. As you probably already know, Sensaura is not an API, but rather an implementation of DirectSound3D. This means that programs written for DirectSound3D will be able to take advantage of Sensaura's unique technologies. The highlights of Sensaura's technologies include MacroFX and Multidrive technology.

Sensuara Control Panel

Multidrive extends the HRTF (head related transfer functions) to the rear speakers as well as the front; this provides for a more immersive sound field that Sensaura likes to call a sphere of sound around the listener. MacroFX allows for sounds to be imaged closer to the listener. The original DirectSound3D implementations only allowed for sounds to get within a meter of the listener, anything closer would still sound the same. One limitation of MacroFX is that it requires that your internal mixer volume levels be set to no more than 60% to provide the additional volume headroom needed.

In regard to 3D quality, it really just boils down to software support. It looks like the future of 3D sound will be a battle of standards between Aureal and DirectSound3D. This is just like the Glide and Direct3D conflicts we saw only a few years ago. My prediction would be a single standard comprising the best of both approaches.