3D-Audio and Radio Separation

Proven to provide a significant situational awareness and speech intelligibility enhancement through a more natural and intuitive auditory interface.


Spatially separated sound is what every person perceives, when not wearing a headset - so we should call it "natural sound". We actually do detect the direction of a natural sound and use the direction when relevant. Natural sound can be reproduced through a stereo headset when processing is applied to the sound.

The Terma solution is the only available end-to-end solution, which optimizes every aspect of spatial separation, and therefore provides the best performance available.   


Spatial separation of radios has proven to be a significant intelligibility improvement, as it provides a more natural and more intuitive auditory interface to the listener

Terma’s digital Aircraft Audio Management System (AAMS) offers a range of benefits which include:

  • Reduced workload
  • Improved situational awareness and survivability
  • Reduced hearing loss and fatigue
  • Improved speech intelligibility and flight safety.

For a detailed description of those benefits, refer to “Aircraft Audio Upgrades

3D-Audio is the Natural Sound
3D-Audio perception is a "baseline capability" of any human being (with a hearing ability). A 3D-Audio system basically recreates the "natural sound" (which by definition is 3D) in a standard stereo headset, so putting on the headset will in a matter of seconds enable the listener to perceive and understand it. The capability is utilized in two different ways with the Terma system. Radio separation simply positions each radio at a distinct direction, while 3D-Audio cueing in addtion delivers directional information in the most direct and intuitive way. 

3D-Audio Contains Embedded Directional Information
In addition to the "Radio Separation", an important advantage is the ability to present directions to the user by means of 3D-Audio. Since this is natural audio, one knows the feeling of hearing e.g. a door slam behind and instinctively and immediately knowing the position. If this was heard in a mono headset, one would not have a clue where the door was. So, to provide the same level of information in a mono headset, one would need to add a statement like "behind you" and such a statement takes time to speak and to understand. It should be obvious that hearing the actual door slamming is a lot faster to understand. So in the analogous situation, when a missile is launched, the response must appear within seconds, and the Terma audio system generates those extra seconds needed.

Identify and Focus on the most Important
In mono, the listener perceives each and every audio source as being played in the center of one's head. Multiple simultaneous sources are hard to separate. With 3D-Audio, each audio source is perceived as coming from a distinct direction (as in "real life"), and it is easier to separate them, choose which one to listen to/focus on, and simultaneously the direction could be used to indicate other properties of the audio (e.g. RADIO1 from one o’clock, RADIO2 from eleven o’clock, etc.).

Increased Number of Sources without loss of Integrity
With traditional mono, no more than 2 simultaneous audio cues/messages/tones can be understood by the listener (depending on the types of audio - i.e. voice/tone/alert). With 3D-Audio, more sources can be handled by the listener. Not in the sense that one can understand everything from each of the sources, but one can pick which sources to listen to and suppress the others.

3D-Audio Cuing
In order to reduce the pilot work load and situational awareness (SA), Terma is the first company in the world to have a 3D-Audio technology available and fielded to support these key enhancements. Initial studies on the utilization of the technology in a cockpit environment showed in a comparison test that the pilot would perceive the direction of an approaching missile threat 1.5 sec faster by using 3D-Audio cuing as compared to presenting the threat in a cockpit panel mounted display.

  • Obstruction warning and cueing head-up identification
  • Uses natural human capability of localizing sound sources in three-dimensional space
  • Instant attention on the threat, no need to understand voice message or interpreting the symbol on a 2D-display.


One-fit-all HRTF-based Solution
The Terma 3D-Audio solution is Head-Related Transfer Function (HRTF) based. The specific HRTF database used with the Terma system is a generic (one-fit-all) HRTF, developed and patented by Aalborg University. Individually adapted HRTFs (the transfer function measured for each individual user) is supported by the Terma system, but it has been verified that our generic HRTF provides excellent performance for airborne applications. A substantial logistics effort involved with individual HRTFs (measuring them for each user, and ensuring that the correct HRTF is installed and used on the aircraft) is avoided by the use of generic HRTF implementation.

3D-Audio with Headtracking
If the position of an audio source need to change relative to the listeners head (dynamic audio sources), it is necessary to switch between HRTF elements while playing the audio. Dynamic audio sources are required to present audio which must retain a position relative to the aircraft or other external coordinate system. The headtracker compensates for head movements to maintain the direction of the dynamic source. Integration with various head tracker systems, for this purpose, has already been performed. 

3D-Audio is the natural sound

3D-Audio application candidates
Examples of 3D-Audio cues are: 

  • Missile Warning System threats
  • Radar Warner Receiver threats
  • Laser Warner System threats
  • Threats from small arms detection systems
  • Indication of direction to beacon in Search & Rescue operations
  • Indication of terrain obstruction warning and cueing
  • Apply direction to audio cues to aircraft subsystems in order to link display and auditory information.