Contemporary methods for realization and estimation of efficiency of 3Daudio technology application for sound interface improvement of an aircraft cabin

• Main Authors: O. N. Korsun, G. A. Lavrova
• Format: Article
• Language: Russian
• Published: MGTU im. N.È. Baumana 2014-01-01
• Series: Nauka i Obrazovanie
• Subjects: spatial audio-cues; 3D-audio technology; head related transfer function
• Online Access: http://technomag.edu.ru/jour/article/view/525

<p>High information load of crew is one of the main problems of modern piloted aircraft therefore researches on approving data representation form, especially in critical situations are a challenge. The article considers one of opportunities to improve the interface of a modern pilot's cabin i.e. to use a spatial sound (3D - audio technology). The 3D - audio is a technology, which recreates a spatially directed sound in earphones or via loudspeakers. Spatial audio-helps, which together with information on danger will specify also the direction from which it proceeds, can reduce time of response to an event and, therefore, increase situational safety of flight. It is supposed that helps will be provided through pilot's headset therefore technology realization via earphones is discussed.</p><p>Now the main hypothesis explaining the human ability to recognize the position of a sound source in space, asserts that the human estimates distortion of a sound signal spectrum at interaction with the head and an auricle depending on an arrangement of the sound source. For exact describing the signal spectrum variations there are such concepts as Head Related Impulse Response (HRIR) and Head Related Transfer Function (HRTF). HRIR is measured in humans or dummies. At present the most full-scale public HRIR library is CIPIC HRTF Database of CIPIC Interface Laboratory at UC Davis.</p><p>To have 3D audio effect, it is necessary to simulate a mono-signal conversion through the linear digital filters with anthropodependent pulse characteristics (HRIR) for the left and right ear, which correspond to the chosen direction. Results should be united in a stereo file and applied for reproduction to the earphones.</p><p>This scheme was realized in Matlab, and the received software was used for experiments to estimate the quantitative characteristics of technology. For processing and subsequent experiments the following sound signals were chosen: a fragment of the classical music piece "Polovetsky Dancings" from A.P. Borodin's opera "Prince Igor", the horn sounds, the modulated broadband noise (with the fixed position, and "wandering" in the range ±5º in the vertical direction with respect to the fixed position). In the course of experiments the examinee was offered to define in what of possible positions (on an azimuth ±80º, ±40º, 0º, on an eminence ±45º, 0º, and 90º - over the head) there is a virtual source of sound.</p><p>According to results of experiments, directions with "rough" gradation 90 ° (in a horizontal "at the left–direct-on the right", in a vertical ""up-direct-down") are distinguished with he high probability (on the average 0.94) for all types of signals. Thus the spectral content of signal is of no importance. Results of more accurate recognition with gradation of 40 … 45 ° depend on the type of signal and are different for horizontal and vertical channels. In the horizontal channel the probability of the correct recognition for broadband signals (the modulated noise, classical music) is 0,77 … 0,78, for a sound of horn it is 0,75. In the vertical channel for broadband signals (the modulated noise, classical music) the probability of the correct recognition is 0.48 … 0.50, for a sound of horn it is 0.36. The results allow us to assume that the person recognizes better the position of sound signal sources with rather wide spectrum close to the natural ones (broadband noise, symphonic orchestra).</p><p>Thus, as a result of the carried-out work the sound processing algorithms have been realized and the software to allow reproducing spatial audio-helps via earphones has been created. In the course of research the methods of a digital filtration as well the statistical methods to analyse the results of experiments have been used. The main result defining a scientific novelty of work is the objective quantitative characteristics of the 3D - audio technology, which are expedient for considering in designing the interfaces for pilots' cabins of modern aircrafts.</p>