Audio system for a computer display

Abstract: A sound system for a computer display provides four loudspeakers 1 to 4 at the corners of a VDU screen. Under program control sound to the loudspeakers is mixed so as to simulate the emission of sound for positions or the screen corresponding to the positions of respective windows.

Description: The invention relates to an audio system for a computer display. In a personal computer there is usually a loud-speaker and audio circuitry for generating sounds in conjunction with programs as they are run. Speech or music may be simulated or played from a digital recording. A growing application for computers is in conferencing, where several users may be connected together in a network, each with a terminal. Each screen may contain representations of the users such as icons, photographic representations, or freeze-frame or even real-time video pictures. Each user will generally have a particular region of the screen devoted to him, with the program typically running under a windows environment. According to the invention there is provided visual display unit (VDU), the system comprising a plurality of loudspeakers distributed around the VDU, audio circuitry for driving the loudspeakers including means to allow a sound source signal to be variably distributed to the loudspeakers in amplitude and/or phase characterised in that the audio system is associated with a computer programmed to display an image relating to a sound source on a screen, wherein a particular region of the screen is devoted to the image, and wherein the screen co-ordinates of the image are processed to provide a control input to the audio circuitry whereby sound is generated which appears to emanate from a position having a predetermined relationship with the position of the image. It is found that there is enhancement of a user interface if the sound associated with a window appears to emanate from the position of the window. The invention provides a means of achieving this and in more general terms provides a means of generating sound which is spatially associated with the position of the image of the sound source on the screen. It will be seen that such a facility has application in various types of computer displays including games with moving sound sources and video type displays. There may be only three loudspeakers arranged in a triangle but preferably there are four at respective corners of the screen. Another arrangement is to provide a loudspeaker at the middle of each side of the screen. In use, the system would be provided in a computer programmed to display an image relating to a sound source, wherein the screen co-ordinates of the image are processed to provide a control input to the audio circuitry whereby sound is generated which appears to emanate from a position spatially co-ordinated with the position of the image. The image position and the apparent sound position may be aligned with respect to their distances from the centre of the screen. Alternatively it may be desirable to exaggerate the apparent position of the sound so that there is not spatial co-ordination, the position of the sound being further from the centre of the screen than the position of the corresponding image. Exaggeration may be required in one dimension only, for example the "up-down" dimension. The invention will further be described with reference to the accompanying drawing, of which the sole figure is a schematic diagram of an audio system in accordance with the invention. Referring to the drawing there is shown an essentially rectangular screen S of a VDU. Loudspeakers 1 to 4 are situated at the corners of the screen. The computer associated with the VDU is running a networked conferencing program which operates in a windows environment. Two windows A and B are shown at the top left and bottom right of the screen respectively. The system is able to distribute sound between the four loudspeakers to give the impression that sound is emanating from the screen at a position corresponding to the position of the appropriate window. For window A the sound will come predominantly from loudspeaker 1. If the window moves so will the apparent position of the sound source. Any number of windows can be present at once and the sound will be positioned independently for each window. So, for example, the sound associated with window B would come mainly from speaker 3. This scheme would work equally well for speech, and other complex sounds, as well as for more primitive sounds such as "beeps". Window A is of width dx and height dy. The left hand edge is distance x from the origin and the bottom edge is distance y. Audio circuitry is provided which comprises sets of four variable gain amplifiers aG1 to aG4 and bG1 to bG4 for each window and adding units 5 for each loudspeaker. In providing sound corresponding to window A the following steps are taken: In software: 1 The centre of the window is calculated, i.e. (x + dx/2), (y + dy/2). This will give the screen co-ordinates of the centre of the window. For example, if the top left hand corner of window A was 50,50 and the x and y offsets 150 and 100, then the centre of the window will be (50 + 150/2), (50 + 100/2), i.e. 125, 100. 2 With reference to the size of the screen determine the distribution over the four speakers, and thus the gain for the amplifiers (aG1, aG2, aG3, aG4). The distribution of the sound left and right (i.e. between the vertically aligned pairs of speakers 1 and 4, 2 and 3) will be in the same ratio as: width of the screen : x position of centre of the window If we assume the size of the display is the same as VGA screens (768 x 480), then the width of the screen is 768 and the height 480. If the x co-ordinate of the centre of the window is 125 then the ratio between speakers 1 & 4, and 2 & 3 (i.e. between left and right) is 84% to the left hand speakers and 16% to the right hand speakers. If the y co-ordinate of the centre of the window is 100 and the height of the window 480, then by the same method the ratio between speakers 1 & 2 , and 3 & 4 (i.e. up and down) is 79% is to the upper speakers and 21 % to the lower speakers. Now we have the percentages up and down, and left and right we can work out the percentage of the sound going to each of the four speakers. For example, of the 84% of the sound going to the left hand speakers 79% of this goes to the upper left hand speaker and 21% goes to the lower left hand speaker. Therefore, 66% (79% of 84%) goes to speaker 1 and 18% (21% of 84%) goes to speaker 4. Using the same method the percentage going to speaker 2 and 3 is 13% (79% of 16%) and 3% (21% of 16%). left right 84% 16% up 79% 66% 13% down 21% 18% 3% These figures can then be used to control the variable gain, aG1, aG2, aG3, aG4. In hardware: The hardware would be in the form of a card for the IBM PC-AT class machine. 1 The incoming audio is split into four and fed into four amplifiers. 2 The variable gains, aG1, aG2, aG3, aG4, calculated in software control each amplifier. 3 The outputs of the amplifier are added to the amplifier stages of the other channels in an adder. 4 The adder connects to the speaker. In the diagram overleaf only two channels are shown, however, a separate set of amplifiers is needed for each channel present.

Claims: An audio system for a visual display unit (VDU), the system comprising a plurality of loudspeakers distributed around the VDU, audio circuitry for driving the loudspeakers including means to allow a sound source signal to be variably distributed to the loudspeakers in amplitude and/or phase characterised in that the audio system is associated with a computer programmed to display an image relating to a sound source on a screen, wherein a particular region of the screen is devoted to the image, and wherein the screen co-ordinates of the image are processed to provide a control input to the audio circuitry whereby sound is generated which appears to emanate from a position having a predetermined relationship with the position of the image. An audio system according to claim 1 wherein the sound is generated so as to appear to emanate from the position of the corresponding image. An audio system as claimed in claim 1 wherein the apparent position of the sound source is further from the centre of the screen than the position of the corresponding image. An audio system as claimed in any of claims 1 to 3 wherein the computer program is a conferencing program running in a windows environment and respective users have respective dedicated screen areas, the sound inputs from the users being appropriately spatially matched to those areas An audio system as claimed in claim 1 comprising four loudspeakers positioned at respective corners of the screen.

Inventors: GALE STEPHEN, GALE, STEPHEN, GALE, STEPHEN, C/O HEWLETT PACKARD LIMITED
Applicants: HEWLETT PACKARD CO, HEWLETT-PACKARD COMPANY
Application year: 1990
Main classification: G06F3
IPC codes: C02F11, C02F3, G06F3