WO1998001197A1

WO1998001197A1 - Sound effect mechanism

Info

Publication number: WO1998001197A1
Application number: PCT/GB1997/001745
Authority: WO
Inventors: George Marmaropoulos
Original assignee: Central Research Laboratories Ltd
Current assignee: Central Research Laboratories Ltd
Priority date: 1996-07-04
Filing date: 1997-06-30
Publication date: 1998-01-15
Anticipated expiration: 1999-01-04
Also published as: GB9614078D0

Abstract

A listener-interactive audio game mechanism employing audible sound effects comprises sound reproducing means (20, 36, 38, 40, 42) for producing, without visual cues, audible sound effects (for example the sound of a flying insect) in three-dimensional sound. The sound effect is located in a three-dimensional space surrounding the listener. The sound reproducing means (20, 36, 38, 40, 42) also generates an object, such as another audible sound (for example a virtual catching device) at another location in the space and the listener moves the object relative to the sound effect to attain a predetermined relationship relative to the sound effect in response solely to audible cues present in the sound effect.

Description

Sound Effect Mechanism

This invention relates in particular to interactive mechanisms employing audible sound effects, and more generally to a game, relaxation, therapeutic, educational, learning, demonstration, simulation or the like mechanism providing audible sound effects.

Games based on audible sound effects are known, see for example US-A-4,320,901 which describes a game in the form of a bomb-like housing and containing a keyboard. Various sound effects are produced, and the keyboard is operated with a view to stopping the bomb exploding. US-A-4,207,087 describes a game having an elementary keyboard and based on the production of random sequences of tones. A player is required to listen to the tone sequence and to attempt to reproduce the tone sequence.

Video games for PCs and arcade machines are very popular and represent a big market for the software and hardware industry. Great effort and money is spent in developing new powerful chips in order to achieve high quality realistic 3-D graphics and animation. So far, only very powerful and expensive machines are able to achieve this, and they are usually very big and certainly not portable. Sound effects play an important role in these games, but only in enhancing the effectiveness of the graphics. At present, most CD- ROM games give video high priority over audio, such that the audio is often monophonic in order to occupy minimum storage capacity. Even on a very atmospheric game like Broderbund's "Myst", the sound is mono. However, stereo sound is becoming more and more widely used as people buy bigger speakers. A recent game is Sid Meyer's Civilization] 2 (Civ 2), which uses stereo enhancement to spread out the stereo, ambient sounds.

European Patent Application 0378386 is another example where a video-game is provided with an internal loudspeaker through which monaural sound is played. Optionally, headphones can be used, and in this case a pseudostereophonic sound is generated. In both modes of operation, the sounds are used simply to enhance the visual image and the sounds are not created as three dimensional sounds. US Patent 4,281,833 discloses a non-visual ball and paddle game which is played through the medium of sound. Ball location paddle position and playing field are defined by variations in volume, tone pitch frequency and stereo separation by means of stereo head phones worn by the listener. The game disclosed in this U S Patent exploits essentially a two dimensional sound field. It is only possible to determine whether the ball is moving towards or away from the player (tone/volume changesO and/or whether the ball is to the left or right of center (stereo separation) In order to intercept the sound- ball, each player is provided with a full-height paddle which he can move only to the left or right along a base line. It is not possible to determine whether the trajectory of the ball is high or low and whether it is moving diagonally from say upper left to lower right. Furthermore, the U S Patent does not disclose the concept of creating a virtual three dimensional space and creating an environment where the player experiences the sensation of being immersed interactively in the virtual three dimensional space.

The present invention is based on the recognition that our proprietary Sensaura (Registered Trade Mark) three-dimensional sound technology, for example as described in our copending patent applications WO95/15069 and WO94/22278, has the ability to localise sounds in three dimensions with a high degree of accuracy for a listener. The effect of this is that a sound source, such as music or a recorded noise, can be processed and then replayed via headphones or a pair of loudspeakers such that the sound is perceived by the listener to originate from precise locations in a three-dimensional space surrounding the listener as determined by the signal-processing algorithms. In accordance with the invention such technology provides the basis for a system based solely or mainly on audible effects wherein the aim is to estimate the position and/or direction of a sound in three-dimensional space, and to position and/or direct an object (real or imaginary), which may be another audible sound, a visible icon, or an imaginary location of the user, in response to this estimate.

Thus in accordance with the invention there is provided a mechanism for relaxation, therapeutics, education, learning, demonstration, simulation, playing a game, or the like, comprising operable to reproduce, in the absence of visual cues, audible sound effects, the or each of which, is perceived by the listener to be at a location having three orthogonal co-ordinates in a three dimensional space surrounding, the listener object generating means for generating on object located at a second location in said space having three orthogonal co-ordinates, and object-moving means operable in response to input from the listener derived solely from cues in said the, or each sound effect to move the object relative to the, or each, sound effect.

In accordance with the invention, the object to be positioned by the user may comprise a further audible sound, which, depending upon the rules of the game or other procedure, the player attempts to locate in a predetermined manner with respect to the sound effect. Alternatively the object may comprise a visible icon or other visible token to be positioned in a three-dimensional display, the position of the icon bearing a predetermined relation to the estimated position of the sound effect. The object may be an imaginary object, present only in the user's imagination, such as the position of the user in an environment created by the sound effects. The user, by means of the user operable object- moving means attempts to position himself in a predetermined relationship to that of the sound effect, which may in turn lead to a "scene-shifting" where the nature of the sound effects change, as if the user is walking along a path. To this end background music may be added to augment the aural impressions of the user's location.

The transducer means preferably comprises headphones or earphones for reproducing sounds from the audio signals; alternatively, loudspeakers may be employed, in which case it is necessary to employ cross-talk cancellation to ensure the full binaural effect.

Binaural technology is based on recordings made using a so-called "artificial head" microphone system, and the recordings are subsequently processed digitally. The use of the artificial head ensures that the natural three-dimensional sound cues - which the brain uses to determine the position of sound sources in three-dimensional space - are incorporated into the stereo recording. Subsequent signal processing of the binaural signals anticipates the transaural crosstalk which occurs when listening to the recordings via loudspeakers, and ensures that this transaural crosstalk is cancelled. Crosstalk occurs when an audio signal intended for one ear of a listener is also received by the other ear, and its cancellation ensures that the three-dimensional cues are effective on playback of the material, such that the brain can interpret the cues correctly. Without such processing, the recordings do not reproduce their three-dimensional attributes through loudspeaker auditioning. Crosstalk cancellation is described more fully in our copending

Patent Application No WO94/22278.

For the purposes of the present specification, the term "binaural signals" is intended to mean two-channel or stereophonic signals which include one or more components representing audio diffraction effects created by an artificial head means positioned between a pair of spaced apart microphones. The artificial head means may be, as is common, a precise model of a human head and torso with microphones in the ear structures; alternatively it may be something far less precise, for example a block or sheet of wood positioned between a pair of spaced microphones, which nevertheless creates diffraction signals from the source of sound signals; it may also be, as described more fully below, an electrical synthesis circuit or system which creates from an existing mono or stereo signal, stereophonic signals which include such diffraction signal components. As stated above, it is necessary when such signals are reproduced through loudspeakers that the signals have undergone processing for crosstalk cancellation, and preferably the "twice-through-the-ears" effect in order to recreate realistic three-dimensional sound images; this is fully described in our International Application Nos. WO94/22278 and WO95/ 15069. The content of our copending Patent Applications WO95/15069, WO94/22278 are incorporated herein by reference thereto.

The source of audible sound effects may comprise a CD ROM, floppy disc or other data storage media containing one or more files with a basic library of sounds for playing a desired game. These sounds may be in compressed or coded form. A processor may access the file for selecting one or more sounds for playing, in which case the sound information may be sent to a binaural processor for producing stereophonic binaural audio signals for reproduction. In addition an audio synthesis and tone generator circuit may be provided, so that a basic code for the sound may be issued from the processor, which causes the synthesiser to produce the desired frequencies and harmonics, which are then subject to binaural processing. The binaural processor produces, by means of appropriate filters with appropriate coefficients, binaural signals. In response to production of the sound, a user may, by use of a joystick and/or other appropriate controls, provide signals to the processor indicating that a further sound or sound sequence should be produced at a further location. Thus further sound elements are retrieved from store and fed to the binaural processor, where the coefficients of the filters are appropriately modified to produce a sound which is to be reproduced at the further location.

Where the invention is embodied as a game, there may be one or more sound effects that one or more users of one or more groups, can move (sequentially or simultaneously) in three dimensions, and other sound/effects that the system or other user or users can move in the same three dimensional space and at the same time. The interaction between these sounds, which according to the theme of a game could be following, chasing, hitting, matching, identifying, triggering, avoiding, or just listening, involves the user's input and skills and could dynamically change the course of the game.

One practical embodiment of the invention comprises:

Hardware

• A small, possibly portable, module able to accept some form of data storage media e.g. CD ROM, PCMCIA cards, discs. The unit will have an audio output.

• A user input device e.g. a joystick with at least 6 different actions namely forwards, backwards, left, right, upwards and downwards. An additional "hit" button is also desirable.

• Headphones or earphones or a pair of speakers.

• Optional means for covering the eyes in order to enhance concentration.

Software: three possibilities:

1. The system moves a sound (Sc) in a 3-D space. The player moves an object (Op), which could also represent himself, in the same space, in order to interact with Sc. 2. As above, but in this case the player moves a sound (Sp) which represents an object or himself. Sp could either help the player to locate his orientation or can make player "visible" to the system which then acts against or for him.

3. As in the above two cases, but now more than one players can be involved in the game playing either against each other or in teams or against the system. The game can also be played over a network of systems (machines) like the Internet.

The concept of a very simple game, which falls into category 1. comprises a virtual flying insect like a bee, fly, or mosquito is flying around the head of the player who stays still. The player can hear and locate the position of the insect by its sound and by means of a joystick, moves an object (a virtual catching device) which makes some kind of sound (e.g. Chinese chopsticks with a "click-click" sound). When the player thinks that the catching device is at the same position as the flying insect, he hits the button. At that time the system compares the x, y, z coordinates of the insect's sound with the coordinates of the catching device, takes into account the dimensions of the catching device and calculates whether the player "caught" the insect or not. A scoring system according to the difficulty of the task can also be introduced. For example, catching the insect while moving will give you more points than catching it while it is steady. Another possibility would be for the user to choose the degree of skill required by selecting different insects and catching devices. For example, catching a big fly would be easier than catching a small mosquito, or using chopsticks would obviously be more difficult than performing the same task using a net or a spray can and so on.

It is also possible to connect a monitor to the device that will allow the user visual feedback after trying to catch the flying insect. For example the monitor can show how far or close the catching device was from the insect when the player hit the "catch" button.

Using the same hardware, but more sophisticated software, other interesting concepts of games can be introduced, for example: the player moves himself by means of a joystick in a dark space surrounded by objects and creatures. He has to follow an invisible character, such as a ghost, which is played by the system. The only way to follow the invisible character is to follow the sound of its footsteps. Wearing headphones the player can estimate the direction and the distance of the sounds. The sound texture of the footsteps changes as the "ghost" steps on different floors, ground, climbs stairs. Sounds of creaking wooden floorboards, water, dragging chains, sand, can all add to the creation of an imaginary space. Player and "ghost" walk through a labyrinth of different stories.

If, at a junction, the player misses the "ghost", after a few seconds a sound like a voice or laughter will indicate the correct direction. If the player is confused he can use one of a limited amount of help advices. These would be in a form of soft whispers in the ear.

The aim of the game could be that the player, following the "ghost", must find the right exit within a certain amount of time. If successful, the exit could lead to a "paradise" space. Ambient sounds of waves, or waterfalls, the whisper of the forest and birds will reward the player who can then move to a more difficult stage of the game and so on. While the player moves in the darkness, he is likely to bump into objects and make other accidental noises. That makes him "visible" to "bad" creatures who then attack him or throw stones at him. The player hearing the sounds of oncoming dangerous objects must estimate where they come from and try to avoid them.

As in the previous example, visual feedback can also be introduced by connecting a display. The display would display graphics of the virtual environment.

Another concept, which falls into the third category of scenarios, is a game similar to "blind man's bluff which could be played by two or more players. Each player wears headphones and has a joystick. One is playing the "blind man" so he hears all the sounds made by the other players and he tries to "catch" them. The others can hear only the sound coming from the "blind man" and try to avoid him. Each player makes a particular sound (selected by the player) which is randomly and automatically produced in order to provoke the "blind man".

If a monitor is added then the person playing the "blind man" must cover his eyes and wear headphones. There is no need for the other players to wear headphones as they can watch all the player's positions on the screen. The "non-blind" participants can be caused to move more slowly than the "blind" player, in order to balance their tactical advantages. Other possible applications

Apart from the game opportunities, the system can also be used for the following applications:

• Training. For military or police purposes, or for training people blinded after illness or accidents, in order to improve awareness and sound perception.

• Psychological interventions for therapeutic purposes.

• For educational purposes.

• Another important application is for "interactive relaxation" or "interactive acoustic experiences" (e.g. lost in the jungle, a trip underwater or in a rain forest, etc.). In the latter case, the user would move himself through an acoustic environment choosing to stay or move on by being attracted by sounds that surround him. Different sounds can cause different emotions and different visual images in the brain and therefore they can create very exciting and new experiences. If the various acoustic elements are available by the processor unit, these could be selected randomly, but in an appropriate way, such that the listener floats through a virtual acoustic environment, and it is different each time the system is used, e.g. through a primeval forest, with passing dinosaurs, waterfalls, etc.

The main advantage of this system is that the necessary power needed for animation and high quality realistic graphics is shifted from the machine to the human brain which is able to translate the audio environment into an imaginary visual one in a way which is unique for each individual. Past experiences, emotions, personality and other subjective factors can influence the impact of the game opening up vast opportunities for a whole new gaming experience. And without the need of high resolution graphics and therefore the need of vast memory and speed, the system can be portable and that means that a new virtual reality environment can be experienced in places never before possible. On the train, at the park, or at home lying on bed or even at work during a break, people will be able to be immersed in a another ideal world where they can play a game or simply relax or even taste an exotic adventure. Future attachments to the system like voice recognition as an alternative or addition to the input device will create even more opportunities.

Video games and Virtual Reality are unknown things to blind people who now will be given the opportunity to enjoy and challenge themselves in a virtual world which is so close to theirs; a world of sounds.

Brief Description of the Drawings

A preferred embodiment of the invention will now be described by way of an example with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a game playing mechanism, in accordance with the invention;

Figure 2 is a block diagrammatic view of the components of a preferred embodiment of a game playing mechanism; and

Figure 3 is a flow chart for an audio game, for playing with the mechanism of Figure 2.

Description of the Preferred Embodiment

Referring now to Figure 1 , there is shown a game playing mechanism in accordance with the invention in the form of a portable unit 2 including a CD player housing 4 and a control panel 6. The control panel 6 includes push button controls 8 for starting the game, adjusting volume, etc, and microphone and earphone/ headphone sockets 10. Headphones 12 are shown connected to socket 10. A joystick 14 mounted in panel 6 is capable of backward/ forward motion for adjustment in a vertical plane of sound perceived through the headphones 12. A rotatable button 16 at the top of the joystick permits sound position adjustment in the horizontal plane. A trigger button 18 is employed in playing a game, as will become clear below. The unit shown in Figure 1 is specifically designed for use with the game illustrated in Figure 3. For other games, or when the unit is used as a relaxation device, the unit will be appropriately modified, for example by permitting further degrees of movement of the joystick.

Referring now to Figure 2, there is shown the various parts of the unit of Figure 1, indicated by the dotted lines 20. A CD-ROM drive 22 is coupled via a CD-ROM interface 24 to a central processing unit, CPU 26. Drive 20 accept a CD-ROM 28 which carries one or more games programs and audio files for sound sources (both mono and stereo format). CPU 26 is also coupled to a RAM 30 which, in use, stores program and audio data.

One or more user operable input devices 32] ...32_n preferably corresponding to the joystick 16, but more generally any joystick or rollerball are coupled through an input device interface 34 to CPU 26. Input devices 32 include a switch mechanism (18 of Figure 1) for indicating a "hit" or "action" condition. In other arrangements, some joysticks feature this switch as a button on top, or as a trigger on the front. Some have one or more separate buttons on the base of the unit. Some input devices use keypads, each with a pair of four-way tiltable thumbrests and several "fire" buttons, A 4-direction keypad is especially useful if movement is restricted to North, South, East and West in order to simplify matters and restrict the character to a maze of corridors, A simple joystick may not always provide an intuitive way of moving around in a 3D space especially for the concepts where the player changes all three polar coordinates ( not only the direction but also the distance from the sound). Therefore 3D input devices may be used. The term user operable device also covers keyboards and even more sophisticated devices related to Virtual Reality like gloves, movement detection devices.

CPU 26 provides instructions for sound production at assigned locations in three dimensional space to a Digital Sound Processor 36, which provides sound localisation and sound multiplexing. An audio synthesiser and tone generator 38 is coupled to processor 36. Depending on the sound type that CPU 26 requires production, processor 36 will retrieve an appropriate synthesised sound from generator 38. Such synthesised sound is then subject to localisation at a desired location as dictated by CPU 36.

This is done by applying the sound through left and right FIR filters having a selected number of taps and scaling coefficients in order to recreate the exact head-related transfer functions (HRTF) for a particular sound location. These coefficients are determined in advance, and the filter coefficients are changed by means of look-up tables in order to generate stereophonic binaural signals which represent sound at a particular location.

These binaural signals, L and R are fed to headphone drivers 40ι ...40_n for driving headphones 42 j 42_n , for wearing by one or more game players. In the case where the sounds are reproduced over loudspeakers (not shown) the binaural signals L and R would be subject to cross-talk cancellation in a unit 38, indicated in dotted lines for eliminating the effect of a signal destined for one ear of the listener also arriving at the other ear, as explained fully in our copending Patent Application Nos WO94/22278 and

WO95/ 15069.

One or more microphones 44ι...44_n are coupled through an amplifier and A/D converter 46 to CPU 26. A user control 48 (6 in Figure 1) which may be in the form of a keyboard provides various supervisory functions, such as power on/off, save game, headphone/loudspeaker option, pause, volume control, reset/start, and may include an LCD display for displaying such items as elapsed time, score position, battery status, help maps.

An infrared remote communications panel comprises a receiver 50, a transmitter 52 and a communications unit 54 coupled to CPU 26. A serial bidirectional network interface 56 is coupled to CPU 26 and provides a connection to the Internet or to a PC for downloading or saving of games. Additionally this could link two or more games together, such that a number of players can link games together in the same room ( from bed to bed in a hospital ward).

Referring now to Figure 3, there is shown a software flow chart for an "INSECT- CATCHING 3-D AUDIO GAME". The game is played as a sound representing the flight of an insect taking a random path in three-dimensional space. The player has to catch the imaginary insect by means of an imaginary catching device, e.g. chopsticks, before a time period elapses. He does this by estimating the position of the insect sound and attempting to collocate the sound of the catching device in the flight path. In the flow chart, the following symbols are used:

Si = insect's sound Θi(azimuth angle), Φi(elevation angle), Di(modulus of vector) = polar coordinates of Si

Θit, Φit = tolerances of insect's sound polar coordinates

Sp = Player's catching device sound

Θp(azimuth angle), Φp(elevation angle), Dp(modulus of vector) = polar coordinates of Sp Θpt. Φpt, Zpt = Tolerances in polar coordinates of sound of catching device.

Di = Dp = D = Standard. Both sounds move only on the surface of a sphere with D radius. The sphere surrounds the player. tm = time in which the insect's sound moves ts = time in which the insect's sound is still tmmin = minimum time for insect's sound movements tmmax = maximum time for insect's sound movement tsmin = minimum time for halting the insect's sound movements tsmax = maximum time for halting the insect's sound movement tmmin≤ tm < tmmax tsmin≤ ts≤ tsmax

Referring now to Figure 3, in step 60, which is a preparatory stage before playing the game, the player selects from a menu the type of catching device and the type of insect, thus defining Θpt, Φpt, Θit, Φit. In step 62, the game is started with the player's device at zero, where Θp = Φp = 0, and (step 64) t = 0. In step 66, a value is selected by means of an algorithm for the duration of the duration of the insects flight tm., and in step 68 a further algorithm selects Θi, Φi values in order to generate a random path in space. Both such algorithms would have a randomised nature, but would be such as to give a degree of realism to the flight of the insect.

Thus in step 68 , a sound is generated so that the insect moves in its flight path. In step 70, the player by means of joystick 14, changes Θp, Φp so that Sp moves to a position desired by the player to correspond with the position of the insect. In steps 72, 74, 76 the duration of the flight path is incremented if the player has not pressed "catch" button

18. If the flight path time has reached tm, then as shown in steps indicated collectively by

78, the insect remains still for a period ts. In step 80, a check is made whether the player has pressed the "catch" button, and if so, as shown in step 84, the values Θi, Φi, Θp, Φp are recorded at the time the catch button was pressed. From these values, a calculation is made to see whether the player caught the insect (i.e. these values are sufficiently close); in step 86 the values Θ = IΘp - Θil, Φ = IΦp - Φil are calculated and in step 88, the values Θ < Θpt + Θit, Φ ≤Φpt + Φit. If these inequalities are FALSE, then the player returns to the start of the game, but if the inequalities are TRUE, then in step 90 the player is rewarded with for example the sound of the dead insect dropping down. A decision can then be made in step 92, whether to quit the game or play another round.

Claims

1. A listener-interactive mechanism employing audible sound effects comprising, sound reproducing means operable to reproduce, in the absence of visual cues, audible sound effects, the or each of which, is located at a location having three orthogonal coordinates in a three dimensional space surrounding the listener, object generating means for generating an object located at a second location having three orthogonal co-ordinates in said space, and object-moving means operable in response to input from the listener derived solely from cues in said the, or each, sound effect to move the object relative to the, or each, sound effect.

2. A mechanism according to claim 1 wherein there is provided sound-moving means operable to move the, or each, sound effect to different locations in said space.

3. A mechanism according to claim 2 wherein the sound-moving means is operable to move the, or each, sound effect to different locations relative to the movement of the object.

4. A mechanism according to any one of claims 1 to 3 wherein the object comprises one or more audible sounds which are distinctive compared with said sound effects.

5. A mechanism according to any one of claims 1 to 3 wherein there is provided a display means for displaying images and the object is a visual image displayed on the display means.

6. A mechanism according to any one of the preceding claims wherein the sound reproduction means comprises a digital signal processor having an input for receiving binaural audio input signals, a filter means for applying head related transfer functions to said input signals, an output means for producing binaural output signals and transducer means for receiving said output signals and producing the said audible sound effects.

7. A mechanism according to claim 6 wherein the transducer means comprises a pair of spaced loudspeakers.

8. A mechanism according to claim 6 wherein the transducer means comprises a pair of headphones.

9. A mechanism according to any one of the preceding claims wherein the object represents an imaginary location of the listener in said space.

10. A mechanism according to claim 6 wherein there is provided a source of audible sound effects comprising a set of data in coded format, an audio synthesiser and a tone generator for generating sound signals from an item of such coded data, and means for applying such sound signals as input signals to said processor.

11. A mechanism according to any one of the preceding claims comprising at least one further object-moving means operable in response to input from a further listener to move a further object relative to the, or each, audible sound effect.

12. A mechanism according to claim 6 wherein the processor includes filter means with adjustable coefficients which are operable to change the apparent location of the, or each, audible sound effect relative to the listener.

13. A method of playing a game employing a mechanism constructed in accordance to any one of the preceding claims the method comprising the steps of

(a) providing by means of the mechanism, one or more of said audible sound effects the, or each of which, is located at a predetermined location, in said space,

(b) defining one or more predetermined objects,

(c) positioning the or each, object at a location in said space spaced from the location of the, or each, audible sound effect. (d) moving the, or each, object in response to the listener's estimate of the location of the, or each, sound effect.

(e) repeating steps (c) and (d) until the location of the, or each, object bears a predetermined relationship to the location of the, or each, sound effect, or until an assigned time interval for the game has expired.

14. A method according to claim 13 wherein the sound effect comprises a sound representing an insect in flight, and the predetermined object comprises a sound representing a device for catching the insect.

15. A method according to claim 13 wherein the predetermined object represents the player, and positioning of the object causes changes in a created audible sound representing the object thereby to represent a change in the location of the player in said space, the game being completed when the listener is positioned at a predetermined location relative to the sound effect as determined by the created sounds.

16. A method according to any one of claims 13 to 15 wherein there are a plurality of players each employing a respective object moving means for effecting steps (c) and (d).

17. A method of using a mechanism constructed in accordance with any one of claims 1 to 12 comprising the steps of

(a) providing by means of the mechanism, one or more of said sound effects whereby to create an impression to the listener of a predetermined environment,

(b) defining an object representing the location of the listener in said space at a location spaced from the one, or more, sound effects.

(c) moving the object in response to the listener's impression of where he is in said environment thereby to change the created sound effects to change the nature of the environment,

for as long as the listener desires, or for a predetermined time,

18. A mechanism substantially as herein described with reference to the accompanying drawings.

19. A method of using a listener interactive mechanism substantially as herein described with reference to the accompanying drawings.