GB2354872A

GB2354872A - Noise simulator

Info

Publication number: GB2354872A
Application number: GB0018409A
Authority: GB
Inventors: Phillip R Bone
Original assignee: VIDEO TECH DESIGNS PLC
Current assignee: VIDEO TECH DESIGNS PLC
Priority date: 1999-07-30
Filing date: 2000-07-28
Publication date: 2001-04-04
Also published as: GB0018409D0; GB9917784D0

Abstract

A noise simulator for a vehicle, including a sound generator which, dependent on engine speed, is adapted to introduce into the passenger compartment a sound having a content and waveform selected to represent a chosen sound different to that produced by the vehicle in which the noise simulator is installed.

Description

2354872 Title: Noise simulator

Field of invention

This invention concerns noise simulators particularly for use in motor vehicles and the like.

Background to the invention

It is known to simulate noise in association with computer games, driving simulators and fairground and arcade games. It is also known to link the pitch and sound quality to the controls provided in such environments so that as the controls are altered, the sound is adjusted accordingly so as to simulate acceleration or braking, and lift-off or landing in the case of an aircraft or helicopter.

It is an object of the present invention to provide a sound simulator for use in an actual vehicle as opposed to the use of such devices in association with driving or flight simulators or games.

Summary of the invention

According to one aspect of the present invention, sound generating means is provided adapted to be mounted on or in a vehicle particularly a motor car, and which is further adapted to introduce sound into the passenger compartment of the vehicle, the pitch of which is related to the vehicle engine speed and the harmonic content and waveform of which is selected so as to represent a chosen vehicle sound.

In one example the selected sound may be of a class of vehicle quite distinct from that to which the device is fitted. Thus for example the sound within the passenger compartment of a saloon car may be modified by the device so 2 as to resemble that of a high performance sports car.

Sound signals for producing the simulated sound are preferably electrically generated by a signal generator, the operating frequency of which is proportional to the engine speed of the vehicle into which the device is fitted, and the electrical signals so generated may be amplified and reproduced within the passenger compartment of the vehicle using one or more loudspeakers mounted within the passenger compartment.

According to another aspect of the invention, the simulated sound may be quite distinct from a motor vehicle, but nevertheless controlled as regards frequency, repetition rate or other regularly occurring features thereof in relation to the speed of the vehicle, or the engine.

Examples are a sound of a motorbike, a steam engine, jet engine, spaceship/rocket motor or horses hooves.

where the vehicle has an integrated sound system with two or four or more loudspeakers mounted within the passenger compartment, at least the loudspeakers may be utilised to reproduce the simulated vehicle sound within the passenger compartment.

Where a power amplifier having at least one accessible input socket is provided as part of the integrated sound system within the vehicle for powering the loudspeakers, the signal generator output signal may be supplied to the input of the amplifier.

In a more preferred arrangement, a mixer unit is provided whereby other sound signals from audio sources such as a CD player, a cassette player or a radio may be mixed with signals from the signal generator to a greater or lesser extent so that the one or the other takes precedence.

Where the vehicle includes a cassette player (either as a 3 stand-alone unit or incorporated into a radio receiver), a known cassette adaptor may be utilised for introducing the signals into the sound system of the vehicle without the need to gain access to line inputs of a power amplifier. Such known adaptors consist of a special audio cassette moulding adapted to be fitted into a cassette player in place of a standard cassette, containing appropriate electrical circuits and with a lead having an appropriate jack plug or other audio connector device which allows the device to be plugged into the output of a signal source (typically a CD player for which purpose they were designed in the first place), and for generating signals which can be picked up by the tape head in the cassette player to provide audio signals for amplification and distribution within the vehicle.

According to a further preferred feature of the invention, the signal generator may itself be adapted to receive signals from a source such as a radio or CD player or the like, and supply as an output signal either the sound simulator signals or the radio or CD player audio signals, or a combination of two or more of the sources for supply to a power amplifier for distribution via the loudspeakers in the passenger compartment.

In this event the device according to the invention would include input sockets and output sockets and audio leads with appropriate jack plugs and the like would be provided for interconnecting the unit with sound sources as aforesaid, and a power or booster amplifier such as is conventionally fitted within a motor vehicle to boost the output signals available from a standard car radio, cassette player or CD system.

Power for the signal generator and associated circuitry, may be derived f rom the vehicle 12 volt or 24 volt system with appropriate fuses and switches in line or a temporary connection may be provided for connection to the cigar 4 lighter socket which is now conventionally provided on most vehicles.

According to a further feature of the invention, the signals produced by the signal generator may themselves be modified by a selector to provide two or more different characteristic sounds so that the driver or passengers can select one of two or more different sound simulations depending on their mood or choice. Thus a system incorporating the invention could be adapted to produce vehicle sound simulation equivalent to a four cylinder rally vehicle, a six cylinder or eight cylinder sports vehicle, or a twelve cylinder sports/rally car, or any other sound such as motorbike, steam engine, jet engine etc as aforesaid.

In one embodiment of the invention, a signal generating device incorporates a volume control for adjusting the volume of the simulated sound which is to be distributed within the passenger compartment, a sound character selector to enable any one or two or more different sound simulations to be distributed within the passenger compartment of the vehicle, an ONIOFF switch and optionally a test button to allow a preselected frequency and volume escalation similar to that of an engine being revved or a horse accelerating, to be generated for distribution within the sound compartment to demonstrate to the user the character of the sound which as been selected.

Optional extras to the basic unit may comprise:

1. A rev counter display for indicating either digitally or in an analogue or clock face manner the engine revolutions per minute corresponding to the frequency of the sound being generated at any instant.

2. Selectable sound zones for example front, rear or driver seat only. Typically the selectable sound zone would introduce sound into the vehicle at the selected location within the passenger compartment so that as perceived by a driver or passenger sitting in an appropriate part of the passenger compartment, the sound will be that which would be perceived by that person if sitting in the vehicle whose sound is being simulated. This is of particular importance where the engine is located centrally or in the rear of the vehicle as opposed to the conventional forward position.

3. Circuit means may be provided to determine the rate of change of engine speed and dynamically modify the simulated sound accordingly.

4. In addition or alternatively, a throttle position sensor could be provided to produce more accurate and potentially more realistic sound simulation.

5. Additional circuit means may be provided to combine signals from a throttle position sensor and engine speed sensor to produce an engine loading signal the value of which can be adapted to adjust the volume and tone of the simulated sound which will obviously change in a real vehicle depending on the loading on the engine.

6. The invention may also provide a fuel economy display derived from the engine speed and throttle position to indicate to the driver (and other observers) whether the car is being driven economically or not.

7. Digital sampling techniques may be employed with digital storage of sound samples at different engine speeds while accelerating and decelerating and in the case of a powered vehicle at different throttle settings, all derived from an original vehicle or trot t ing/ cantering/ gal loping horse, the sound of which is to be simulated in another vehicle, and the signal generator selects the appropriate sample and uses that to generate a waveform of the appropriate pitch and amplitude having regard to the engine speed (and if provided, throttle setting) 6 A noise simulator according to the invention may be constructed from four different elements, namely an engine sensor, a timing generator, a sound simulator and an audio output device.

The engine sensor may for example comprise a simple conductor located in close proximity to one of the spark plug leads in the case of a petrol engine. Electrical signals induced in the cable (which may be wrapped around the spark plug lead for increased coupling), is amplified and shaped by an amplifier and pulse shaper within the engine sensor module.

other examples of sensor are:

(1) a sensor wire wrapped around a spark plug lead (2) a sensor wire around the high tension lead from the coil to the distributor cap (3) measuring the voltage directly across the "points" (4) a tap into an engine management system (5) sample and analyse "noise" on the cars electrical system (6) analyse the sound from a microphone in the engine bay (7) a magnetic or optical sensor "looking" at a rotating part of the engine.

Similar arrangements where appropriate can be applied to diesel and electric powered vehicles.

The timing generator conveniently comprises a frequency to voltage and voltage to frequency convertor although in the alternative, different sensing methods involving magnetic pick-ups in the engine and direct connections into a cars engine management system may be employed which would simplify and obviate some of the engine sensor and timing generator structural features previously mentioned.

A micro-processor or digital signal processor may be 7 employed to calculate the timing for the sound simulator, which latter may comprise an EPROM containing digitised audio sound samples from different vehicles and an audio digital to analogue convertor for producing a standard analogue waveform corresponding to the digital sound samples which are read out at the appropriate frequency depending on the timing generator output. Alternatively a plurality of analogue tone generators may be employed with a mixing circuit for amplifying the tones as required.

As previously described the audio output from the D to A convertor may be at a signal level or at a power level depending on whether the unit is designed to supply an input signal to a power amplifier or to directly drive one or more loudspeaker units.

According to another aspect of the invention, a method of simulating and introducing sound within a passenger compartment of a motor vehicle comprises generating electrical signals at a frequency corresponding to the rotational speed of the vehicle engine, waveshaping of the signals to produce a desired repetitive waveform, or generating pre-selected wave shapes from stored information (typically digitally stored information) for repetitively producing one of a plurality of different waveforms, and amplifying and reproducing the repetitive waveform as a sound signal within the passenger compartment using one or more loudspeakers located at appropriate positions within the passenger compartment thereof.

The invention also lies in a motor vehicle when adapted to generate sound signals characteristic of another motor vehicle or another mode of transportation within the passenger compartment of the vehicle, wherein at least the rotational speed of the engine is sensed and used to determine the frequency of a generated audio waveform the waveshape of which is appropriate to produce within the passenger compartment a sound which is characteristic of the 8 said other vehicle or other transportation device.

The invention also lies in a kit of parts adapted to be mounted within a motor vehicle and powered from the vehicle power supply, and at least a sensor for generating electrical pulses in response to the ignition pulses or in response to a sensor associated with a rotational device located on the vehicle engine or transmission shaft, and further adapted to be connected to loudspeakers already mounted within the vehicle or mountable within the vehicle to distribute audio sound within the passenger compartment, the characteristics of which are selectable by a selector forming part of the kit of parts and the f requency of the sound is controlled by signals derived from the said sensor.

The invention also lies in a car radio or combined radio cassette player, or radio/CD player or CD player adapted for fitting within a vehicle, having incorporated integrally therein some or all of the component parts of a system incorporating the invention to generate a sound signal for distribution within the passenger compartment of the vehicle via loudspeakers associated with the radio, cassette, CD player or other device or other loudspeakers, instead of or in addition to sound signals from the radio, cassette or CD player, the signals being generated at a frequency proportional to the engine speed of the vehicle and having a character and quality selectable from two or more different waveforms, so as to produce within the passenger compartment, one or two or more different sounds corresponding to the sound which would be experienced within the passenger compartment if the vehicle were of another type of vehicle or other transportation device.

The invention also lies in a vehicle when modified as aforesaid.

The invention is of particular application to electric powered vehicles in which there is characteristically very 9 little engine noise, even when running at speed. By selecting a waveform for the sound to be reproduced in the passenger compartment, which will cause a sound similar for example to a motor car powered by an internal combustion engine to be introduced therein and linking the frequency and amplitude of the repetitive waveform to the electric motor speed so that it will produce a sound within the compartment which is similar to that which an internal combustion engine and associated exhaust would generate therein if an internal combustion engine were powering the vehicle under the same conditions, the driver may be assisted in appreciating the speed of the vehicle and, whether (for example in the case of a vehicle having a manual gearbox) a gear change is called for.

The amplitude and shape of the waveform may be controlled by a logic circuit comparing the throttle setting (indicating the power being conveyed to the motor) with the motor speed and/or vehicle speed, thereby to simulate light and heavy load conditions on the motor.

When linked to an electric powered vehicle having a gearbox, the frequency of the repetitive waveform may also be controlled to take into account the selected gear.

Description of examples

The invention will now be further described with reference to the accompanying drawings, in which:- Fig 1 is a block circuit diagram of a basic noise injection system providing a mono sound output; Fig 2 is a modification of the circuit diagram of Fig 1 wherein the noise injection system provides a stereo output; Fig 3 is a circuit diagram of the audio output and power supply section of the noise injection system; Fig 4 illustrates a throttle movement sensor for the noise injection system; Fig 5 illustrates an engine speed sensor for the noise injection system; Fig 6 shows a practical arrangement of the noise injection system when applied to a "V-car" product; and Figs 7 to 10 respectively illustrate four methods by which the practical arrangement of noise injection system can be installed in a motor vehicle.

Fig 1 is a block diagram of a basic noise injection system with a mono sound output. At the heart of the noise injection system is a micro controller 16 which has been programmed specifically for this application. There are three main inputs to the micro controller 16, namely the engine sensor input 12, the throttle position input 13, and two push- buttons 14 mounted on the front panel.

The engine sensor enables the micro controller to calculate the speed of the host car engine. An amplifier and level converter circuit 11 is used to condition the signal present at the circuit board terminals 10 and make it a suitable signal for the micro controller input 12. An engine sensor for a petrol engine car is shown in Fig 5. The sensor consists of a length of coaxial wire 128 with the screening removed from the final lcm or so to form a short aerial lead 126. This short aerial is not designed to make contact with any part of the car but simply to pick-up the noise radiated by the car ignition system. A plastics sheath double insulates the aerial lead 127 and forms a probe end. To improve the coupling between the engine sensor probe and the car ignition system, the probe is clipped over the insulation of one of the ignition leads 122 or 124. The micro controller 16 is programmed to accept the differently timed pulses from either the common high tension lead between the coil 125 and distributor 123, or from one of the spark plug leads 122. For engines without a conventional ignition coil and common high-tension lead, the probe can be attached to the centre of the distributor casing. Four, six and eight cylinder car engines can be measured using this method with the appropriate programming of the micro controller.

The engine sensor mentioned above will only work with petrol and gas car engines that have conventional ignition systems. other engine sensor schemes could be used, some of which would make it possible to measure the speed of diesel, electric or hybrid car engines. For example, an optical or magnetic (Hall effect) sensor with a toothed wheel attached to a rotating part of the engine, direct connection to the electronic engine management system, or calculating the engine speed by measuring the noise on the car electrical supply- To enhance the operation of the noise injection system a throttle position sensor has been added. This enables the sound output to be modified according to the position of the host car throttle pedal. For example, as the throttle pedal is pressed the stored engine sound could become louder, or it could change to make the sound of an engine working harder. When the throttle pedal is released the stored engine sound could make an over-running, or 'popping, sound. The simple throttle position sensor illustrated in Fig 4 consists of just one tilt switch. The tilt switch 102 is mounted in a rotating housing 100 and fixed to the mounting bracket 103 with a single central screw. A lead 101 connects the tilt switch to the circuit board in the noise injection system. The complete throttle sensor assembly 104 is attached to the throttle pedal arm by two straps 106. To help the user set up the device, a line pointing towards the car engine on the throttle sensor housing 105 indicates when the tilt switch is at 100 to the 12 horizontal. At this setting the tilt switch operates when most throttle pedals are pushed half way down. The user can adjust the switching point of the throttle switch by rotating the housing.

Other types of throttle position sensor are possible. For example, to increase the resolution more tilt switches could be added, or a potentiometer device could be fitted. To achieve a more accurate reading of engine load a vacuum sensor could be fitted to the engine inlet manifold and this signal relayed to the system.

In Fig 1 the basic noise injection system has two push buttons 14 mounted on the front panel. Pressing the DEMO button causes the stores engine sound output to ramp up and down as if the throttle pedal was pressed to 'rev' the engine. Pressing the SELECT button changes the state of the sound select bus 20. This alters the address of the EPROM sound store 23 and results in the unit producing a difference sound output.

To indicate the status of the unit to the user, the micro controller 16 drives a number of LED's which are mounted on the front panel 15. Typically these are: ON, RUN, THROTTLE, 1,2,3 and 4 but many other variations and labels are possible. The ON LED indicates that the noise injection system is switched on and powered up. The RUN LED indicates that the host car engine is running. The THROTTLE LED indicates that the throttle switch is on. The 1,2,3,4 LED's indicate which of the four stores sounds has been selected.

The micro controller 16 has three outputs. The sound select bus 20 changes the EPROM address so different sound outputs can be selected. The clock output 19 drives the EPROM address generator counter 21. The volume control output 22 is a high frequency pulse width modulated signal that switches the output of the EPROM on and of f using its /OE (output enable) input. The audio filter 25 removes any 13 unwanted digital switching frequencies that occur by using this technique. The EPROM data output is of f when the /OE line is high (+5V) and on when the /OE line is low. The output volume is adjusted by altering the mark space ratios of the /OE input between 0 and 100%. For example, when the volume control signal has a 50% mark space ratio the output volume is half the maximum.

By recording the original sound at a known engine speed and matching this with the data sample rate stored in the EPROM, it is possible for the stored sound to be clocked out of the EPROM at exactly the same speed as the host car engine and remain synchronised over a wide range of speeds. In the basic design one engine sound is used to cover the complete speed range of the host car engine. More elaborate designs could use a number of engine sound recordings, which are switched on in sequence as the host car engine speeds up. It is also possible to scale or offset the stored soundclock so that the recorded car sound does not match the host car engine speed exactly, but always stays in step.

To increase the number of sounds stored, or to lengthen the sound repeat time, more EPROM's could be added to the system. The system could also make use of various audio compression techniques such as ADPCM (Adaptive Pulse Code Modulation) or MP3 and incorporate special integrated circuits into the circuit to provide this facility. Other storage methods could be used such as flash memory and removable memory cards. New sound files may be downloaded f rom the Internet in a similar way to that used by MP3 audio players.

A stereo sound version of the noise injection system is shown in Fig 2. This uses two EPROM' s 51, 53 which are addressed and clocked simultaneously. Other schemes could be devised which multiplex the output of the EPROM to produce stereo sound.

14 The digital data out of the EPROM 23 is converted to analogue sound using a digital to analogue converter 24. An active filter 25 is used to remove the digital switching noise from the audio signal. The overall sound volume is adjusted using potentiometer 26. In the stereo version shown in Fig 2 there are two digital to analogue converters 54, 55, two sets of filters 56, 58, and a twin ganged potentiometer 57, 59.

The audio output and power supply section of the noise injection system is shown in Fig 3. The two way multipole push button 71 is shown in the of f position. When off, no power is supplied to the noise injection system circuit regulator 72 and the audio system is bypassed by connecting the loudspeaker output lead connector 74 directly to the audio input lead connector 73. When the push button is on, the noise injection system is powered up, the loudspeakers 88, 89 are disconnected from the audio outputs 73 and connected to the power amplifiers 78, 79. Also, any sound present at the audio inputs 73 from a radio, audio cassette player, CD player or MiniDisc player 85 connected to its loudspeaker leads 86, is then mixed with sound from the engine sound generator 75 using mixing circuits 76, 77 before being amplified by the power amplifiers 78, 79.

For temporary connection to the car audio system, a jack socket 84 is provided which supplies an attenuated signal via lead 90 to a cassette adapter 91. The attenuator consists of resistors 80 and 82 for the right hand channel and resistors 81 and 83 for the left hand channel. A cassette adapter is normally used to enable portable CD players to be heard via a Radio/Cassette player. In this application the cassette adapter enables the noise injection system to be played directly into a Radio/Cassette player without the user having to disturb the wiring in the host car.

Fig 6 illustrates a practical version of the noise injection system. The front panel has a large push button 150 which turns the unit on and of f. The rotary volume control 151 adjusts the sound level of the stored engine sound. Push button 152 runs the demonstration sound. Push button 153 selects alternative engine sound effects. A row of LEDs 154 indicate the status of the unit.

on the rear panel is a jack socket 160 which enables the unit to be connected to a cassette adapter 161. All other connections are bundled together and exit the unit via a rubber grommet in the rear panel 162. The engine sensor lead is 2- 3m long and the probe end is attached to an ignition lead inside the engine compartment (see Fig 5). The optional throttle sensor 164 is connected to the unit by a cable 1 -2m long and is attached to the car throttle pedal arm (see Fig 4). A lead fitted with a standard cigar lighter plug 165 normally supplies power to the unit but the plug could be removed and the wires connected directly to the car's electrical system for a more permanent installation. Loudspeakers 166 are connected to the four output wires. Four input wires are provided so that the loudspeaker outputs from a Radio/Cassette player 167 can be connected to the noise injection system and its sound mixed with the stored engine sounds.

Figs 7, 8, 9 and 10 illustrate four ways a commercial version of the noise injection system can be installed in a car.

Fig 7 illustrates the noise injection system 180 directly driving loudspeakers 181, 182 with just the stored engine sound output. The loudspeakers are in addition to any loudspeakers already fitted to the car.

Fig 8 illustrates the noise injection system 183 connected to an existing car Radio/Cassette player 18S using the optional cassette adapter 184. The sound is played through the existing loudspeakers 186, 187 connected to the 16 Radio/Cassette player 185.

Fig 9 illustrates how the noise injection system 191 can be installed with a Radio/Cassette/CD/Minidisk player 189 so that the stored engine sound is mixed with sounds from the Radio/Cassette/CD/Minidisk player. The connecting leads 190 are taken from the loudspeaker outputs of the Radio/Cassette/CD/Minidisk player and connected to the audio inputs of the noise injection system 191. Loudspeakers 192, 193 are the existing loudspeakers originally connected to the Radio/ Cass et te/ CD/Minidi sk player 189. When the noise injection system is switched off the loudspeakers are connected directly to the Radio/ Cassette/ CD/Minidi sk player, completely bypassing the noise injection system.

Fig 10 illustrates the noise injection system 195 fully integrated with a car HiFi system so the output sound volume is boosted through a separate power amplifier 199. Lead 196 connects the Radio/ Cassette/CD/Minidisk player to the noise injection system 197 and lead 198 connects the noise injection system 197 to the power amplifier 199. The loudspeakers 200, 201, 202 and 203 are connected to the power amplifier 199.

Claims

1 A noise simulator for a vehicle, comprising sound generating means adapted to be mounted on or in a vehicle particularly a motor car, and which is further adapted to introduce sound into the passenger compartment of the vehicle, the pitch of which is related to the vehicle engine speed and the harmonic content and waveform of which is selected so as to represent a chosen vehicle or other means of transport.

2 A noise simulator according to claim 1, wherein the selected sound is of a class of vehicle quite distinct from that to which the vehicle is fitted.

3 A noise simulator according to claim 1 or claim 2, wherein sound signals for producing the simulated sound are electrically generated by a signal generator, the operating frequency of which is proportional to the engine speed of the vehicle into which the device is fitted, and the electrical signals so generated are amplified and reproduced within the passenger compartment of the vehicle using one or more loudspeakers mounted within the passenger compartment.

4 A noise simulator according to claim 1, wherein the simulated sound is quite distinct from that of a motor vehicle, but nevertheless controlled as regards frequency, repetition rate or other regularly occuring features thereof in relation to the speed of the vehicle or of the engine.

A noise simulator according to any of claims 1 to 4, wherein, where the vehicle has an integrated sound system with two or four or more loudspeakers mounted within the passenger compartment, at least one or more of these loudspeakers is utilised to reproduce the simulated vehicle sound within the passenger compartment.

6 A noise simulator according to claim 5 wherein, where a power amplifier having at least one accessible input socket is proved as part of the integrated sound system within the vehicle for powering the loudspeakers, the signal generator output signal is supplied to the input of the amplifier.

7 A noise simulator according to any of claims 1 to 6, wherein a mixer unit is provided whereby other sound signals from audio sources such as a CD player, a cassette player, minidisc player or a radio are mixed with the signals from the signal generator to a greater or lesser extent so that the one or the other takes precedence.

8 A noise simulator according to any of claims 1 to 7, wherein, where the vehicle includes a cassette player (either as a stand-alone unit or incorporated into a radio receiver), a conventional cassette adapter is utilised for introducing the signals into the sound system of the vehicle without the need to gain access to line inputs of a power amplifier.

9 A noise simulator according to any of claims 1 to 8, wherein the signal generator is itself adapted to receive signals from a source such as a radio or CD player or the like and supply as an output signal either the sound simulator signals or the radio or CD player audio signals, or a combination of two or more of the sources for supply to a power amplifier for distribution via loudspeakers in the passenger compartment.

A noise simulator according to claim 9, wherein input sockets and output sockets and audio leads with appropriate jack plugs and the like are provided for interconnecting the unit with sound sources as aforesaid and with a power or booster amplifier such as is conventionally fitted within a motor vehicle to boost the output signals available from a standard car radio, cassette player or CD system.

11 A noise simulator according to any of claims 1 to 10, wherein power for the signal generator and associated circuitry is derived from the vehicle 12 volt or 24 volt system with appropriate fuses and switches in line, or a temporary connection may be provided for connection to the cigar lighter socket which is now conventionally provided on most vehicles.

12 A noise simulator according to any of claims 1 to 11, wherein the signals produced by the sifnal generator are themselves modified by a selector to provide two or more different characteristic sounds so that the driver or passengers can elect one of two or more different sound simulations depending on their mood or choise.

13 A noise simulator according to any of claims 1 to 12, wherein the signal generating means incorporates avilume control for adjusting the volume of the simulated sound which is to e distributed within the passenger compartment, a sound character selector to enable any one of two or more different sound simulations to be distributed within the passenger compartment of the vehicle, an ON/OFF switch and optionally a test button to allow a pre-selected frequency and volume escalation similar to that of an engine being revved or a horse accelerating, to be generated for distribution within the sound compartment to demonstrate to the user the character of the sound which has been selected.

14 A noise simulator according to any of claims 1 to 13, including a rev counter display for indicating either digitally or in an analogue or clock face manner the engine revolutions per minute corresponding to the frequency of the sound being generated at any instant.

A noise simulator according to any of claims 1 to 14, including selectable sound zones for example front, rear or driver seat only, the selectable sound zone introducing sound into the vehicle at the selected location within the passenger compartment so that as perceived by a driver or passenger sitting in an appropriate part of the passenger compartment, the sound will be that which would be perceived by that person if sitting in the vehicle whose sound is being simulated.

16 A noise simulator according to any of claims 1 to 15, wherein circuit means are provided to determine therate of change of engine speed and dynamically modify the simulated sound accordingly.

17 A noise simulator according to any of claims 1 to 16, including a throttle position sensor for producing more accurate and potentially more realistic sound simulation.

18 A noise simulator according to claim 17, wherein additional circuit means are provided to combine signals from a throttle position sensor and engine speed sensor to produce and engine loading signal the value of which is adapted to adjust the volume and tone of the simulated sound which changes in a real vehicle depending on the loading of the engine.

19 A noise simulator according to any of claims 1 to 18, including a fuel economy display derived from the engine speed and throttle position to indicate to the driver (and other observers) whether the car is being driven economically or not.

A noise simulator according to any of claims 1 to 19, wherein digital storage of sound samples at different engine speeds while accelerating and decelerating and in the case of a powered vehicle at different throttle settings, all derived from an original vehicle or trotting/cantering/galloping horse, the sound of which is to be simulated in another vehicle, and the signal generator selects the appropriate sample and uses that to generate a waveform of the appropriate pitch and amplitude having regard to the engine speed (and if provided, throttle setting).

21 A noise simulator according to any of claims 1 to 20, including four difference elements, namely and engine sensor, a timing generator, a sound simulator and an audio output device.

22 A noise simulator according to claim 21, wherein the engine sensor comprises a conductor located in close proximity to one of the spark plug leads in the case of a petrol engine.

23 A noise simulator according to claim 21, wherein the engine sensor comprises any one of:- (1) a sensor wire wrapped around a spark plug lead (2) a sensor wire around the high tension lead from rhe coil to the distributor cap (3) measuring the voltage directly across the "points" (4) a tap into an engine management system (5) sample and analyse "noise" on the car's electrical system (6) analyse the sound from a microphone in the engine bay (7) a magnetic or optical sensor "looking" at a rotating part of the engine.

24 A noise simulator according to any of claims 1 to 23, wherein a timing generator comprises a frequency to voltage and voltage to frequency converter.

A noise simulator according to any of claims 1 to 24, including a micro-processor or digital signal processor provided to calculated the timing for the sound simulator, which latter comprises an EPROM containing digitised audio sound samples from different vehicles and an audio digital to analogue converter for producing a standard analogue waveform corresponding to the digital sound samples which are read out at the appropriate frequency depending on the timing generator output.

26 A noise simulator according to any of claims 1 to 24, wherein a plurality of analogue tone generators are employed with a mixing circuit for amplifying the tones as required.

27 A method of simulating and introducing sound within a passenger compartment of a motor vehicle, which comprises generating electrical signals at a frequency corresponding to the rotational speed of the vehicle engine, waveshaping of the signals to produce a desired repetitive waveform, or generating pre-selected wave shapes from stores information (typically digitally stores information), for repetitively producing one of a plurality of different waveforms, and amplifying and reproducing the repetitive waveform as a sound signal within the passenger compartment using one or more loudspeakers located at appropriateb positions within the passenger compartment thereof.

28 A motor vehicle when adapted to generate sound signals characteristic of another motor vehicle or another mode of transportation within the passenger compartment of the vehicle, wherein at least the rotational speed of the engine is senses and used to determine the frequency of a generated audio waveform the waveshape of which is appropriate to produce within the passenger comparment a sound which is characteristic of the said other vehicle or other transportation device.

29 A kit of parts adapted to be mounted within a motor vehicle and powered from the vehicle power supply, and at least a sensor for generating electrical pulses in response to the ignition pulses or in response to a sensor associated with a rotational device located on the vehicle engine or transmission shaft, and further adapted to be connected to loudspeakers already mounted within the vehicle or mountable within the vehicle to distribute audio sound within the passenger compartment, the characteristics of which are selectable by a selector forming part of the kit of parts and the frequency of the sound is controlled by signals derived from the said sensor.

A car radio or combined radio cassette player, or radio/CD player adapted for fitting within a vehicle, having incorporated integrally therein some or all of the component parts of a simulator according to any of claims 1 to 26, to generate a sound signal for distrribution within the passenger compartment of the vehicle via loudspeakers associated with the radio, cassette, CD player or other device or other loudspeakers, instead of or in addition to sound signals from the radio, cassette or CD player, the signals being generated at a frequency proportional to the engine speed of the vehicle and having a character and quality selectable from two or more different waveforms, so as to produce within the passenger compartment, one or two or more different sounds corresponding to the sound which would be experienced within the passenger compartment if the vehicle were of another type of vehicle or other transportation device.

31 A noise simulator according to any of claims 1 to 26, when incorporated in an electrically powered vehicle.

32 An electrically powered vehicle according to claim 31, wherein, by selecting a waveform for the sound to be reproduced, a sound distinctive of a motor car powered by an internal combustion engine is introduced into the passenger compartment, and, by linking the frequency and amplitude of the repetitive waveform to the electric motor speed so that it will produce a sound within the compartment which is similar to that which an internal combustion engine and associated exhaust would generate therein if an internal combustion engine were powering the vehicle under the same conditions, the driver is assisted in appreciating the speed of the vehicle and whether (for example in the case of vehicle having a manual gearbox) a gear change is called for.

33 An electrically powered vehicle according to claim 32, wherein the amplitude and shape of the waveform are controlled by a logic circuit comparing the throttle setting (indicating the power being conveyed to the motor) with the motor speed and/or vehicle speed, thereby to simulate light and heavy load conditions on the motor.

34 An electrically powered vehicle according to claim 32 and claim 33 having a gearbox, wherein the frequency of the repetitive waveform is controlled to take into account the selected gear.

A noise simulator substantially as hereinbefore described with reference to any one or more of Figs 1 to 10 of the accompanying drawings.