NZ336109A

NZ336109A - Deterrent system for animals or intruders using steerable acoustic beam

Info

Publication number: NZ336109A
Application number: NZ33610999A
Authority: NZ
Inventors: John Haylock; Alexander Lang; Mark Poletti
Original assignee: Ind Res Ltd; Horticulture & Food Res Inst
Priority date: 1999-06-03
Filing date: 1999-06-03
Publication date: 2001-11-30
Also published as: AU4959900A; WO2001008478A1

Abstract

A pest or intruder deterrent system includes: a) a detection instrument to detect the presence and vicinity of a target in the form of an intruder or pest and b) a deterrent apparatus responsive to the detection instrument for directing a narrow focused sound beam in a range audible to the pest or intruder towards the vicinity of the intruder or pest with attenuated levels of sound propagated in other directions. The deterrent apparatus comprises a closely spaced, side by side array of loudspeakers to create the narrow focused beam by the technique of beamforming. Each of the loudspeakers has a respective horn with each of the horns being narrow enough to enable the apparatus to function as a beamformer.

Description

NEW ZEALAND PATENTS ACT, 1953 No: 336109 Date: 3 June 1999 COMPLETE SPECIFICATION DETERRENT SYSTEM AND ACOUSTIC APPARATUS tp T» O O o f~> _b - We, THE HORTICULTURE & FOOD RESEARCH INSTITUTE OF NEW ZEALAND LTD, a New Zealand company and Crown Research Institute (under the Crown Research Institutes Act 1992) of Corporate Office, Tennent Drive, Private Bag 11030 Palmerston North, New [£ Zealand, and INDUSTRIAL RESEARCH LIMITED, a New Zealand company of Gracefield •* -i v Road, Lower Hutt, New Zealand, do hereby declare the invention for which we pray that a patent rn may be granted to us, and the method by which it is to be performed, to be particularly described J?, in and by the following statement: - t K*l CD o h'r f-i"ir7r - - Field of the Invention The present invention relates to a deterrent system for unwanted intruders or pests. In particular, although not exclusively, the invention relates to a deterrent system for scaring 5 birds and small mammals from areas containing crops. The invention is also directed to control of pests or intruders through the use of highly focussed sound beams. An acoustic apparatus for producing highly focussed sound beams is also the subject of the present invention. Whilst the invention is described particularly in terms of controlling bird incursions into areas with crops, the invention is not so limited and may be adapted to 10 controlling other pests or intruders including humans from other controlled areas.

Background Art Since man first farmed, birds and small mammals have been responsible for serious losses 15 through their consumption and spoilage of human food. Much more recently we have entered a technological age in which they have come also to pose serious threats to our health, safety and enjoyment.

Deforestation and rapid changes in land use in the last 200 years and the indiscriminate 20 introduction of non-native species to previously isolated and therefore vulnerable ecosystems, have caused unprecedented levels of ecological damage. Whilst these changes have been responsible for catastrophic declines in, or extinctions of, the populations of some plants and animals they have also resulted in huge population growth for a handful of the more-adaptable species. Birds, in particular, because of their mobility 25 and intelligence, create special problems. Year by year these problems become more widespread and more severe.

Where wild bird populations impact on man and his activities, bird management has become of utmost importance and finding solutions to bird issues appear high on the 30 research agendas of many organisations. Most bird scarers and bird management techniques are, however, rather ineffective and even the most widely used, such as bangers, become less effective or even totally ineffective after just a few days as birds become habituated to them. Habituation is the waning of responsiveness to loud noises when birds learn that there is no danger.

Against this backdrop, a new pressure of social responsibility is gaining ground with rapid changes in public attitudes to solutions which involve chemical or noise pollution. There 3d is also a growing desire to live with nature rather than to fight it and this is putting very strong pressure on researchers to find more acceptable ways of managing wild populations.

High cost and the production of loud noise is increasingly restricting the use of the most effective means of control - a person with a gun. Mass poisonings create an ever stronger negative reaction as non-pest and even conservation species can also be destroyed.

An object of the present invention is to overcome or at least ameliorate some of the 10 abovementioned disadvantages. An alternative object is to provide the public with a useful choice.

Summary of the Invention In accordance with a first aspect of the present invention there is provided a pest or intruder deterrent system including: a detection instrument to detect the presence and vicinity of a target in the form of an intruder or pest; a deterrent apparatus responsive to the detection instrument for directing a narrow focused sound beam in a range audible to the pest or intruder towards the vicinity of the intruder or pest with attenuated levels of sound propagated in other directions, wherein the deterrent apparatus comprises a closely spaced, substantially side-by-side array of loudspeakers to create the narrow focussed beam by the technique of beamforming, each of the loudspeakers having a respective horn, each of the horns being narrow enough to enable the apparatus to function as a beamformer.

Preferable in order to keep the loudspeaker size to within practical limits, the frequency range of operation would be 1 to 10 kHz.

In accordance with a second aspect of the present invention there is provided a method of 30 deterring intruders or pests including: detecting the presence and vicinity of a target in the form of an intruder or pest; directing a narrow focused beam of sound within an audible frequency range of the intruder or pest towards the vicinity of the intruder or pest with attenuated levels of sound propagated in other directions, wherein the narrow focused sound beam is formed by a process of beamforming using a closely spaced, substantially 35 side-by-side array of loudspeakers, each of the loudspeakers having a respective horn, each of the horns being narrow enough to enable the apparatus to function as a beamformer. intellectual property office of n z. 1 8 OCT 2001 336 10 Preferable in order to keep the loudspeaker size to within practical limits, the frequency range of operation would be 1 to 10 kHz.

The degree of focussing which can be achieved will thus be greater than that achievable with a conventional loud speaker in the same frequency range. "Conventional loudspeaker" means a direct radiator loudspeaker or a driver loudspeaker coupled with a conventional horn to increase efficiency. It will be understood that a single conventional loudspeaker is able to achieve a degree of focusing which typically rises with frequency. In conventional direct radiator loudspeakers this is dependent on the frequency of the sound beam and radius of the loudspeaker. In a horn loudspeaker, the degree of focusing is dependent on the frequency of the sound beam, the area of the horn mouth and the particular shape of the inner part of the horn. As an example, consider a direct radiator loudspeaker in the form of a circular piston having a radius A within a large acoustic baffle. To achieve directionality of the propagated sound beam, the product kA must be larger than 1 where k=2Tif/c. It will be appreciated that, while the frequency range of operation is high, the loudspeaker dimensions would still be impractical to achieve high directionality in the frequency range of interest ie 1 to 10 kHz.

Preferably the method operates within a range whereby the whole range is normally audible to the intruder or pest. For example where the pest is a bird, the operational frequency range is preferably between 2 and 5 kHz. Further, the method may be such that the type of intruder or pest can be determined, with an adjustment of the frequency of the sound beam possible according to the type of intruder or pest determined.

Suitably, the horizontal distance between adjacent loudspeakers is less than X/2, where X is the wavelength at the highest frequency of operation. For the frequency range of 1 to 10 kHz, the loudspeakers will thus be closely packed. The loudspeaker drivers may be staggered to achieve the desired degree of close spacing in the sideways direction.

Preferably the source of the narrow focused beam is steerable either electronically or manually or through the use of a motorised platform. Where the beam is created by a process of beam forming, a linear variation of delays across the array is appropriate to achieve steering of the beam towards the intruder or pest.

The method set out above may be used to deter unwanted pests such as birds or other introduced animals. Alternatively, the method may intellectual property office of nz. 1 8 OCT 2001 truders of the 33 V human kind.

The invention according to the third and fourth embodiments may include a detection and discrimination instrument operable to detect the presence and vicinity of life forms and/or 5 moving objects within a control zone or within a predetermined range of the detection and discrimination instrument, the detection and discrimination instrument being operable to determine the presence of a target from any detected life forms or objects as well as to determine the target vicinity or direction from the detection and discrimination instrument.

Throughout the specification and claims, the term "target" is used to mean a predetermined unwanted intruder which the system has been set up to respond to and deter | from being within the control zone.

An equivalent method of providing a deterrent is also considered within the scope of the 15 invention.

The system may operate such that a deterrent is only directed towards the target when the target is within the control zone. In some embodiments of the invention, the detection and discrimination instrument may be able to detect the presence of targets outside the control 20 zone but within range of the detection and discrimination instrument thereby monitoring targets outside of the control zone ready for any intrusion into the zone.

The detection and discrimination instrument may determine the precise location of the detected life form and/or moving object but in many embodiments the general 25 whereabouts may be sufficient for effective operation of the system. The detection and deterrent instrument may be embodied in a moveable scanner, moveable to ensure adequate coverage of the control zone. A number of scanners may be employed to adequately protect the control zone.

The detection and discrimination instrument may be embodied in separate units for detection and discrimination respectively. In such an arrangement the detection unit might incorporate any conventional sensors such as infra-red or movement detectors or both. The discrimination unit, being responsive to the detection unit preferably incorporates image recognition technology to determine the presence of a target. In such a separate 35 arrangement the detection unit may be remote from the discrimination unit.

In another preferred form of the invention the detection and discrimination functions are intellectual property office of n.z. 1 fi nn 9nm intellectual property OFFICE of nz. 1 8 OCT 2001 C J RECEIVED embodied in a single unit. Such a unit may employ image recognition technology. The preferred detection and discrimination instrument employs video image analysis technology whereby pixel disturbance in a CCD screen is used to detect the presence of a life form and/or object, with image processing techniques used to verify whether the detected life form/object is a target.

More than one type of life form/moving object may be identified in the system as a target. The system may be variable to change the target(s). This may be achieved by a software change. Common targets include birds, although certain introduced species may be identified as targets with native species being not so identified. Other possible targets include humans, rabbits, possums and other pests.

The directional deterrent may be variable according to the circumstances. For example, the zone may be divided into an inner zone and an outer zone with a more severe deterrent delivered to targets entering the inner zone compared with the deterrent delivered to targets present in the outer zone. A more severe deterrent might be a louder sound or a sound which is more threatening to the target in question.

The directional sound beam may also be adjustable within certain ranges. For sound, such adjustments might include changes in pitch, volume, beam width and behavioural characteristics. Considering pitch, the choice of pitch would depend on the target. An appropriate pitch for birds would be in the range of 2 to 6 kHz which is within the range audible to humans. The noise level selected could be varied between different targets but preferably the noise level is not such that it would cause deafness to humans. An appropriate level could be 100 decibels at 100 metres from the source of the sound beam.

In order to further reduce annoyance and intrusion to neighbours of the control zone, the sounds used may be local or natural sounds. Sounds which emulate predators to the target animals are also desirable.

The deterrent may be directed at the target to allow for the moving trajectory of the target. On the other hand if the system is sufficiently responsive or the deterrent is sufficiently generalised, no specific adjustment for the moving trajectory may be required. As the deterrent is directed according to the detected position of the target, it is necessary for the deterrent apparatus to have adjustable aim. This may be achieved by physically moving the source of the deterrent. The source may move by pivoting or sliding and in particular a rotatable turntable may be provided for pivoting of the source. However other more * • < iimtellectual property office of nz. 1 8 OCT 2001 RECEIVED 't?d within" thu1 siupc jj sophisticated means of adjustment are considefed within llit siupc -of the present invention. In a preferred form of the invention electronic steering of a focused sound beam may be achieved.

The system may also provide for continued tracking of the target while in range of the detection and deterrent instrument and/or within the control zone. The tracking may be effected by systematic scanning within the range or the control zone. On the other hand tracking may be facilitated by calculating a probable position from a projected trajectory of the target and searching within the probable position. The system may accommodate a number of targets by responding with a directional deterrent in order of detection or ordered according to a convenient order on consideration of their relative positions.

In addition to the directional response provided to the target, the system may also provide responses to non-targets detected by the detection and discrimination instrument. For this purpose, the detection and discrimination instrument may also identify the detected life form/object which is not a target. To these non-targets, directional responses may also be delivered but other responses may also be provided. In a most preferred form of the invention, a response to humans within the control zone might be to warn them of the operation of the deterrent system including perhaps temporary disablement of the system.

Suitably, an interface is provided linking the detection and discrimination instrument with the apparatus providing the sound beam.

In accordance with a third aspect of the present invention (not claimed) there is provided a deterrent system for unwanted intruders including: a detection and discrimination instrument operable to detect the presence of life forms and/or moving objects within a control zone or a predetermined range of the detection and discrimination instrument and operable to determine whether any detected life forms or objects constitute a target; wherein the detection and discrimination means incorporates a tracking function such that on determination of the presence of a target, the detection and discrimination instrument is operable to track the presence of said target within the range or the control zone on at least one successive occasion; and the detection system further including deterrent apparatus responsive to the detection and discrimination instrument to automatically create a deterrent to the target on each occasion the target is detected within range or within the control zone.

An equivalent method of providing a deterrent is also considered within the scope of the present invention. intellectual profe&tyt' office of nzt' 1 8 OCT 2001 REG EBWED /O y, h 1 H ■i-y Preferably the invention according to the second aspect provides continued tracking with follow-up response while the target is within range or in the control zone, ceasing beyond 5 range or the control zone. This continued tracking is intended to activate the target animals' instinctive fear of being hunted. The system may operate to "watch" the target beyond the control zone but within range of the detection and discrimination instrument so that any incursion into the control zone will be promptly responded to.

The tracking may occur at regular time intervals. On the other hand, the tracking may be irregular, for example, at progressively reduced intervals for stubborn intruders. The \y tracking function may be achieved by systematic scanning of the control zone. On the other hand, a predicted trajectory of the moving target may be used to predict successive locations where the target may be detected.

In accordance with a fourth aspect of the present invention there is provided an acoustic apparatus including a plurality of loudspeakers in a substantially side-by-side array, each of the loudspeakers having a respective horn, the horns being sufficiently narrow to enable the apparatus to incorporate a steering function through the technique of beam forming 20 in the frequency range of 1 to 10 kHz using variable delays across the array.

The preferred frequency range is 2 to 5 kHz. In a most preferred form of the invention the range is 5 kHz which correlates to a wavelength of 68 mm. Thus in order for the , apparatus to function as a beam former at 5 kHz, the loudspeakers should preferably be 25 34 mm apart.

Given that 34 mm may be restrictive given the size of most commercial loudspeakers, the loudspeakers may be staggered vertically so as to meet the criteria of 34 mm apart.

The horns may have none or minimal flare in the sideways direction. Preferably there is a high degree of flare in the transverse ie the vertical direction. This flare may be exponential.

This invention may also be said broadly to consist in the parts, elements and features 35 referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such lcnown equivalents are deemed to be incorporated herein as if individually set forth.

The invention consists in the foregoing and also envisages constructions of which the following gives examples only. intellectual property office of nz. 1 8 OCT 2001 RECEIVED Brief Description of the Drawings In order that the invention may be more fully understood, one embodiment will now be described by was of example with reference to the drawings in which: Figure 1 is a schematic view of the deterrent system in accordance with a preferred embodiment of the present invention; Figure 2 is a schematic view of a beamforming array for use in conjunction with the 10 deterrent system illustrated in Figure 1; Figure 3 is a schematic view of the loudspeaker horn arrangement adapted for use in the deterrent system illustrated in Figure 1; Figure 4 is a circuit diagram for a divider circuit for each of the loudspeaker drivers; and Figure 5 shows a typical polar response using beamforming techniques in accordance with the present invention.

Preferred Embodiment Figure 1 illustrates schematically the operation of a deterrent system 10 used for deterring pests such as birds 11 from entering a control zone 12. The main components of the system include a detection and discrimination instrument C used to detect the presence of 25 birds 11 within the control zone 12 and to determine whether such birds constitute a target for the deterrent system 10. The detection and discrimination instrument C is preferably in the form of an image processor such as a CCD camera. For the purposes of the present example, the system 10 is programmed to deter all types of birds entering the control zone 12. The second main component of the system 10 includes directional deterrent apparatus 30 B. The directional deterrent apparatus B is linked to the detection and discrimination instrument C via signals processor A. The processor A contains means for storing audio waveforms, reading the waveforms and sending them to the directional deterrent instrument B. By means of the processor A, the directional deterrent apparatus B is responsive to the detection and identification of a target by detection and discrimination 35 instrument C. In other words, when the detection and discrimination instrument C locates a target, a signal is sent to the processor A which in turn sends a signal to the directional deterrent apparatus B to send a deterrent to the birds 11. In addition, the detection and discrimination instrument C may also send a signal representative of the direction or vicinity of the detected birds 11. The processor A in turn sends a signal to the directional deterrent apparatus B so that the deterrent will be directed towards the birds 11 as illustrated.

The deterrent is preferably a narrow focused sound beam with attenuated levels of sound propagated in the other directions. In this manner, neighbours 15 to the control zone 12 will receive minimal noise leakage from the control zone 12.

Furthermore, the system may be designed to continually track the birds while in the control zone and provide repeated responses to a particular bird while it remains in the control zone. In this manner, the system attempts to bring out the birds' fear of being hunted to thereby reduce the likelihood of habituation to the deterrent.

In order to achieve a narrow focused beam, the directional deterrent apparatus B incorporates a loudspeaker array which is designed to provide a narrow beam of sound which can be steered in a desired direction by beamforming techniques. The theory of beam steering will be understood to those skilled in the field. To summarise: a linear array of 20 loudspeakers, each receiving the same signal, will produce a narrow beam of sound on axis with relatively low radiation of sound in off-axis directions. By applying a linear variation of delays across the array, the beam can be 'swung' to a direction different than on-axis. The radiation of sound at angles away from the main beam (sidelobes) may be further reduced by reducing the amplitude of signals sent to the speaker elements at the 25 ends of the array.

Array design Figure 2 shows the general principle of a beamforming array. A signal s(t) is input to N 30 delay lines, with delay times to . The outputs of each delay line are scaled in amplitude by weighting coefficients to aN, and the weighted delayed signals applied to power amplifiers A, to AN and loudspeakers L, to Ln. If the delay lines are arranged to have a linear increase in delay across the array, then the signal leaving the Nth loudspeaker will be broadcast at a later time than that of the (N-l)th loudspeaker, which 35 will be broadcast later than the (N-2)th loudspeaker, and so on. If the loudspeakers are close enough together, the pressure signals they generate combine to form a single wavefront which propagates in a direction t degrees from the line perpendicular to the array. The required delays are given mathematically by T" =~sin(^ (1) where d is the spacing between the loudspeakers and c is the speed of sound in air. The direction of propagation may thus be varied by altering the delay variation between the loudspeakers.

Image Processor The image processor preferably consists of a CCD camera which focuses the image in its field of view onto a CCD optical sensor. The CCD sensor samples the image spatially in a two dimensional array of "pixels" by converting the light falling on each pixel into an electrical charge. The charges are read out of the sensor array fR times every second, 15 where fR is the frame rate, sampled by an analog to digital convertor, and the samples representing the image in each frame are stored in digital memory.

The camera contains one or more image processor devices which process successive images to determine whether a target exists in the field of view. Such image processing 20 typically commences by taking the difference between successive frames in order to eliminate non-moving elements of the image such as those due to background objects. The processors then further processes successive frame differences in order to detect moving objects, using image processing techniques which will be known to those skilled in the art. For example, spatial filtering may be used to enhance high frequency 25 components to allow the detection of edges, or to eliminate noise components in the image.

The image processors also run a prediction algorithm on any detected targets in order to estimate their angular velocity and direction. The target information is then transmitted 30 from the CCD camera to the processor A (figure 1) - typically via a serial digital format -which initiates the directional deterrent apparatus B to deliver an audible deterrent response to the target.

Description of Non-steering Loudspeaker Array Prototype As an example of a beamforming loudspeaker array, a prototype system was constructed in which electronic steering was not implemented. The array therefore only radiates sound in a focused beam directly to the front of the array (on-axis). In this simple case no delay elements are required for the array, and the loudspeaker drivers may in principle all be driven from a single amplifier. In practice, four amplifiers were used, each driving four loudspeakers. The weights an were implemented as passive attenuators using 5 capacitors, as will be described below.

The two requirements of the array are 1) It should provide the highest possible sound pressure levels over the required frequency 10 range of 1 to 5 kHz at reasonable battery consumption. This requirement is best satisfied using a horn loudspeaker. 2) It should produce a narrow beam of sound with minimal radiation of sound in unwanted directions over the required frequency range.

The second requirement specifies the maximum size of the loudspeaker elements in the array. For beam steering using an array of loudspeakers, the loudspeakers must be spaced closer than X/2 where X-df is the wavelength associated with the radiated frequency /, and c is the speed of sound. The maximum frequency at which beamforming may occur 20 without the generation of large unwanted sidelobes (aliasing lobes) is f max ~" « , 2d (2) The required array element spacings for a number of maximum frequencies is thus d f max < 170mm 1kHz < 85.0mm 2kHz < 42.5mm 4kHz < 21.3mm 8kHz Table 1: Transducer spacing for beamforming at maximum frequency fr The spacing requirement is too restrictive to allow a horn design if directional control is required in both vertical and horizontal planes. However, in the application here, the sound need only be steered in one direction eg horizontally with a fixed vertical radiation pattern. A 'one dimensional' horn 20 may therefore be built which flares vertically but remains narrow in the horizontal direction. See Figure 3 for a schematic representation.

Loudspeaker Element Design Driver Selection The Motorola range of piezo horn drivers are commonly used in public address loudspeakers, and are relatively cheap (around NZ$20.00). The Motorola Powerline KSN1142A driver has a standard thread that allows the fitting of a separate horn. The driver has the following specifications: Frequency response 1.8 kHz to 30 kHz Average sensitivity 92dB @ lm/2.83v (2.83 volts = 1 watt into 8 ohms) Maximum Power 400Watts Maximum Temperature 80 degrees C Typical Impedance Appears as a 0.3(iF capacitor The frequency response is measured with the driver fitted to a 2 by 6 inch Motorola exponential horn. It is therefore likely that the horn designed here will have a similar response; in particular it will begin to roll off below 2 kHz.

The Powerline drivers contain the parallel combination of a miniature light bulb and a positive temperature coefficient resistor. These two devices protect the driver from high temperatures caused by amplifier clipping or high levels of high frequency energy (where the capacitive load impedance is small).

The driver 22 has an outside diameter of 64 mm. This size means that the maximum frequency of beamforming would be 2.6 kHz. This is too low to allow beamforming over the frequency range of bird signals (1 to 5 kHz). However, the driver output duct has a diameter of about 32mm. A staggered design illustrated in Figure 3 was therefore developed. The spacing of the adjacent drivers 22 when measured between vertical lines extending through the drivers 22 is only 32 mm in this staggered array, thus producing a maximum beamforming frequency of 5.3 kHz.

The driver 22 has an internal dimension at its output of 22.23mm. In order to prevent the reflection of energy back into the driver 22 from a change in cross sectional area, any horn connected to the driver 22 should have the same internal diameter.

Horn Design An exponential horn 20 has a cross sectional area as a function of distance, x, from the driver of SM = Sre~ (3) where m is the flare constant (see L. Beranek, Acoustics, 1993 Edition, published by the Acoustical Society of America) and ST is the area of the throat (entrance) of the horn. In the case where the horn has a fixed width, the height, h, of the horn varies in the same 10 manner h(x) = hTemx (4) where hT is the height at the throat. An analysis of wave propagation in horns shows that they allow the transmission of sound waves with little attenuation above a cutoff 15 frequency, given by (see the reference mentioned above): f _ mc (5) c An Since the horn designed here has parallel vertical sides, cross modes will occur when the wavelength is greater than twice the internal duct width. The first cross mode frequency 20 is ^ fcmodc ~ ^ (6) where w is the internal width. Since the sound radiation characteristics of the horn becomes more complicated above the first cross mode frequency, it is desirable that this 25 frequency be above the frequency range of interest.

A prototype horn 20 was designed and constructed from 4mm PVC, by heat forming the upper and lower exponential flares to a wooden former and gluing PVC sheet to each side. An adaptor was machined from solid PVC which mated the circular opening of the 30 Motorola driver to the rectangular throat of the horn 20, and which had an internal thread matched to the driver thread.

The horn 20 had the following characteristics: Length L Internal width w Flare constant 240mm 23mm .85 Height at opening 300mm Cutoff frequency 293 Hz First cross mode 7.4 kHz The cutoff frequency is well below the operating frequency range of the device, and the first cross mode above the upper frequency range of 5 kHz, as required.

Array Implementation In order to reduce sidelobes, a window was applied to the array. A Kaiser window with a Kaiser parameter of 1.5 was used. This produced a reasonable reduction in sidelobes, without reducing the main beam amplitude significantly.

Since the Motorola drivers appear as capacitors, the window weights were implemented 15 in practice as capacitive dividers. The circuit diagram of a single divider circuit is shown in Figure 4. A resistor is also included in order to limit the high frequency impedance and reduce the risk of amplifier instability.

The Laplace transform of the voltage across the loudspeaker, V0(s), is given by eSc^lc,*™ <7) where (8) C = ClCl p Cj + c. is the series capacitance of both capacitors. The network thus implements an attenuator with gain C/tCj+Q) at low frequencies, and a high frequency rolloff frequency of fL=l/(2TtRCp). R was chosen as 33 ohms. With C ^0.3(xF the normalised Kaiser window coefficients, capacitor values and roll-off frequencies are Speaker Kaiser window C2(^IF) Cp(jJ-F) fL(kHz) Number Coefficient 1,16 .608 0.47 0.183 26.3 2,15 .697 0.68 0.208 23.2 3,14 .777 1.00 0.231 .9 4,13 .848 1.65 0.254 19.0 ,12 .907 3.00 0.273 17.7 6,11 .953 6.03 0.286 16.9 7,10 .984 18.60 0.295 16.3 8,9 1 oo 0.300 16.1 Table 2: Kaiser window coefficients, capacitor values and cutoff frequencies.

Amplifier Specification Since the horn array is to be used outdoors and run from a car battery (at least in initial field testing), an amplifier is required that runs from 12 volts. For this reason a car audio 15 amplifier was chosen. The amplifier is a Rockford Fosgate Punch 400.4. The amplifier has four channels, and the following specifications of relevance: Continuous power rating into 4 ohms at 13.8 volts 50 Watts Frequency response 20Hz - 20 kHz Input sensitivity 150 mV to 3V Input impedance 20 kilohms The amplifier contains an internal dc-dc convertor which allows it to produce an output 25 swing of around 25 volts peak max. This allows the amplifier to produce greater power output than standard car amplifier chips such as the Philips TDA series, which offer bridge outputs and an effective peak voltage of 12 volts.

The input sensitivity of each amplifier was adjusted to one volt, so that a one volt peak 30 input signal connected to each input produced an output from the corresponding amplifier of just below clipping.

Polar Response Figure 5 shows a typical polar response that may be obtained using beamforming techniques. A sixteen loudspeaker array is used, and the direction of propagation is thirty degrees. The loudspeakers were spaced at 0.45A to ensure a single wavefront without aliasing.

The typical polar response of a single conventional loudspeaker is shown as the dash-5 dotted line. The response has a broad peak at zero degrees, with a null at 180 degrees (not shown). The typical polar response produced for a "N30 degrees and all weightings an=l is shown as the dashed line. The response has a peak at 30 degrees, and drops off rapidly at other angles, where a number of sidelobes occur periodically with angle.

The effect of applying windowing to the array is shown as the solid line. The applied window was a Kaiser window with Kaiser parameter 1.5. The sidelobes are reduced by about 5 dB. There is also a reduction in the main peak of about 1.5 dB, so the peak to sidelobe ratio is improved by around 3.5 dB.

Advantages It is believed that the deterrent system in accordance with the present invention offers the following advantages over existing bird control technologies: Firstly, the new technology will be activated only when the control zone is invaded. Birds will be scared as a result of being noticed and 'hunted' by the noise rather than simply experiencing a 'fear of the unfamiliar'. Target species are thus much less likely to become habituated to this system than they are to conventional scarers.

Secondly, the system will have much less environmental impact than conventional gas gun bangers. Although the new deterrent is based on scaring birds with loud noise (c. 100 dB at 100m), the new speaker array technology delivers a defined beam of sound with very little sound 'leakage' to uncontrolled airspace compared with conventional bangers. Despite restrictions by municipal councils on the hours of use of conventional bangers 30 there are growing numbers of complaints over their usage.

Claims

WHAT WE CLAIM IS: intellectual property office of nz. 1 8 OCT 2001 RECEIVED

1. A pest or intruder deterrent system including: a detection instrument to detect the presence and vicinity of a target in the form of an intruder or pest; a deterrent apparatus responsive to the detection instrument for directing a narrow focused sound beam in a range audible to the pest or intruder towards the vicinity of the intruder or pest with attenuated levels of sound propagated in other directions, wherein the deterrent apparatus comprises a closely spaced, substantially side-by-side array of loudspeakers to create the narrow focussed beam by the technique of beamforming, each of the loudspeakers having a respective horn, each of the horns being narrow enough to enable the apparatus to function as a beamformer.

2. The system as claimed in claim 1 wherein the deterrent apparatus is operable to direct the focussed sound beam in a frequency range of 1 to 10 kHz.

3. The system as claimed in claim 1 wherein the deterrent apparatus is operable to direct the focussed sound beam in a frequency range 2 to 5 kHz.

4. The system as claimed in any one of claims 1 to 3 wherein the detection instrument is operable to determine the type of intruder or pest with the system being responsive to the determined type to tailor the frequency of the sound beam according to the type of intruder or pest.

5. The system as claimed in any one of claims 1 to 4 wherein each of the loudspeakers have respective horns which are flared in the upright direction with a narrow dimension in the sideways direction to enable the close sideways spacing of the loudspeakers.

6. The system as claimed in any one of claims 1 to 5 wherein the loudspeaker drivers are staggered to achieve the desired degree of close spacing in the sideways direction.

7. The system as claimed in any one of claims 1 to 6 wherein the deterrent apparatus incorporates a steering facility to electronically steer the narrow focused beam by creating a linear variation of delays across the array.

8. The deterrent system as claimed in any one of claims 1 to 7 wherein the detection ^\ /rs intellectual property vyz ~j r) " '/) office of n.z. 1 8 OCT 2001 -20- ^ECEIVEO instrument is programmed to detect any of the following,—erthep-stfigutely-oc-combination: birds, possums, rabbits, humans. in

9. The deterrent system as claimed in any one of claims 1 to 8 wherein: the detection instrument is operable to detect the presence and vicinity of life forms and/or moving objects within a control zone or within a predetermined range of the detection instrument, the detection instrument being operable to determine the presence of a target from any detected life forms or objects.

10. The deterrent system as claimed in claim 9 wherein the detection instrument is operable to detect the presence of targets outside the control zone but within range of the detection instrument, with the deterrent apparatus being limited to direct a deterrent towards a target which is within the confines of the control zone.

11. The deterrent system as claimed in claim 9 or claim 10 wherein the detection instrument includes one or more moveable scanners.

12. The deterrent system as claimed in any one of the preceding claims wherein the detection instrument employs video image analysis technology whereby pixel disturbance in a CCD screen is used to detect the presence of a life form and/or object, with image processing techniques used to verify whether the detected life form/object is a target.

13. The deterrent system as claimed in any one of the preceding claims wherein the detection instrument is adapted to identify more than one type of life form/moving object as a target.

14. The deterrent system as claimed in any one of the preceding claims wherein the detection instrument is variable to change the target(s).

15. The deterrent system as claimed in any one of the preceding claims wherein the noise level of the directional sound beam is not such that it would cause deafness to humans.

16. The deterrent system as claimed in any one of the preceding claims wherein the sound beam incorporates local or natural sounds.

17. The deterrent system as claimed in any one of the preceding claims wherein the 10 % 15 20 •i 30 -21 sound beam incorporates sounds which emulate predators to the targets J. intellectual property office of n.z. 1 8 OCT 2001 EIVED

18. The deterrent system as claimed in any one of the preceding claims wherein the system is adapted to accommodate the moving trajectory of the target(s).

19. The deterrent system as claimed in any one of the preceding claims wherein the detection instrument incorporates a tracking function to continuously track the target while in range of the detection instrument and/or within the control zone.

20. The deterrent system as claimed in claim 19 wherein the tracking function is effected by systematic scanning within the range or the control zone.

21. The deterrent system as claimed in claim 19 wherein the tracking function is effected by calculating a probable position from a projected trajectory of the target and searching within the probable position.

22. The deterrent system as claimed in any one of the preceding claims wherein the system accommodates multiple targets by responding with the focussed sound beam in order of detection or ordered according to a convenient order on consideration of their relative positions.

23. The deterrent system as claimed in any one of the preceding claims wherein the system identifies any one of the following singularly or in combination as target(s): birds, rabbits, possums and humans.

24. A method of deterring intruders or pests including: detecting the presence and vicinity of a target in the form of an intruder or pest; directing a narrow focused beam of sound within an audible frequency range of the intruder or pest towards the vicinity of the intruder or pest with attenuated levels of sound propagated in other directions, wherein the narrow focused sound beam is formed by a process of beamforming using a closely spaced, substantially side-by-side array of loudspeakers, each of the loudspeakers having a respective horn, each of the horns being narrow enough to enable the apparatus to function as a beamformer.

25. The method as claimed in claim 24 wherein the frequency range of the narrow focussed beam is 1 to 10 kHz. 10 % 15 20 •• 30 ^ V Kv, > s* J in i '/ -' 1 !' 1 \y u \ / "V , 22-

26. The method as claimed in claim 24 wherein the frequency range of the narrow focused beam is 2 to 5 kHz.

27. The method as claimed in any one of claims 24 to 26 further including determining the type of intruder or pest and tailoring the frequency of the sound beam according to the type of intruder or pest.

28. The method as claimed in any one of claims 24 to 27 wherein each of the loudspeakers have respective horns which are flared in the upright direction with a narrow dimension in the sideways direction to enable close sideways spacing of the loudspeakers.

29. The method as claimed in any one of claims 24 to 28 wherein the loudspeaker drivers are staggered to achieve the desired degree of close spacing in the sideways direction.

30. The method as claimed in any one of claims 24 to 29 further including electronically steering the narrow focused beam by creating a linear variation of delays across the array.

31. The method when used to deter any of the following, either singularly or in combination: birds, possums, rabbits, humans.

32. The method as claimed in any one of claims 24 to 31 wherein: the step of detecting a target involves operating a detection and discrimination instrument to detect the presence and vicinity of life forms and/or moving objects within a control zone or within a predetermined range of the detection and discrimination instrument, and determining the presence of a target from any detected life forms or objects as well as determining the target vicinity or direction from the detection and discrimination instrument

33. The method as claimed in claim 32 wherein the detection and discrimination \ instrument employs video image analysis technology whereby pixel disturbance in a CCD screen is used to detect the presence of a life form and/or object, with image processing techniques used to verify whether the detected life form/object is a target.

34. The method as claimed in any one of claims 24 to 33 wherein the pitch of the sound beam depends on the target. intellectual property office of n.z. 1 8 OCT 2001 c* ^ a «a ■*. 1 8 OCT 2001 ksseived

35. The method as claimed in any one of claims 24 to 34 wherein the sound beam incorporates local or natural sounds.

36. The method as claimed in any one of claims 24 to 35 wherein the sound beam incorporates sounds which emulate predators to the target(s).

37. The method as claimed in claim 32 including programming the detection and discrimination instrument to continuously track the target while in range of the detection and discrimination instrument and/or within the control zone.

38. The method as claimed in claim 37 wherein the tracking is effected by calculating a probable position from a projected trajectory of the target and searching within the probable position.

39. An acoustic apparatus including a plurality of loudspeakers in a substantially side-by-side array, each of the loudspeakers having a respective horn, the horns being sufficiently narrow to enable the apparatus to incorporate a steering function through the technique of beam forming in the frequency range of 1 to 10 kHz using variable delays across the array.

40. The acoustic apparatus as claimed in claim 39 wherein the arrangement and configuration of the horns is such that the apparatus is operable as a beam former in the frequency range of 2 to 5 kHz.

41. The acoustic apparatus as claimed in claim 39 wherein the loudspeakers are staggered vertically to be approximately 34 mm apart in the sideways direction.

42. The acoustic apparatus as claimed in any one of claims 39 to 41 wherein the horns have no flare in the sideways direction.

43. The acoustic apparatus as claimed in any one of claims 39 to 42 wherein the horns have a flare in the upright direction which is exponential.

44. A deterrent system for unwanted intruders substantially as hereinbefore described with reference to the accompanying figures.

45. A method of deterring unwanted intruders substantially as hereinbefore described -24- with reference to the accompanying figures.

46. An acoustic apparatus substantially as hereinbefore described with reference to the accompanying figures. tVe. V-\orV\ool4-uV-e cxv-oV Food Of tOe-vjO cws cxtng! I ^.©soa-rci^ I—WM \~c==xd Ly 11 L^nis n J r/nruC Kf -29-ABSTRACT A deterrent system (10) and method for unwanted intruders (11) includes a detection and discrimination instrument (C) and a directional deterrent apparatus (B). The detection and discrimination instrument (C) is operable to detect the presence and vicinity of life forms and/or moving objects withm a control zone (12) or within a predetermined range of the detection and discrimination instrument (C). The detection and discrimination instrument (C) is also operable to determine the presence of a target (11) from any detected life forms or objects as well as to determine the target vicinity or direction from the detection and discrimination instrument (C). The deterrent apparatus (B) is responsive to the detection of a target by the detection and discrimination instrument (C) to automatically create a deterrent on detection. The directional deterrent apparatus (B) may have a steering facility to direct the deterrent in the detected vicinity of the target. The system may also incorporate a tracking function to track the target (11) while it remains within the control zone (12) or within range of the detection and discrimination instrument (C). The deterrent apparatus (B) may create a narrow focused sound beam with attenuated levels of sound propagated in other directions. Specifically, the deterrent apparatus (B) may comprise a plurality of loudspeakers (22) arranged in a side-by-side array, each loudspeaker having a respective horn (20) which is sufficiently narrow to enable beamforming m the frequency range of 1 to 10 kHz.