Innovation

A-WASP® incorporates many innovations and this page details the principal features.

Directivity

The core functionality of the A-WASP® is to create a narrow beam of sound that can be used to selectively target an individual or individuals over 10s of metres. The key concept is that it is designed not to send verbal messages but to project a specific waveform at select frequencies – “intense-sound-mode”. By tailoring the design to this waveform it is possibly to achieve an astonishingly directional acoustic output. This acoustic output acts as a clear warning to ranges beyond 120m, and an exponentially increasing deterrent from 60m to point blank range.

Fig. 1 Polar plot of the output of the A-WaSP™ at 4kHz

Fig. 1 Polar plot of the output of the A-WASP® at 4kHz

Figure 1 below shows a polar plot on a decibel scale at a key output frequency of 4kHz. This shows an extremely narrow sound cone with a core beam of only +/-7.5 degrees (-3dB) and a very rapid rate of drop off at the edges. It also demonstrates minimal off-axis intensity outside the core beam.

The effect is extremely stark. Outside the main beam the acoustic signal is audible but the intensity is relatively low until you move into the main beam, at which point the onset is extremely rapid.

Figure 2 shows an alternative representation of the device output directionality, in this case as function of relative intensity by angular position. As can be seen the intensity experienced by any bystander is extremely low by comparison with the target and those parallel or behind the device experience less than 1% of that experienced by the target at a same range.

This very high level of directionality has to be experienced to be really appreciated – all those members of Police Forces and Government Agencies who have experienced it, so far, are in agreement on this point.

Fig. 2: % Sound Intensity By Angular Position

Fig. 2: % Sound Intensity By Angular Position

The two key benefits of this directionality are (i) that users can accurately and selectively target individuals or groups over 10s of metres of range and (ii) that bystanders and the user experience much lower sound levels – maximising the device selectivity and also its safety by minimising inadvertent exposure to non-targets. For example, the user can talk at a comfortable level to those nearby even when the device they are holding is running at full power.

Safety Limiter

The unit is specifically designed to avoid any judgement issues on the part of the user. The user aims the device and presses the trigger button. At which point a built in laser range finder instantly measures the distance to the target. A pre-determined maximum sound level is programmed into the device (the UK Police Service have specified 112dB LAeq as the maximum level but this is up to the end-user specifying the system parameters). If the target is within the corresponding range, the device will be automatically limited so that the sound level will not exceed that maximum level, if the target is beyond that range the level will be below that anyway. This is a safety limiting function.

Figure 3: The effect of the sound limiter and the sound level at range upon a target

The blue line in Figure 3 shows the sound level without the safety limiter and the red line with. As can be seen any distance below 13m and the safety limiter will limit the sound level at the target to 112dB(A).

This means that the user has minimal judgement issues over use. They simply aim, press, and the device controls the sound exposure at target to pre-set levels – even at point blank range.

User Interface

The device is designed to be worn on a shoulder strap by a Police Officer and to be highly intuitive to use. It is configured as a “sound gun” with a handle and a trigger and so is very easy to understand. There are only four buttons – the trigger and a safety switch on the grip; and buttons for pre-recorded verbal messages and to activate the laser range finder on the top – so the interface is very straightforward. It is designed to be used by one Officer and to be fully man-portable.

In addition, there is a sunlight-readable LCD display which displays the live feed from a coaxial camera along with overlaid user information. A representation is shown in figure 4.

Figure 4: LCD Targeting Display

The LCD displays cross-hairs which enable easy targeting for the user. In addition there is a time and date stamp along with a battery life indicator. The information at the top corner is the distance measured by the on-board laser range finder, plus the safe daily exposure time calculated for the sound level at that distance.

Integral Evidence Logging

A primary function of the device is to record in detail its use: before, during and after its deployment.

The unit incorporates a high quality video camera which provides live feed to the user via an LCD. Whenever the device is activated the device records the feed from the camera as an MPEG4 video file which is stored on an internal removable USB flash drive. In addition, a video buffer function is employed such that when the trigger is pressed the previous 20 to 30s of camera footage is seamlessly included in this video file to provide context of use. Once the trigger is released the video continues to save for a further 60s to give yet further context.

In parallel, the unit also incorporates GPS which, combined with the range finder and on board exposure calculations, saves a complete record of use for each trigger press as a .csv text file to the flash drive.

Such an exhaustive integral audit trail provides the user with very strong evidence to refute any allegations of misuse of the device – discouraging expensive legal challenges from members of the public. It also discourages misuse of the unit because the operator knows that all uses will be comprehensively recorded and that there will be suspicion should those records be found to be missing.

Compliance with Health & Safety Regulations

A key design element of the A-WASP® is that it is works within existing Health & Safety legislation i.e. if it is used correctly it will not expose the target, user or bystanders to hazardous sound exposure levels. To the author’s knowledge this is the only technology in this field which works within an existing legal framework – all other devices constitute a use of Force.

This means that use of the device is highly defensible in a legal context. The target is only exposed to sound levels that are already defined as legally acceptable.

The relevant legislation is for the control of noise at work. UK legislation is derived from EU legislation which is in turn guided by the ISO standard 1999:1910. US legislation both OSHA and NIOSH is also derived from the ISO standard – although OSHA is more lenient than NIOSH.

Compliance is accomplished by limiting the maximum average output to 134dB(A) at 1m, which is a quarter of the power level of the instantaneous limit of 140dB(C) specified in all the above standards. Noise exposure is based on an 8 hour working day and is cumulative. Thus under EU(UK) law a person may be exposed to a maximum average sound level over an 8 hour period of 87dB LAeq – but that may come in shorter bursts at higher sound levels as long as this average is not exceeded.

Figure 5: The permissible limits for sound exposure in an 8-hour period by sound pressure level

Figure 5: The permissible limits for sound exposure in an 8-hour period by sound pressure level

Due to the high directionality of the device and the safety limiter it is possible to ensure that target, user and bystanders are kept within these limits. For example at the safety limit of 112dB LAeq a target may be exposed to 91s daily at this level. This equates to 30 bursts of 3s – well in excess of that required to persuade a target to desist. If the target continues after even 5 bursts then the Officer should be considering moving up the Force Escalation spectrum. Also, in an open environment, the user and adjacent bystanders would typically experience around 95dB LAeq at maximum output – equating to a daily dosage limit of 1 hour 16 minutes – or >1500 bursts of 3 seconds – plenty of headroom; and avoiding the inconvenience of hearing protection.

To aid decision making on dosage the range taken with each trigger press shows the max daily exposure permissible by target at that range on the LCD screen (see figure 4) – this helps the user readily assess at what point to stop using the device against a given target should multiple exposures have taken place.

Patents

The inventions incorporated within the A-WASP® technology are patent granted in the UK and patent pending in the Rest of the World.

The A-WASP® is protected by a Registered European Community Design Right and a United States Design Patent.