|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. Creating a narrow beam is very challenging and the innovations that enable A-WASP to achieve this are patent protected. The key benefit is that it enables the user to broadcast to a chosen target without exposing themselves, their colleagues or bystanders to high sound levels. This means A-WASP is a highly discriminating tool.
Figure 1 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.
Fig. 2: % Sound Intensity By Angular Position
|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.
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.
Fig 3: The effect of the sound limiter and the sound level at range upon a target
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.
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.
|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 a handful of controls so the interface is very straightforward. It is designed to be used by one Officer and to be fully person-portable.
In addition, there is an on-board 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.
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.
Fig 4: LCD Targeting Display
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 there is an audio broadcast the previous 20 to 30s of camera footage is seamlessly included in this video file to provide context of use. Once the broadcast concludes 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). Further these records are useful for training.
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 the on-board safety limiter preventing the maximum average sound level exceeding 112dB LAeq at the target (user defined, 112dB LAeq has been selected by the UK Police).
112dB LAeq is less that 4% of the instantaneous maximum limit of 140dB(C) specified in all the above standards.
Noise exposure is based on an 8 hour working day and is cumulative. 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.
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 under EU(UK) law. This equates to 9 messages of 10s duration – well in excess of that required to get a target’s attention. 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 456 messages of 10 seconds duration – 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 with a given target should multiple exposures have taken place.
The following are granted patents protecting the A-WASP, further patents are pending for the rest of the world:
GB, Acoustic Apparatus and Operation, GB2511145
GB, Acoustic Apparatus and Operation, GB2520448
GB, Acoustic Apparatus and Operation, GB2520449
Singapore, Acoustic Apparatus and Operation, 11201508592X
China, Acoustic Apparatus and Operation, ZL2014800308735
Europe, Acoustic Apparatus and Operation, EP3004788
USA, Acoustic Apparatus and Operation, US9872100
Japan, Acoustic Apparatus and Operation, JP6438943
Australia, Acoustic Apparatus and Operation, AU2014272892
The following are registered design rights:
EU, Registered Community Design Right 002677237-0001, A-WASP
USA, US Design Right 29/525,865, Signalling Apparatus and Device
The following are granted trademarks:
EU, European Community Trademark, no. 012594321, A-WASP
USA, USPTO 4,769,716, A-WASP