TECHNICAL FIELD

This disclosure relates to a noise dosimeter system, a noise dosimeter device, a computing device and a method of monitoring noise exposure. BACKGROUND

A person's exposure to sound and noise may exceed recommended safety exposure limits. This can lead to negative impacts on a person's hearing. For instance, a person may experience symptoms such as deafness and tinnitus. This can be a particular problem for people working in noisy factory environments and other loud places such as heavy construction sites or loud entertainment venues.

There exists a need to be able to more accurately monitor the sound/noise levels to which a person is exposed and the circumstances corresponding with the sound/noise levels. In addition, it would be desirable to be able to generate data to enable people to make pre-emptive decisions that may help to lower their exposure to noise. SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. According to one aspect of the invention there is provided a noise dosimeter system comprising: an audio input device for receiving audio; and a noise level module arranged to determine a noise level based on the received audio; wherein the audio input device is associated with a positioning module arranged to: determine a position of the audio input device corresponding with the determined noise level ; and arranged to associate the position of the audio input device with the corresponding noise level.

According to another aspect of the invention there is provided a noise dosimeter device comprising: an audio input device for receiving audio; and a noise level module arranged to determine a noise level based on the received audio; and a communication interface arranged to transmit the noise level to a positioning module arranged to: determine a position of the audio input device corresponding with the determined noise level; and arranged to associate the position of the audio input device with the corresponding noise level. According to another aspect of the invention there is provided a computing device comprising: a communication interface arranged to receive a noise level based on audio received at an audio input device; and a positioning module arranged to: determine a position of the audio input device corresponding with the determined noise level; and arranged to associate the position of the audio input device with the corresponding noise level.

According to another aspect of the invention there is provided a method of monitoring noise exposure comprising: receiving audio at an audio input device; determining a noise level based on the received audio; determining a position of the audio input device corresponding with the determined noise level; and associating the position of the audio input device with the corresponding noise level.

According to another aspect of the invention there is provided a dosimeter system comprising: an input device for receiving an environmental parameter other than audio; and an environmental parameter level module arranged to determine an environmental parameter level based on the received environmental parameter; wherein the input device is associated with a positioning module arranged to: determine a position of the input device corresponding with the determined environmental parameter level; and arranged to associate the position of the input device with the corresponding environmental parameter level.

According to another aspect of the invention there is provided a method of monitoring exposure to an environmental parameter other than noise comprising: receiving an environmental parameter at an input device; determining an environmental parameter level based on the received environmental parameter; determining a position of the input device corresponding with the determined environmental parameter level; and associating the position of the input device with the corresponding environmental parameter level.

According to another aspect of the invention there is provided a computer program comprising code portions which when loaded and run on a computer cause the computer to execute a method as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described, by way of example, with reference to the following drawings, in which: Figure 1 schematically shows the basic general architecture of a noise dosimeter system ;

Figure 2 shows a more detailed illustration of the basic general architecture of a noise dosimeter system ; Figure 3 shows a flow chart illustrating a method of using the noise dosimeter system;

Figure 4 shows an example of a user interface display;

Figure 5 shows a schematic illustration of a server in the system; and

Figure 6 illustrates a look up table that can be used to determine a user's allowable exposure to noise in percentage terms.

DETAILED DESCRIPTION

Referring to Figure 1 , there is a noise dosimeter system 1 comprising a plurality of headsets 3, each worn by a different user 4. Each user 4 is equipped with a computing device 5. In this example, the computing devices 5 are smartphones. However, it will be appreciated that any other suitable computing device 5 may be used instead of a smartphone.

Each computing device 5 is connected to a server 7 via the Internet 2. In this example, the computing devices 5 and the server 7 communicate with one another via the Internet 2. However, any other suitable wired and/or wireless network may be used.

In the noise dosimeter system 1 each one of the headsets 3 receives audio from its surrounding environment and a noise level is determined. Each noise level determined is associated with a position at which the audio was received, from which the noise level was determined. Thus, each position is associated with a corresponding noise level. Typically, the noise level will indicate the amplitude of the audio received. For instance, the noise level may be the peak amplitude of the audio in decibels (dB) received at a particular time or an equivalent continuous value over a specified period of time in decibels (dB).

The system 1 is able to generate an indication of the noise level to which a person has been exposed along with positional information associated with the noise level. Thus, the person can associate a particular location with a particular noise level. For example, it may be possible to determine that a particular location within a factory is associated with a particularly high noise level. Therefore, the person can decide to avoid that location in order to limit their exposure to potentially harmful noise levels.

Preferably, the headset 3 is head-mounted or ear-mounted and is sound reducing, for example, comprising ear defenders for reducing noise level exposure. Thus, users' exposure to noise may be reduced. The system 1 may store a plurality of the positions each in association with a corresponding noise level. Thus, it is possible to generate information describing locations with associated noise levels. This helps to build a more complete indication of the noise levels throughout an environment. This can help someone to make better decisions about which areas to avoid, in order to limit their exposure to potentially harmful noise levels.

The information generated can be used to output map data which can be presented to a user in combination with a map of an environment in which the audio was received. This may present, to the user, at least some of the positions each in association with their corresponding noise level. This map may be regarded as a noise intensity map. The map can also present at least one high noise level area indicative of a position associated with a noise level above a high noise level threshold. Furthermore, the map may present at least one boundary defining the perimeter of a high noise level area. Thus, a user can easily determine which areas to avoid, in order to limit their exposure to noise.

The system 1 may use map data and the noise levels with the associated position data in order to determine a navigation path from one place to another. The navigation path may be associated with a reduced level of noise exposure. For example, the system may determine a navigation path from one place to another, avoiding at least one high noise level area. In another example, the system 1 determines noise levels associated with a plurality of different navigation paths from one place to another, and presents the user with the navigation path associated with the lowest noise level. Thus, a user can limit their exposure to noise by following the navigation path.

In addition, the system 1 may notify a user when they have been exposed to a noise level at or over a particular noise threshold. Therefore, the user can be alerted when they have been exposed to an unacceptable level of noise. Then, the user may decide to move to a quieter environment, so that they can attempt to avoid damage to their hearing. Preferably, the user is notified in advance of reaching the noise threshold. In this way, the user can be alerted before they have been exposed to an unacceptable level of noise. The noise threshold may be user-defined. Thus, since some people have higher and lower tolerances to noise, this enables the system to be optimised for individual people.

Referring to Figure 2 and Figure 3, the headset 3 comprises an audio input device 1 1 , a noise level module 13 and a communication interface 15 coupled with an antenna 17. The audio input device 1 1 may be a microphone, or any other suitable audio input device.

In step 300, the audio input device 1 1 receives audio from the environment in which it is located. The headset 3 may be head-mounted or ear-mounted and may be described as a head-mount or an ear-mount. Since the audio input device 1 1 is mounted on the headset 3, the audio input device 1 1 can be used in proximity to the user's ears. Therefore, the system may be able to obtain a more accurate reading of the actual noise level to which the user is exposed. In another example, the audio input device 1 1 may be located in the ear canal of a user.

In step 302 the noise level module 13 determines a noise level based on the audio received at the audio input device 1 1 . Generally, the noise level module 13 will measure the noise level in decibels (dB). However, any other measure of sound/noise level, amplitude or intensity may be used. Noise levels may include sound pressure levels (SPL) and continuous sound exposure levels (SEL), including peak values and specified periods of time. Once a noise level has been determined, the noise level module 13 may output the noise level to a storage module 14 at the noise dosimeter device.

In examples where the audio input device 1 1 is protected from ambient noise levels by a sound reducing headset 3, for instance where the audio input device 1 1 is located in the ear canal of a user, the noise level module 13 can be arranged to estimate the environmental noise derived from the audio input device 1 1 and/or the sound reduction effect of the headset 3. Alternatively, in-ear and environmental sounds may be stored separately at the storage module 14 for SEL and SPL noise calculations respectively.

Noise level data maybe tagged with the sensed sound reduction effect of the headset. Also, noise level data may be time stamped, for instance with the time at which the audio was received from which the noise level data were generated.

Once the noise level has been determined, it is communicated to the computing device 5 via the communication interface 15 and antenna 17. The noise level is received by the computing device 5, via an antenna 19 and communication interface 21 . In this example, the headset 3 and the computing device 5 communicate wirelessly with one other, for instance, via Bluetooth® or via Wi- Fi. However, the headset 3 and the computing device 5 may also communicate with one another via any other suitable connection, such as via a wired connection.

In an alternative example, the audio input 1 1 communicates received audio to the computing device 5 via the communication interfaces 15, 21 to a noise level module 22 at the computing device 5. In this way, the noise level module 13 at the headset can be bypassed or, alternatively, the headset 3 may be provided without the noise level module 13.

The noise level is received by the positioning module 23. In step 304, the positioning module 23 determines the position of the user 4. In one example, the positioning module 23 uses MESHNetworks Position System (MPS™) to determine the position. MPS™ does not rely on satellites, so it can operate in both exterior and interior locations where GPS will not. MPS™ determines position by utilising time of flight and triangulation information using other devices in the network as reference points. In another example GPS is used; however, it will be appreciated that any other suitable positioning system may be used, instead of or in combination with GPS and/or MPS™.

In this example, the positioning module 23 determines the location of the computing device 5. It is assumed that the computing device 5 is either in the user's hand, in the user's pocket or connected with the user in another way. Since the user is wearing the headset 3 which includes the audio input device 1 1 , the positioning module 23 in effect determines the position of the audio input device 1 1 corresponding with the determined noise level. In other words, the positioning module 23 determines an estimate of the position of the audio input device 1 1 at which the audio input device 1 1 received the audio from which the noise level was determined. Thus, in this example the determined position is an estimate; however, a more accurate position may be determined. In step 306, once the positioning module 23 has determined an estimate of the position of the audio input device 1 1 , the positioning module 23 associates the position with the corresponding noise level. For instance, the positioning module 23 may link the co-ordinates of the position with the decibel reading of the noise level.

Steps 300-306 are repeated in order to obtain a plurality of noise level measurements, each associated with a respective position. This helps to build a more complete indication of the noise levels throughout a particular environment. The noise level and position data are stored at a storage module 25 at the computing device 5. The data may be stored at the server 7 as well as at the computing device, or the data may be stored at the server 7 instead of at the computing device.

In step 308, the noise level and position data, from the headset 3 in Figure 2 and the plurality of headsets 3 in Figure 3, are communicated to a mapping module 27 at the computing device 5. In this step, the mapping module 27 generates map data based on the plurality of the positions and associated noise levels. A map of the environment is generated in combination with the map data. This map shows at least some of the determined positions each in association with their corresponding noise level. In step 310, the map along with the map data is displayed at a display/user interface 29 at the computing device 5. The display/user interface 29 may be, for instance, a touch-screen display. An example of the map and corresponding noise data is illustrated in Figure 5. Referring to Figure 4, the display/user interface presents the user with the map 31 of the environment in which various noise levels were recorded. The map 31 shows a number of rooms 32A-C, with passages between them. In this example, the map 31 shows a plurality of areas 33A-C in which noise has been detected. In another example, the map 31 shows a plurality of areas 33A- C in which noise has been detected above a particular threshold.

In this example, the magnitude of the noise levels detected in these areas 33A-C is indicated to the user via shading. A darker shade indicates an area of higher noise level, whilst a lighter shade indicate an area of lower noise level. If there is no shading in an area of the map 31 , the user may assume that no noise has been detected in that area, or that any noise detected is below a threshold.

Any other suitable type of indicator scheme may be used. For example, each area 33A-C may have a numerical value (e.g. between 1 to 10) associated with it. In another example, the user is presented with a noise intensity map comprising contours lines, where the width of the spacing between the contour lines indicate a rise or fall in noise level. Here narrower spacing between contour lines indicates a steep rise in noise level, and wider spacing between contour lines indicates a shallow rise in noise level.

Noise level data from a plurality of users 4 are stored on a central database 7 together with the associated positioning data coordinates. Each of the positioning coordinates relate to a grid reference of the location. The resolution of the square grid reference, or in other words the area of each square in the grid, may be pre-set depending on the accuracy of the positioning apparatus being used.

Noise level data points can be tagged with a grid reference based on the position data. Then, an average of the noise level data can be determined for each square within the grid reference.

The noise levels for each square in the grid are continuously updated by each user who enters the environment. This is useful for constructing a reliable representation of noise levels per unit area. Noise intensity values are derived from the noise level data accorded to each grid reference divided by the assigned area of the grid. The integration of new with old data for each grid map reference may use time related weighting factors.

As a further example, each area may have a particular colour (e.g. green, orange or red) associated with it. Preferably, the indicator scheme used should have a legend so that the user can understand the data presented to them.

On inspection of the map 31 , the user will be able to determine that room 32A has an area of low noise level 33A in its north-west corner, but the rest of the room is quiet; the south end of room 32B has an area of medium noise level 33B, but the rest of the room is quiet; and the whole of room 32C is an area of high noise level 33C. Each noise level area 33A-C has a boundary 35A-C around it, defining the perimeter of each area.

Users may be able to determine for themselves how to get from one point to another, whilst limiting their exposure to noise. However, the mapping module 27 provides a navigation function in which the positioning module 23 determines the position of the user, and the user indicates a destination location 39. Then, the mapping module 27 determines a navigation path which exposes the user to least amount of noise based on the map data. For instance, the mapping module 27 may determine a navigation path that avoids at least one high noise level area. An example of a navigation path 39 is shown on the map 31 in Figure 4. A notification module 45 at the computing device 5, or a notification module 12 at the headset 3, may cause the system 1 to output a notification to the user via the display/user interface 29 at the computing device 5 and/or an audio output 9 at the headset, if the user deviates from the navigation path.

Users can use the map 31 to determine their own paths by themselves, in order to limit their exposure to noise. Alternatively, users may can instruct the device to determine the best route for limiting the users' exposure to noise using the mapping module 27.

In order for the mapping module 27 to determine a route that limits users' noise exposure, the mapping module 27 may identify a noise level limit. Then the mapping module 27 cause the device to display paths from the users location to the intended destination, where the noise level associated with each path is below the noise level limit.

In addition, routing software tools similar to those used in conventional navigation systems may be used, but with preferences such as determining the least noisy route or determining the shortest route which avoids noise levels above a certain threshold. Any deviation from the chosen path may be detected by a rise in noise levels above the selected threshold. This may lead to an audible or visual warning. The user's destination may be indicated by tapping the appropriate area on a pressure sensitive display screen. In addition, the user may be able to zoom-in on areas on the map for closer inspection.

Referring again to Figure 2 and Figure 3, in step 312 a calculation module 43 at the computing device 5 is used to calculate a calculated noise level. The noise level may be calculated based on time data and noise levels determined by the noise level module. The time data may be associated with the noise levels.

The calculated noise level may include a calculation of peak (impulse) noise, equivalent continuous (average) 'A' weighted noise, which is a UK standard, or a time-weighted average (TWA) noise, which is a USA standard. The peak noise, the equivalent continuous noise and the TWA noise are calculated over a predefined period of time, such as over an eight hour period.

Peak noise can be calculated by detecting peak amplitudes of noise. Continuous noise can be sampled over a predefined period of time. Equivalent continuous noise can be calculated by averaging all noise level samples to which a subject is exposed during a period of time, for example, during an eight-hour workday. An average can be calculated through the addition of the magnitude of these samples divided by the number of samples collected during the time period.

TWA noise is the summation of the actual number of hours over which samples are recorded divided by the permissible hours at each sound level multiplied by one hundred for calculating a percentage dose for an eight hour shift.

The equivalent continuous noise level calculation used in the UK uses the "A-weighting standard" for measuring harmful sound pressure level (SPL) values. These weightings take into account subjects' varying susceptibility to noise related hearing damage at different frequencies.

Noise level (L _p ) is a logarithmic measure of the root mean square (RMS) sound pressure relative to a reference (ambient) level expressed in decibels (dB). The A-weighted equivalent continuous noise level, often referred to as energy-averaged exposure level (L _Aeq ), is calculated by dividing the measure dB values by 10, converting to antilog values, assigning an A-weighting curve to them, summing these scaled values, dividing by the number of samples taken and then taking the logarithm to arrive at A-weighted decibels of power dBA. This is illustrated in Equation 1 : L _Aeq = 10 log ₁₀ {1 /n [10 ^L1 _A ¹⁰ + 10 ^L2 _A ¹⁰ + 1 0 ^L3 _A ¹⁰ + ... +10 ^Ln _A ¹ °]} Equation 1

In Equation 1 n is number of samples.

According to UK Occupational H&S requirements the daily value of L _Aeq should lie below 85dBA over an 8 hour period. In another calculation of noise level a C-weighting (L _Cpk ) is used for measuring peak values which according to Occupational H&S should lie below 137dBC. Short L _eq (non A-weighted values) is a method of recording and storing sound levels for displaying the true time history of noise events and all sound levels during any specified period of time. The resulting 'time histories', typically measured in 1 /8 second intervals may then be used to calculate the 'overall' levels for any sub-period of the overall measurement. The time interval (sample time) can be varied according to the amount of change recorded between intervals. To measure true peak values of impulsive sound levels, a meter must be equipped with a peak detector. A peak detector responds in less than 100uS according to the sound level meter standards. A typical response time is 40uS.

A noise dose is a descriptor of noise exposure expressed in percentage terms. For example a noise dose of 160% (87dBA for 8 hours) exceeds the permissible 100% dose (85dBA for 8 hours) by 60%.

The dose value is derived from Equation 2 as follows:

Dose = 100 x T/8 x 10 ^(L _Aeq ^{"85) 1} ° Equation 2

In Equation 2, T is the exposure time. The noise exposure level (L _E x), is the measured L _Aeq of the user's exposure (in decibels) which is linearly adjusted for a fixed 8 hour period. This is illustrated in Equation 3:

L _EX = 10 log ₁₀ {Dose/100} + 85 dBA Equation 3

There may be a pre-defined noise threshold stored at the storage module 25, which the calculation module 43 can access. This noise threshold may be a recommended average noise threshold, such as the Occupational H&S threshold of 85dBA.

In step 314, the calculation module 43 determines whether the noise threshold has been reached. If this threshold has been reached, the method proceeds to step 316 in which the notification module 45 at the computing device 5, and/or the notification module 12 at the headset 3, outputs a notification. The notification module 45 may cause the display/user interface 29 to notify the user that the threshold has been reached and recommend action for limiting exposure to noise. The notification module 12 may cause the audio output device 9 at the headset 3 to output a notification sound.

The noise exposure level defined in Equation 3 above, gives a running account in decibels of the current exposure level adjusted for an eight hour shift which could be compared with the permissible 85dBA threshold.

The system may provide a percentage value of the permissible dose (see Equations 1 and 2 above). 100% may be used as the threshold above which noise induced damaged hearing could occur. Any pre-set threshold should be less than 1 00%.

There are other possible calculations of noise level in percentage terms. For example, a continuous measure of how well the user is doing at managing his/her exposure to noise could also be provided, where the permissible noise dose for an 8 hour shift is adjusted during the shift as illustrated in the example below by using the table in Figure 6. Figure 6 illustrates a look up table that can be used to determine a user's allowable exposure to noise in percentage terms. In Figure 6, L _eq dBA is equivalent to L _Aeq dB. In this example, for the first 2 hours during an 8 hour shift the noise dose exposure level calculated from the table for a L _Aeq reading of 88dBA is 49.9%. This value is divided by the noise dose for the permissible 85dBA reading of 25% for 2 hours to give 200%, which is equal to (49.9/25)x100 . This gives the user a rolling forecast based on current trends which in this case indicates twice the permissible exposure level at the end of the 8 hour shift. However, this method requires the exposure time to be specified and entered by the user using the display device or other such means. An alternate method may be to start a real time clock at the start of each working day and calculate the number of hours left of permissible noise exposure at current noise levels. For example, if the current equivalent continuous noise level L _Aeq over the first hour is 88dBA, the above table calculates that 3 hours remain at current noise levels. This may be useful for diverse working environments.

In another example, a time weighed average (TWA) percentage is output. This would be particularly useful for the North American market.

In another example, at the start of each new day or another defined period should be preceded by an automatic re-setting of the noise exposure data stored in the ear-bud to zero for monitoring exposure levels over this period. Ideally the pre-defined threshold is also stored in the ear-bud which should be the permissible exposure limit (PEL) or a user defined lower (inset) threshold value. A requirement for peak value measurements would require the addition of a peak detector in the ear-bud.

The notification module 45, 12 may also be arranged to output a notification when the noise level at a particular instant reaches a peak noise threshold.

In another example, the calculation module 43 may determine whether calculated noise level has reached a pre-determined level below the noise threshold. For example, the calculation module 43 may determine that the calculated noise level is 10% below the noise threshold. In this case, the notification module 45, 12 may output a notification. Here, the notification module 45 may cause the display/user interface 29 to notify the user that the threshold is about to be reached and may recommend action for limiting exposure to noise. The notification module 12 at the headset 3, may cause an audio output device 9 at the headset 3 to output a notification sound. Therefore, the user can be alerted before they have been exposed to an unacceptable level of noise. Thus, the user can move to a quieter environment, so that they can pre-emptively attempt to avoid damage to their hearing.

In another example, a calculation module 10 at the headset 3 provides the same functionality as the calculation module 43 at the computing device 5. In this way, it is possible for noise level data and subsequent calculations to be processed on-board the headset 3, without having to be transferred to the computing device 5 or the server 7.

Referring to Figure 5, the server 7 in the system 1 comprises a communications interface 49 for communicating with the computing devices 5. The server further comprises a mapping module 51 , which performs a similar function to the mapping module 27 at the computing devices 5, and a storage module 53. Here the server 7 is a network node in the network, which in this case is the Internet.

The mapping module 51 at the server 7 receives a plurality of the positions of the audio input devices from the computing devices 5, each in association with a corresponding noise level. Then, the mapping module 51 generates map data and maps as described above, and illustrated in Figure 4, based on the plurality of the positions and their corresponding noise levels. In this way, the system 1 is able to obtain noise level measurements from different sources. Therefore, it is possible to determine a more accurate indication of the noise level in different locations.

Access to noise level data and/or position data stored at the server 7 may be restricted to authorised users. Users interrogating the server 7 may have the option of retrieving data over specific time intervals. This may be useful for displaying historical trends.

Although different modules have been described as being located at different devices in the system, it will be appreciated that certain modules may be located at any suitable device in the system.

In one example, the functionality of the headset 3 and computing device 4 is integrated into a single device where the audio input 1 1 , the noise level module 13, the positioning module 23, the storage module 25, the mapping module 27, the calculation module 43, the notification module 43 and the display/user interface 29 are part of a single unit rather than being distributed across a separate headset 3 and computing device 5.

In another example, a greater amount of the functionality is delegated to the server 3. In this example, the headset 3 in Figure 2 may comprise the audio input 1 1 , the noise level module 13, the positioning module 23 and the communication interface 15. The server 3 may comprise the mapping module 27 and the calculation module 43 as well as other modules. Here, the server 3 performs the mapping and the calculating from data transmitted directly from the headset 3. In this example, the system 1 may still comprise the computing device which is used to display maps to the user via the display/user interface 29.

The headset 3 may comprise an audio input device for receiving audio from the user, which can be transmitted to the headset 3 of another user. The audio may be transmitted via the communication interface via network. For instance, the audio may be transmitted via a peer-to-peer network, such as a mobile MESH network of a plurality of the headsets 3. The headset 3 may also comprise an audio output device for outputting audio received from the headset 3 of another user via the communication interface.

In some examples, in addition to the headsets 3 and computing devices 5 carried by the users 4, the system 1 may additionally include one or more fixed nodes each being arranged to receive audio from its surrounding environment, determine a noise level, and send the noise level to the server 7. In some examples the fixed node may determine its position, associate this position with the noise level, and send the associated location and noise level to the server. In other examples, each fixed node may send its identity associated to a noise level to the server, since the locations of the fixed nodes are known and fixed the server can then convert the identities to locations, for example by using a look-up table.

The fixed nodes may provide noise data associated with their fixed position for use in producing the noise intensity map. This may remove the need for a user to traverse these expected high noise positions in order to build up the noise information, for example to complete the noise intensity map. This may be useful to limit the exposure of users to noise at known or anticipated high noise level hotspots, which ideally should be monitored in order to keep the noise data and noise intensity map up to date over time. The use of fixed nodes may allow noise levels in areas which are expected to be highly noisy, or are hazardous in other ways, to be monitored without putting users or their hearing at risk. The use of fixed nodes may allow noise levels in areas which are seldom visited by users to be monitored.

In the examples described above, the dosimeter system monitors exposure to noise and outputs noise map data. In other examples the dosimeter system may additionally be provided with suitable sensors to measure other environmental conditions than noise. Examples of such environmental conditions include airborne dust concentration or temperature, such as excessive heat or cold. In such examples the system can additionally measure and track users exposure to these environmental conditions and/or map these environmental conditions in a corresponding manner to that described above for noise.

In other examples the dosimeter system may be provided with suitable sensors to measure other environmental conditions or hazards as an alternative to noise sensors. Examples of such environmental conditions include dust or temperature, such as excessive heat or cold. In such examples the system can measure and track users exposure to these environmental conditions and/or map these environmental conditions in a corresponding manner to that described above for noise. In examples where environmental conditions other than noise are measured the map display, navigation functions and notifications may include other hazards. For example, in a system measuring noise, dust and heat the map, navigation function and notifications may relate to any one or more of noise, dust and heat. In another example, in a system measuring only heat or only dust the map, navigation function and notifications may relate to only heat or only dust respectively.

The methods described herein may be performed by software in machine readable form on a tangible storage medium e.g. in the form of a computer program comprising computer program code means adapted to perform all the steps of any of the methods described herein when the program is run on a computer and where the computer program may be embodied on a computer readable medium. Examples of tangible (or non-transitory) storage media include disks, thumb drives, memory cards etc and do not include propagated signals. The software can be suitable for execution on a parallel processor or a serial processor such that the method steps may be carried out in any suitable order, or simultaneously. This acknowledges that firmware and software can be valuable, separately tradable commodities. It is intended to encompass software, which runs on or controls "dumb" or standard hardware, to carry out the desired functions. It is also intended to encompass software which "describes" or defines the configuration of hardware, such as HDL (hardware description language) software, as is used for designing silicon chips, or for configuring universal programmable chips, to carry out desired functions.

The term 'computer' or 'computing device' is used herein to refer to any device with processing capability such that it can execute instructions. Those skilled in the art will realise that such processing capabilities are incorporated into many different devices and therefore the term 'computer' or 'computing device' includes PCs, servers, mobile telephones, personal digital assistants and many other devices.

Those skilled in the art will realise that storage devices utilised to store program instructions can be distributed across a network. For example, a remote computer may store an example of the process described as software. A local or terminal computer may access the remote computer and download a part or all of the software to run the program. Alternatively, the local computer may download pieces of the software as needed, or execute some software instructions at the local terminal and some at the remote computer (or computer network). Those skilled in the art will also realise that by utilising conventional techniques known to those skilled in the art that all, or a portion of the software instructions may be carried out by a dedicated circuit, such as a DSP, programmable logic array, or the like.

Any range or device value given herein may be extended or altered without losing the effect sought, as will be apparent to the skilled person. It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages.

Any reference to 'an' item refers to one or more of those items. The term 'comprising' is used herein to mean including the method blocks or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subject matter described herein. Aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples without losing the effect sought. Any of the module described above may be implemented in hardware or software.

It will be understood that the above description of a preferred embodiment is given by way of example only and that various modifications may be made by those skilled in the art. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention.