Point taken! But, instead of just adding filters, we did a complete redesign of the hardware. Apart from the microphone cartridge and the preamplifier there is now digital technology everywhere.

We added a new display with higher resolution and backlight, we added a larger memory, we added high-speed data transfer (up to 115200 baud!), we added the real time octave band and third-octave band filters and we extended the dynamic range!

One of the first things you'll notice when using the Nor-118 is that there is no need to set the measurement range -- simple and convenient!

We've added new functionality, but the old Nor-116 had a lot features worth retaining. So we decided to keep the markers, the parallel time constants, the electronic level recorder and the sound power calculations.

And... with filters added the sound power extension becomes handier than ever.

To add further flexibility the Nor-118 accepts prepolarised microphone cartridges as well as the conventional microphone cartridges designed for 200V polarisation voltage.

There is more to this than just providing you with the option of using your existing stock of microphone cartridges -- by reducing the polarisation voltage to 70V (optional extension) the instrument will be able to measure levels up to 150dB peak! The measurement range is then an impressive 20--140dB RMS! Without the need for range setting!

As for all our sound measuring instruments, many of the features in the Nor-118 are optional and can be added upon order or as retrofit whenever required. In this way you don't pay for features never used.

With this article we would like to introduce you to the Nor-118 and explain to you some of its unique features. The Nor-118 is a very powerful sound level meter -- some would say it is more of a palm-size sound analyser -- definitely made to measure!

The modular design of the Nor-118 enables functional expansion to take place when you need it and not necessarily at the time you purchase the instrument. Unlike certain other solutions commercially available, the Nor-118 optional extensions remain in the instrument once installed and activated. There is no need for PC-cards to load and unload the extra modules every time you need other features.

The functions available with the Nor-118 include:

• SPL -- The Instantaneous Sound Pressure Level
• L_MAX -- The Maximum Sound Pressure Level
• L_MIN -- The Minimum Sound Pressure Level
• L_eq -- The Integrated Equivalent Sound Pressure Level
• L_E -- The Sound Exposure Level
• L_PEAK -- The Maximum Peak Level

The spectral weighting functions A- and C- or Z-weighting are available for all functions including the L_PEAK.

The Z-weighting will replace Lin or Flat as these have not been properly defined in any standard. At the time of printing the Z-weighting appears in the IEC DIS 61672 likely to be approved as standard within short time.

As an optional extension the instrument functionality can be expanded to include the ability to measure with all three time constans (F, S, I) applied simultaneously.

The electronic level recorder concept is available in two versions -- basic and enhanced. While the basic version logs the equivalent level, the maximum level and the peak level, the enhanced version is capable of logging any combination of functions available with the Nor-118. In addition it allows source coding.

Another difference important for some applications is that while the basic version has a time resolution ranging from 1 second and upwards, the enhanced version has a time resolution from 100ms and upwards in 25ms steps. Above 1 second the time resolution is available in 1 second steps for both versions.

When fitted with the frequency analysis extensions the Nor-118 can do real time frequency analysis in octaves (8Hz to 16kHz) or third-octaves (6.3Hz to 20kHz).

The functions measured are the equivalent level, the maximum level and the minimum level.

The optional extension 4 adds statistical distribution to the Nor-118 functionality. There are eight percentiles shown, out of which one is freely selectable. The classwidth is 0.2dB over the entire 120dB range.

The statistical distribution calculations employs the F time constant and applies to the spectral weighting networks (A and Z or C) as well as all the individual filterbands (if applicable).

The back-erase feature, which deletes the ten most recent seconds of acquired global data (including the frequency analysis data) prior to a pause upon resuming, updates the statistics buffers as well to maintain consistency. However, the time profile is left untouched so that you will be able to analyse what took place during the pause and thus also during the erased time interval. Profile periods acquired while paused are all marked with a P so that they become easily identifiable in the Nor-Profile post-processing program.

Sound power levels may be calculated from sound pressure level measurements using almost any sound level meter.

However, the methods described in ISO 3744 (octave band and third octave band measurements) and ISO 3746 (A-weighted measurements) involve quite a lot of calculation before you end up with the single figure you need to be able characterise your measurement object.

So, why not let the the Nor-118 take care of this for you? Just specify the measurement surface type (hemisphere or parallelepiped), its dimensions and the location of your measurement object (on the floor, against a hard reflecting wall or in a corner) apply the correction factors and start your measurement. The sound power will then be calculated and displayed in tabulated form.

The large memory and the time synchronising capabilities of the Nor-118 makes it well-suited as a front end in noise monitoring systems -- outdoors for community noise as well as indoors in workshops etc.

The high dynamic range (120dB) makes the setup easy and ensures reliable measurements in all situations.

The Norsonic product range contains a wide range of equipment and accessories for use with noise monitoring and measurements. We supply enclosures for permanent monitoring installations, environmental cases for semi-permanent installations, microphones for applications in tough environments, cables, modems, weather stations and post-processing software.

We made them parallel right away, because you have already told us how important real time frequency analysis is to many of you.

Octave band or third-octave band measurements -- the choice is yours, depending on how you prefer to configure your Nor-118.

The octave band measurements span the range 8Hz to 16kHz, while an upgrade to option 3 will provide you with third-octave band measurements in the range 6.3Hz to 20kHz.

Two bandwidths are available -- octave bands and third octave bands (optional). Roll the mouse over the picture to see a third octave band screenshot.

• SPL -- The Instantaneous Sound Pressure Level
• L_MAX -- The Maximum Sound Pressure Level
• L_^MIN -- The Minimum Sound Pressure Level
• L_eq -- The Integrated Equivalent Sound Pressure Level
• L_E -- The Sound Exposure Level

While the measurement is running the instantaneous SPL is available for inspection, but as soon as the measurement is terminated the SPL becomes meaningless and therefore not listed in the result tables.

If your Nor-118 is equipped with parallel time constants (option 5) the list of functions measured simultaneously can be expanded to include functions with F, S and I time constants at the same time.

The frequency bands measured are all visible in the display with no need for horizontal scrolling. The f-t key lets you enter and exit the spectrum display.

Furthermore, the instrument measures the full frequency range -- every time! Given the high dynamic range (120dB), which eliminates the need for adjusting the gain, there is very little to set up before a frequency analysis can be made -- succesfully!

The measured functions are also available in tabulated form as numerical values. By pressing the TBL key before, during or after a measurement you have instant access to the numerical version. Another push on the key will restore the graphical display.

Adding option 4 to your Nor-118 will expand your frequency analysis to even calculate the statistical level distribution for each frequency band measured! In addition statistics will be calculated for the two spectral weighting networks employed (A- and C- or Z-weighting).

The classwidth is always 0.2dB to ensure sufficient resolution and the results are presented in the form of eight percentiles.

One of these percentiles is subject to user-definition and can be set to anything from 0.1% to 99.9%, both extremes included.

Note that you don't have to define the percentile prior to the measurement. You may redefine the percentile as many times as you like -- even after the measurement! For every frequency band measured!

However, once you store the measurement in the instrument's memory, only the selected percentiles will be available to keep the amount of data lower.

The fixed percentile levels offered by option 4 are 1.0%, 5.0%, 10.0%, 50%, 90%, 95% and 99%.

For the statistical sampling the instrument makes use of the F time constant, irrespective of what time constant(s) the frequency analysis as such employs.

With Nor-118 instruments equipped with the optional extension 6 you will be able to retain all the advantages of the level recorder principle, while at the same time discarding all the trouble!

The optional extension 6 -- level vs. time -- records the time profile of the A-weighted equivalent level, the A-weighted maximum sound pressure level and the Z- or C-weighted peak level -- simultaneously!

The principle is based on dividing the measurement into periods of identical duration. The period duration can be from 1 second and upwards in 1 second steps (from 100ms in enhanced mode).

When a level vs. time measurement is running, the equivalent level will be calculated per period, thus giving you the time profile for the measurement.

The max and the peak levels are also recorded per period so that all three functions will yield a value for every period. Everything is retained within the instrument, hence there is no paper involved in the process!

When you are going to make a measurement, the maximum number of periods at your disposal will depend entirely on the amount of free memory available. It will by no means depend on the duration of each period. This is because a period is a period in the sense that it will occupy a fixed space in the memory, irrespective of its duration.

Given the large memory of the Nor-118 -- the memory can hold approximately 2500000 values (or approximately 12000 measurements. The exact number depends on the number of independent measurements) -- the period duration will for all practical cases be determined by your need for time resolution.

The level vs. time feature is the tool you need for detailed analysis of the time profile. However, a measurement failing to provide an overview of the entire analysis cannot be accepted.

So, we added a global analysis to all time profile measurements. It just runs in the background and makes little fuzz about its presence.

Switching between global and profile is easy, a dedicated key on the front panel -- the Sigma-Delta key -- lets you toggle between the two. The Sigma denotes the global analysis while the Delta denotes the time profile.

Consequently, when you have set up for a time profile measurement by defining the total duration and the time resolution, you have in fact prepared the instrument for two parallel measurements -- the global and the profile!

If exact time information is important, just put the instrument in absolute time mode by pressing the key abs t. All periods will then have the date and time of day they were acquired displayed. If time elapsed since start is sufficient push the key again to return to relative time. This is a display function -- the absolute time is always recorded for all measurements.

After you've defined the duration and the resolution, all you need to do before you press the START key, is to define the time constant and whether to use Z- or C-weighting as the secondary spectral weighting function.

During the measurement you have instant access to the global analysis and profile. For each of these the function key lets you inspect all the functions measured.

For the global analysis the functions measured are the instantaneous SPL, the maximum and the minimum SPL, the equivalent level, the sound exposure level and the maximum peak level. All levels are measured as A-weighted and Z-or C-weighted levels.

The time profile logs the A-weighted equivalent level, the A-weighted maximum sound pressure level and the Z- or C-weighted peak level.

In need of even better resolution or better control of the functions measured?

No problem! The time profile extension can be expanded into the enhanced profile extension -- our option 7 for the Nor-118. Order it when you purchase your Nor-118 or later, if that suits you better.

In the enhanced mode, the instrument logs the time profile of the same functions as with the global:

• SPL -- The Instantaneous Sound Pressure Level
• L_MAX -- The Maximum Sound Pressure Level
• L_MIN -- The Minimum Sound Pressure Level
• L_eq -- The Integrated Equivalent Sound Pressure Level
• L_E -- The Sound Exposure Level
• L_PEAK -- The Maximum Peak Level

If you then add the option 5, parallel time constants, you may set up the instrument to log any combination of functions and time constants, for example the SPL with S time constant and the maximum SPL with F time constant simultaneously.

The enhanced profile has a time resolution which can be from 100ms and upwards in 25ms steps (in 1 second steps above 1 second time resolution), so beware unless you want to create a busy day for yourself -- there will easily be quite a lot of data generated, so avoid more details than strictly needed!

Enter source coding. With the enhanced profile option (see the previous page for more) you may tag or code sources as they happen. A one digit code (which appears in the display as 0--3) is entered to later serve as an identification of the type of noise. This can also be referred to as adding a marker to the measurement.

For example, in a traffic noise measurement a bus passing may be identified by the digit "1", while trucks may be identified by "2", unexpected vehicles by "3" etc. In the profile display the markers appear as dots or lines below the graph. If you move the time cursor onto such a dot, the marker type (i.e. its number) will appear in the display.

During a measurement, adding any of the markers 1, 2 and 3 will assign the corresponding marker number to the current period only. Adding marker number 0, however, will assign this marker to the current period plus all consecutive periods until the marker again is deactivated. A typical application for marker 0 is to denote intervals of particular interest.

The keys used to enter the markers are CAL (marker 1), PRINT (marker 2), EXIT (marker 3) and ENTER (marker 0) since these keys are the lowermost keys of the front panel and thus easy to reach during a measurement. None of these keys are used for other things during a measurement either.

If you hook up your Nor-118 to a computer running our Nor-Profile post-processing software program, the markers will be transferred along with the time profile graph. You will then be able to edit, delete and create markers and marker intervals as well as be able to perform rating analysis on any parts of the time profile.

However, if you upgrade your Nor-118 to include option 10 it will do the calculation for you! A-weighted or in octave or third octave bands! All you need to do is place your test object properly, enter sound power mode, determine the number of microphone positions (the instrument accepts up to 40 positions!) and then start to measure the background noise in one typical position.

This is needed to incorporate the background noise correction K₁.

The measurement surface is either a parallepiped or a hemisphere, placed on a reflecting surface, up against a wall or in a corner. You specify this by selecting P(arallepiped) or H(emispherical) with an additional w(all) or c(orner), when applicable. Then you specify the dimensions of your measurement surface before you key in the acoustic environmental correction K₂.

Once everything is properly defined you just make the measurements in the required positions and the instrument will do all the calculations for you.

A simple push on the tbl key is all it takes to produce the result table containing the L_WA.

In addition to the overall results, the impulsive noise values, the L_PEAKC level and the noise directivity of the test object for all microphone positions are found by sequential pushes on the TBL key.

Operating on its own.
Nor-118 used in noise monitoring systems

With the Nor-118 you are able to do nearly all types of noise measurements -- community noise, industrial hygiene, product control, noise mapping and more.

But, you don?t need to attend the measurement sessions all the time. In fact, the Nor-118 is able to do a lot on its own.

The measurement time can be preset to e.g. 30 minutes or an hour and the instrument put in a mode where it measures and stores the results, then starts measuring again, stores the results, starts measuring again and so on. Each measurement will be stored in a separate file, but all files are stored in the same directory, which has the name of today's date.

In this way the instrument will measure the periods you need. And, do not forget that if this "store and go" feature (which is standard) is combined with the optional time profile each measurement will provide global data and a time profile with a resolution specified by you!

Of course, the instrument will spend a little time storing the data (housekeeping). Therefore, if you start the session with hourly measurements exactly on the hour, long "store and go" sessions will -- after a while -- experience a small, but significant time shift, so that each period no longer starts exactly on the hour.

Enter synchro mode. This feature (standard in all models) stops the measurement slightly earlier to provide time for store and restart. By sacrificing a little at the end of a measurement the synchronisation with the time of day is retained, a feature important to many of our customers.

There is a wide range of accessories and postprocessing software available for the Nor-118 including microphone cartridges, outdoor microphone units for permanent and semi-permanent installations, cases and enclosures, microphone extension cables and PC-to-118 cable, measurement data transfer and postprocessing software.

Random response. The instrument is equipped with a microphone with flat free-field response and satisfies the class 1 requirements in IEC 61672-1 for free-field response. By selecting the random response correction network included, the instrument will satisfy the class 1 requirements in IEC 61672-1 for random response as well as ANSI S1.4-1997 type 1. The nominal correction to obtain flat random response is shown in the figure below.

Windscreen correction. The instrument may be used with windscreen Nor-1451. The windscreen correction has to be switched on to obtain the stated specifications. The nominal correction for the windscreen correction network is shown in the figure below.

OVERALL PERFORMANCE
Nor-118 is a sound level meter complying with: ANSI S1.4-1983 Type 1, ANSI S1.43-1997 Type 1, IEC 60651 type 1, IEC 60804 type 1 and IEC 61672-1, class 1, group X measuring exponential time-weighted levels, integrating-averaging levels and sound exposure levels.

When octave band or third octave band filters are installed, the instrument complies with ANSI S1.11-1986 Type 1D and IEC 61260, class 1.

Dimensions: (WxHxD) 76 x 234 x 32 [mm]; 3 x 9.2 x 1.3 [inches]
74 x 365 x 32 [mm]; 3 x 14.4 x 1.3 [inches] with microphone/preamplifier
Weight: 630g; 1.4 lbs. with batteries

ANALOGUE INPUTS
Number of channels: 1
Input connector: 7 pin LEMO connector
Preamplifier supply voltage: ±17V, max 3 mA
Polarisation voltage: 0V and 200V, selectable.
Maximum input signal: 11Vpeak
Input impedance: >100 kohm and <650pF
Measurement range: 0.3µV to 7V (RMS) in one range corresponding to -10dB to 137dB with a microphone sensitivity of 50mV/Pa. The maximum peak value ±10V corresponds to 140dB. With option 20 (extended measurement range), peak values up to 150dB may be measured.

Highpass filter
The input of the sound level meter is equipped with a highpass filter to reduce noise from wind or other sources with frequencies below the frequency range for measurements.
Filter type: 3rd order HP filter (-3dB at 4Hz, Butterworth response)

Analogue to digital conversion
The analogue input signal is converted to a digital signal by a multirange sigma-delta converter with an effective sampling frequency of 48 kHz. The anti-aliasing filter is a combination of an analogue and a digital filter.

Spectral weighting
Simultaneous measurement of A- and Z- or C-weighting. Octave band or third octave band levels may be measured simultaneously if options providing these weightings are installed.
Octave filters: 8, 16,..., 16000 Hz, class 1 digital IIR filters, base 10 system. (IEC 61260).
One-third-octave filters: 6.3, 8, 10,..., 20000 Hz, class 1 digital IIR filters, base 10 system (IEC 61260).

Level detector
Detector type: Digital true root-mean-square (RMS) detection, resolution 0.1 dB which may optionally be increased to 0.01 dB for indicated levels in the range -9.99 to 99.99 dB.
Crest factor capability: The crest factor is only limited by the peak-value of the signal.

Simultaneous measurement of the following functions: SPL, L_MAX;L_MIN; L_eq; L_E; L_PEAK; Ln (the exceedence level for F-time-weighted sound pressure level, the cumulative distribution); L_eqI; L_EI; L_TMax5.

Indication range
The calibration of the instrument allows microphones with sensitivity in the range -84dB to +15.9dB relative to 1V/Pa to be applied. The corresponding display range for the indicated sound level is -50dB to +180dB.

Self-noise levels
The self-noise is measured with the calibration set to -26.0dB corresponding to a microphone sensitivity of 50mV/Pa. For voltage input the level 0dB then corresponds to 1µV. Typical values for the self-noise are 5dB lower than values stated. Noise measured with 18pF microphone dummy and microphone preamplifier Nor-1206, averaged over 30s of measurement time:
A-weighted: 13dB
C-weighted: 15dB
Z-weighted: 25dB
1/3 oct: 6.3Hz to 250Hz: 10dB (optional)
1/3 oct: 315Hz to 20kHz: 5dB (optional)

Power supply
Batteries: 4 cells, IEC LR6, AA-sized, Alkaline batteries recommended (e.g. Duracell Ultra M3). AA-sized NiCd or NiMH rechargeable batteries may be used, but has to be charged outside the instrument. Battery voltage and time on battery since last change of batteries are indicated.
Typical battery life time: 8h
External DC: 11--15V. Power consumption approximately 1.4W depending on selected modes of operation. External DC source should have an source impedance less than 1W and be able to supply at least 300 mA. If the external supply falls below 9V, the instrument will use the internal batteries if available. Has the instrument switched itself off due to loss of power, it will automatically switch on and resume normal operation after reapplying the external DC supply.

Display
The display is a monochrome, transreflective LCD graphical display with 160×240 pixels (W×H) with automatic temperature compensation for contrast and viewing angle. Applied backlight switches off automatically 2 minutes after the last operation of any key. The bargraph display covers 80dB which may be scrolled in 10dB steps to cover the total range.

Analogue output
Max output voltage: ±10V
Output impedance: <100 ohm. The output is short-circuit proof to ground.
Frequency response re. 1 kHz: ±0.2dB for 100Hz < f < 5kHz, ±1dB for 20Hz < f < 20kHz.
Serial I/O port: RS232 port, 9600--115200 baud

Data storage
Measured data is stored in the internal memory of the sound level meter. The memory is of the "flash" type retaining the information without supply from any battery. Approximately 5 Mbyte is available for the data storage. This corresponds to one of the following examples:

• More than 10000 global measurement with all available global functions and distribution when octave and fractional octave analysis is switched off.
• More than 2 500 global measurements with all available global functions and distribution when octave and fractional octave analysis is active.
• Approximately 2 500 000 samples of L(t) when only one function is logged, corresponding to more than 60 hours with a resolution of 0.1 sec.
• More than 90 000 samples of L(t) when all 28 functions are logged in profile, corresponding to mote than 25 hours with a resolution of 1 sec.

Environmental conditions for operation
Temperature: -10°C to +50°C, max 15°C/hour
Humidity: 5--90% RH, dew point less than 40°C
Atmospheric pressure: 85--108kPa

Environmental condition for storage
Temperature: -30°C to +60°C, max 15°C/hour
Humidity: 5--90% RH, dew point less than 40°C
Atmospheric pressure: 50--108kPa

Some of the features listed in this article may be optional in certain markets. Contact your local representative or the factory for details.

Norsonic reserve the right to amend any of the information given in this leaflet in order to take advantage of new developments.

Copyright © Norsonic AS 2001. All rights reserved

Standard basic version: Integrating impulse sound level meter with parallel A- and C- or Z-weighting and real time octave band filters, 8--16000Hz. Parallel RMS and peak detectors. 120dB dynamic range. Graphical backlit display. Internal memory for storage of up to 2 500 000 values. 115200 baud serial interface. Microphone cartridge Nor-1225, preamplifier Nor-1206, windscreen Nor-1451, carrying case Nor-1331 and instruction manual.

Option 0: LTmax5 and LeqI measurements in accordance with German Standards.

Option 3: Third octave band filters, 6.3--20 000Hz

Option 4: Statistical calculations. 0.2dB class width, 7 fixed percentiles (1%, 5%, 10%, 50%,90%, 95% and 99%) plus one freely selectable (from 0.1 to 99.9%, both extremes included).

Option 5: Parallel F, S, I time constants -- all thre time constants employed simultaneously.

Option 6: Time profile. Electronic level recorder with graphical display and storage of level vs. time of LAmaxF, LAeq and LCpeak or LZpeak with time profile resolution ranging from 1 second in 1 second steps.

Option 7: Enhanced time profile with markers and user selectable functions to be logged with time profile resolution from 100ms in 25ms steps (1 second steps above 1 second resolution).

Option 10: Sound power calculations in accordance with ISO-3744 and ISO-3746

Option 20: Extended measurement range -- up to 150dB peak SPL or low end self noise correction depending on the microphone cartridge used.

Option 21: Display output connector for connection to Video Interface Adaptor Nor-266. Not available as retrofit. Not available in all markets.