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Larson Davis System 824, Руководство по обучению

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1-8

824Training Manual

4/19/01

SSA Measurements

The most frequently used instrument of the 824 is the Sound
Spectrum Analyzer or SSA. The SSA instrument includes
frequency analysis with sound level meter functions. Lets
take a look at what the SSA instrument can measure.

Time History

The Time History records time segments down to 1/8th of a
second. The Time History is intended for a more detailed
look at the data versus time. The time history is valuable at
detecting what might be the offending noise source(s).

Below is a level versus time graph showing several Time
History periods:

The graph is divided into eight equal time history periods.
The duration of each period can be adjusted from one-eighth
of a second to 255 minutes.

For each Time history period you can select any of the fol-
lowing to be recorded:

Time

Level

Level versus Time Graph

Time
History
Period
1

Time
History
Period

2

Time 
History
Period
3

 

Time
history
period
4

Time
history
period
5

Time
history
period
6

Time 
history
period
7

Time
history
period
8

Содержание System 824

Страница 1: ...System 824 Training Manual Larson Davis Inc 1681 West 820 North Provo UT 84601 USA Phone 801 375 0177 FAX 801 375 0182 www LarsonDavis com I824 02 Rev C...

Страница 2: ...ity or fitness for a particular pur pose This documentation is subject to change without notice and should not be construed as a com mitment or representation by Larson Davis Inc This publication may...

Страница 3: ...Some Buttons 1 7 SSA Measurements 1 8 Time History 1 8 Interval History 1 10 Broadband Measurements 1 11 Lets Go For a Test Drive 1 13 SLM 1 13 RTA 1 13 Intervals 1 13 Time History 1 13 Ln 1 13 Resett...

Страница 4: ...ecial advanced feature 2 7 Time synchronization 2 7 Exceedance History 2 8 Exceedance Time History 2 10 Setting the parameters for an Exceedance History 2 11 Excd Enable Yes 2 12 Min Duration 000 2 12...

Страница 5: ...T60 Defined 3 1 How does my 824 measure an RT60 3 2 Taking an RT60 Measurement 3 3 Exciting the Room 3 3 Setting up the 824 for an RT60 measurement 3 3 RT60 A and RT60 B Setups 3 3 Advanced RT60 Measu...

Страница 6: ...824 Training Manual vi...

Страница 7: ...r it a getting started guide as you get to know your 824 What you will Learn This manual is best used accompanied with the instrument and 824 Reference Manual You will be guided through a step by step...

Страница 8: ...ay that was established before it was powered off in its previous session The On Off key can also be used to check the battery power as well as verify the on off status of the display s backlight Pres...

Страница 9: ...xit the PWR screen An Acoustic Chameleon Even if you didn t purchase some of the options demo versions are pro vided of all of the optional virtual instruments The 824 is a quick change artist and can...

Страница 10: ...ce history daily history Ln percentiles statistical data exposure and dual SLM current and overall Real time analyzer High speed spectral data gathering of up to 400 spectra per second using Autostore...

Страница 11: ...ure ment setup you have selected The PRINT key is used to estab lish the settings required to communi cate with an external serial printer and to select the type of report to print The TOOLS key is us...

Страница 12: ...will clear and a new measurement can be acquired The PAUSE key suspends a measure ment Pressing the pause key again will allow the measurement to con tinue Pressing the pause key when the 824 is stop...

Страница 13: ...When modifying a setting the left and right arrow keys select a character or digit to modify The up and down arrow keys will modity the parameter Check key The check key is used to select an option o...

Страница 14: ...ta versus time The time history is valuable at detecting what might be the offending noise source s Below is a level versus time graph showing several Time History periods The graph is divided into ei...

Страница 15: ...ax Slow dBC Lmax Slow dBA Lmax Impl dBF Lmax Impl dBC Lmax Impl dBA Lmin Fast dBF The lowest instantaneous SPL during the period Lmin Fast dBC Lmin Fast dBA Lmin Slow dBF Lmin Slow dBC Lmin Slow dBA L...

Страница 16: ...nterval 1 Interval 2 Interval 3 Interval 4 1 sec to 99 hrs 1 sec to 99 hrs 1 sec to 99 hrs 1 sec to 99 hrs Metric Explanation of Metric Leq dB w selected weighting Short Leq average of all energy duri...

Страница 17: ...rics are recorded Metric Explanation of Metric Six Ln values broadband The level that the instantaneous SPL was over for n of the time Six spectral Lns Six spectral Lns whose frequency band levels wer...

Страница 18: ...s SPL during the measurement Lmin dBC Lmin dBA SEL dBF Sound exposure level during the measurement Leq 10 Log T where T is in seconds SEL dBC SEL dBA Peak dBF The largest peak level achieved during th...

Страница 19: ...rrow to enter into the SSA settings menu For an explanation of any of these settings please see chapter 7 of the 824 Reference Manual You will notice that you have alot of choice concerning the setup...

Страница 20: ...enable the Lns statistical data For this measurement we will only record SLM RTA broadband data over the run time of the instrument Step 5 Once you have completed configuring the 824 back out of the t...

Страница 21: ...4 19 01 824 Quick Start 1 15 Settings Menu and Submenus...

Страница 22: ...1 16 824Training Manual 4 19 01 Settings Menu and Submenus continued...

Страница 23: ...e 824 Reference Manual Taking a Measurement Step 10 Press the RUN STOP key to start taking a mea surement Let the instrument run for about a minute then press the RUN STOP key again to stop the measur...

Страница 24: ...neously RTA Data To view the RTA data press the VIEW key and back out to the main VIEW menu by pressing the left arrow key Highlight RTA from the VIEW menu and press the right arrow Highlight RTA Live...

Страница 25: ...e VIEW menu From the VIEW menu you can view the data that is impor tant to you Download Data Using 824 Utility Software Using the 824 Utility software allows you to download the data files stored in t...

Страница 26: ...omputer Refer to chapter 9 of the 824 Reference manual if you need help getting to this point Step 1 Run the 824 Utility software by clicking on the icon on your desktop Step 2 Connect the 824 to your...

Страница 27: ...or all of the same type of measurement Let s select the first measurement for download LM RTA The file will automati cally be named using the date the measurement was taken on You have the option of...

Страница 28: ...ports To get the data into a form that we can look at we need to translate it To translate the data click on the translate win dow button on the tool bar The translate window is shown below To look at...

Страница 29: ...readsheet select File and then Export Data or View Data in a Spread sheet The report will be printed in the format you see on the screen For some reports such as the Time History report you may need t...

Страница 30: ...raining Manual 4 19 01 Shows values for each filter for Leq spectra Max spectra and Min spectra 6 Ln statistical values over the run time of the 824 showing the distribu tion of the SPL exceeded n of...

Страница 31: ...Start 1 25 Time History Report The Time History report shows each time history sample selected for the time history period For each time history period you can record up to 37 data parameters as expl...

Страница 32: ...e Interval report shows the data for each interval period See page 1 10 for explanation of data parameters for interval history That s the basics Now you can move on to some more pow erful measuring a...

Страница 33: ...lity of life It can cause annoyance hearing loss stress and loss of sleep The num ber of noise sources are increasing on a daily basis For those involved in measuring analyzing and processing of envir...

Страница 34: ...ajor projects usually require an environmental impact study roadways new plants mines etc May require permanent noise monitoring system Industrial noise Industrial noise may come from machinery such a...

Страница 35: ...tc Firearms small arms ranges Why Measure Community Noise Community noise is measured for a lot of reasons but mostly because someone is being annoyed by some noise source Here are some other reasons...

Страница 36: ...OG instrument has the following histories Time History Interval History Excd History Daily History In addition to the Histories the LOG instrument measures the following Current Overall levels Six Ln...

Страница 37: ...me History Period 3 Time history period 4 Time history period 5 Time history period 6 Time history period 7 Time history period 8 SPL Fast dBF SPL Impl dBC Lmax Slow dBA Lmin Slow dBF Peak dBC SPL Fas...

Страница 38: ...nter val History This statistical history provides a number of parameters calculated over a period of time that can be set from 1 second to over 99 hours Below is a level versus time graph showing fou...

Страница 39: ...ws each inter val record for example to begin at the start of each new hour of the day Syncing can be done to the following incre ments of time 1 minute 5 minutes 10 minutes 15 minutes 20 minutes 30 m...

Страница 40: ...y The Exceedance History is a special history of events which go over a set threshold For each exceedance history the fol lowing are recorded Duration Leq Lmax SEL Peak I Peak II Time and date of occu...

Страница 41: ...look at what constitutes an exceedance Below is a detail of one of the peaks shown in the previous graph Level dB Level versus Time Graph Total time of measurement Exceedances Time SPL Excd Level 1 S...

Страница 42: ...t ended The Leq and SEL are calculated over this period The Lmax is the largest instantaneous SPL achieved during this period Exceedance Time History A time history of the exceedance can be recorded a...

Страница 43: ...commended that you get familiar with the type of events you would like to capture Remember that the data recorded in the Exceedance history are Duration Leq Lmax SEL Peak I Peak II time and date of oc...

Страница 44: ...aining Manual 3 22 01 Triggering SPL Excd Lvl 1 70 SPL Excd Lvl 2 90 Pk 1 105 Pk 2 Excd Lvl 100 Hysteresis 2 Excd Enable Yes Min Duration 000 Excd Time Hist Yes T H Period 032 Excd Trigger Level Excd...

Страница 45: ...3 22 01 Environmental Measurements 2 13 Exceedance History Triggering Menus Trigger Menu Exceedance History Menu...

Страница 46: ...70 dB to trigger an exceedance Allow the meter to run for several seconds after triggering the exceedance in order for the level to drop below the hysteresis level Press the RUN STOP key to stop the m...

Страница 47: ...and SEL of the highest event to raise and lower 10 dB in SPL It is used to capture single events such as a vehicle or aircraft passby or other event noises such as blasts or gas jetting noise as requ...

Страница 48: ...By under the Excd Trigger setting The data for the PassBy function can be stored manually To access this display press the VIEW V key scroll down to PassBy and press the Check c key For the passby mea...

Страница 49: ...hours of 10 00 PM to 7 00 AM CNEL is similar to Ldn except that 5 dB is added to the mea surement levels between 7 00 PM and 10 00 PM and 10 dB are added between 10 00 PM to 7 00 AM These measurement...

Страница 50: ...change of the hour Since most events are rather short in duration the hour is extended until the exceedance ends up to 30 seconds If after 30 seconds the exceedance has not ended the exceedance is spl...

Страница 51: ...ed between 10 00 PM to 7 00 AM These measurements are used because people tend to be more sensitive to noise during the nighttime and early morn ing hours Background Leq Background Leq can be consider...

Страница 52: ...2 20 824 Training Manual 3 22 01...

Страница 53: ...easurements are used to determine the sound absorption characteristics of a room This is also known as the reverberation time or the decay time The reverberation time in a room at a given frequency is...

Страница 54: ...e records show each time slice 2 5mS as the sound is decaying in the room The ByTime display of the 824 shows each of the 1 3 octave frequencies over time The following diagram shows the level versus...

Страница 55: ...60 measurement For an RT60 measurement use the RTA instrument of the 824 Step 1 To select the RTA instrument press the SETUP key Use the up and down arrow keys and high light either RT60 A or RT60 B a...

Страница 56: ...3 4 824 Training Manual 3 22 01 RT60 A Settings Menu and Submenus...

Страница 57: ...test will be free of interference Caution Wear hearing protection when generating noise levels of 90 dB or more Remember that levels will be greater near the noise source Make sure you can energize t...

Страница 58: ...he Trigger Status display will show these four states sequentially as the measurement is taken Stop Ready Armed Triggered NOTE Triggering is performed on one frequency band or Flat as selected by the...

Страница 59: ...int Due to the differing geometries and acoustic characteristics of some rooms a perfectly linear decay curve may not always be obtained Using the left land right rarrow keys a custom start point can...

Страница 60: ...or a certain amount of time Level is equal to or greater then or less then a preset level for a certain amount of time Logic In line changes Logic In line changes Logic In line changes A preset amount...

Страница 61: ...erage data does not take any additional memory Each additional measurement will be averaged insitu with the first The END condition must be TIME or SAMPLES so that the records are all identical length...

Страница 62: ...suring may have a shorter or longer reverberation time than the 3 seconds selected in the End menu If the reverberation time is much shorter it is not necessary to store additional unneeded samples wh...

Страница 63: ...e record to the next Pressing the Check key will put you in the Autostore check menu From the Autostore check menu you can view the ByTime spectra and ByTime graph each frequency over time NOTE If an...

Страница 64: ...3 12 824 Training Manual 3 22 01...

Страница 65: ...rts 1 23 D Daily History 2 16 date of occurrence 2 11 Download Data 1 19 duration 2 10 E End Time 3 10 Environmental Noise 2 1 Excd Leq 2 19 Excd Time 2 12 Excd Trigger 2 12 Exceedance History 2 8 Exc...

Страница 66: ...ng Data 1 18 Recreational noise 2 3 Reports 1 23 Resetting Data 1 17 Road traffic 2 1 RT60 Defined 3 1 RTA Data 1 18 S screen contrast 1 3 Short Leq 1 10 simple measurement 1 13 SLM Data 1 17 slope 3...

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