Larson Davis System 824 Training Manual
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Larson Davis System 824 Training Manual

Sound level meter
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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

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  • Page 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...
  • Page 2 The software may not be copied in whole or in part for commercial use without prior written consent of Larson Davis Inc. The manual may not be copied in whole or in part for any use without prior written consent of Larson Davis Inc.

  • Page 3: Table Of Contents

    824 Training Manual Table of Contents Chapter 1 "Quick Start" What you will Learn ..................1-1 Power Key Functions..................1-2 Powering on the 824..................1-2 Battery Life ....................1-2 LCD Screen Backlight ..................1-3 LCD Screen Contrast ..................1-3 An Acoustic Chameleon ..................1-3 Viewing Instrument IDs ................1-4 Navigating the Menus ..................1-5 Arrow Keys ....................1-7 Check key ......................1-7...
  • Page 4 824 Training Manual Printing a Report ..................1-23 Exporting Data ....................1-23 Content of Reports ..................1-23 Summary Report................1 -23 Time History Report..............1-25 Interval Report................1-26 Chapter 2 Environmental Measurements Environmental Noise ....................2-1 Types of Environmental Noise ................2-1 Why Measure Community Noise? ..............2-3 824 LOG Instrument ....................2-4 What Does the LOG Instrument Measure?............2-4 Time History ......................2-4...
  • Page 5 824 Training Manual CNEL ..................2-19 Background Leq ...............2-19 Excd Leq ................2-19 Chapter 3 RT60 Measurements What is an RT60 and how is it measured?..............3-1 RT60 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.......
  • Page 6 824 Training Manual...

  • Page 7: 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 tour of the System 824. After reading this chapter you should be able to do the fol- lowing: •...

  • Page 8: Power Key Functions

        Power Key Functions     Powering on the 824 Turn the 824 on by pressing the On/Off key . The instrument will go through a brief start up cycle, where it flashes the 824 ID screen.     It will then switch to the display that was established before    ...

  • Page 9: Lcd Screen Backlight

    LCD Screen Backlight You can toggle the screen’s backlight on and off by pressing the right arrow key LCD Screen Contrast The screen contrast can be adjusted by continuous presses of . Contrast is expressed as a number between 0 and 100.

  • Page 10: Viewing Instrument Ids

    Each of these instruments are available from the Setup menu. Viewing Instrument IDs Push the Setup key to view the instruments (virtual instruments) in your 824. Integrating sound level meter - Measures Leq, SEL, Min, Max, Peak, with all weights (A, C, Flat) and with all detectors (Slow, Fast, Impulse) simultaneously.

  • Page 11: Navigating The Menus

    Navigating the Menus The main menu keys are shown below. To access the differ- ent instrument functions, simply press the appropriate key. Figure 1- 1 View, Data, Setup, Tools, and Print Keys. The PRINT The DATA The SETUP The TOOLS The VIEW key is used to store a key is used to estab-...
  • Page 12 The PAUSE key suspends measure- ment. Pressing the pause The RESET key This is the RUN/ key again will allow the is used to clear the cur- STOP key. It initiates or measurement to con- rent measurement from ends a measurement. tinue.

  • Page 13: Arrow Keys

        Arrow Keys The four arrow keys are used to navigate through each selected menu and display..When displaying data the up and down arrow keys move through display screens. The left and right arrow keys move the user from one related screen to the next.

  • Page 14: Ssa Measurements

    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.
  • Page 15 Metric Explanation of Metric SPL Fast (dBF) SPL Fast (dBC) SPL Fast (dBA) SPL Slow (dBF) The instantaneous SPL of the given frequency and time SPL Slow (dBC) weighting found at the end of the period. SPL Slow (dBA) SPL Impl (dBF) SPL Impl (dBC) SPL Impl (dBA) RTA Leq...

  • Page 16: Interval History

    Interval History Another history available to the SSA is the Interval History. This statistical history provides a number of parameters cal- culated over a period of time that can be set from 1 second to over 99 hours. Below is a level versus time graph showing four interval periods: Level Level versus Time Graph...

  • Page 17: Broadband Measurements

    For each Interval period the following can be optionally selected: 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 were over for n% of the time Min spectrum(bin by bin minimum) Lowest instantaneous level reached for each frequency band during the interval.
  • Page 18 Metric Explanation of Metric SPL Fast (dBF) SPL Fast (dBC) SPL Fast (dBA) SPL Slow (dBF) The instantaneous SPL of the given frequency and time SPL Slow (dBC) weighting found at the end of the measurement. SPL Slow (dBA) SPL Impl (dBF) SPL Impl (dBC) SPL Impl (dBA) Lmax Fast (dBF)

  • Page 19: Lets Go For A Test Drive

    Lets Go For a Test Drive Now that we know what the SSA instrument will measure, let’s setup the 824 to take a simple measurement. Step 1 Push the SETUP key to get into the SETUP menu. Your screen should look like the one below: Step 2 If your screen doesn’t look like this despite anything that you do, the...

  • Page 20: Intervals

    • Bandwidth [1/3] Intervals • Intv Enable [No] Time History • Hist Enable [No] • Enable Ln [No] For now we will not change any settings for Triggering, Define Report, and Controls. We will rely on the default settings. We did not turn on the Interval History, Time History, or enable the Lns (statistical data).
  • Page 21 Settings Menu and Submenus 4/19/01 824 “Quick Start” 1-15...
  • Page 22 Settings Menu and Submenus (continued) 1-16 824Training Manual 4/19/01...

  • Page 23: Resetting Data

    Resetting Data Step 8 At this point it is a good idea to reset the 824 for a new measurement. Press the RESET key, select “OverAll” then press the Check key. Calibration Step 9 Calibrate the 824 according to the procedure found in chapter 2 of the 824 Reference Manual.

  • Page 24: Rta Data

    Refer to page 1-12 or the 824 Refer- With “Any Level” highlighted, press the Check ence Manual for an explanation of again. To scroll through the different displays use the right these metics and displays. and left arrow keys You will see that metrics for A,C, and Flat and Slow, Fast, and impulse are all measured simultaneously.

  • Page 25: Download Data Using 824 Utility Software

    Press the Check key to bring up the Data Files display. As you can see this display shows the total number of records and the current record you are viewing along with the date and time the record was taken. Use the up and down arrow keys to select the record you would like to recall and press the Check key.

  • Page 26: Downloading The Data

    printed directly from the 824 Utility software or from your Excel file. Downloading the Data For this exercise you will need to have already installed the 824 Utility software on your computer and connected the CLB006 computer interface cable between the 824 and the serial port on your computer.
  • Page 27 Use the note facility to identify your measure- ment before hitting the download button. Step 4 You will notice on the left hand side of the win- Use the “Ctrl” key of your computer in conjunction with your mouse to dow shows the measurements that are stored in the select more than one measurement.

  • Page 28: Translating The Data And Looking At The Reports

    • “Save binary data” • De-select “Launch viewer of type” • From “Translate the following records” click on the “Select All” button. Step 7 Click on the “OK” button to start the download. A window will appear showing the status of the download.

  • Page 29: Reports (824 Utility Software)

    Reports (824 Utility Software) Once the report is displayed on the right side of the window it can be printed or exported to a spreadsheet for viewing. Printing a Report To print the report you are viewing, select “File” and then “Print”.
  • Page 30 6 Ln statistical values over the run time of the 824 showing the distribu- tion of the SPL exceeded n% of the time. Shows values for each filter for Leq spectra, @Max spectra, and Min spectra. 1-24 824Training Manual 4/19/01...

  • Page 31: Time History Report

    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 explained on page 1-9. 4/19/01 824 “Quick Start” 1-25...

  • Page 32: Interval Report

    Interval Report The 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 and analyzing capabilities of the 824 and software.

  • Page 33: Chapter 2 Environmental Measurements

    C H A P T E R Environmental Measurements Because of its features, ruggedness and tolerance to environ- mental extremes the System 824 is uniquely qualified for environmental noise monitoring. Environmental Noise Environmental noise impacts our quality of life. It can cause annoyance, hearing loss, stress, and loss of sleep.
  • Page 34 - Small airport systems - New developments around airports and land use planning - FAR 36 testing of airplanes (FAA operations) - Encroachment on wilderness areas and National Parks - Military overflights and sonic booms • Railroad noise - Locomotive noise, whistles, switching opera- tions - Rail car retarders can produce up to 120dB peak at 100 feet away...

  • Page 35: Why Measure Community Noise

    • Product noise - Noise from power tools, appliances, office prod- ucts, lawn mowers, etc. - Acoustic measurements normally done by manu- facturer • Recreational noise - Recreational vehicle noise (snow mobiles, power boats, jet skis, off road vehicles, etc.) - Events and venues such as outdoor concerts, race tracks, theme parks, amusement parks, etc.

  • Page 36: What Does The Log Instrument Measure

    824 LOG Instrument The 824 LOG instrument was designed and configured to measure all types of environmental noise, thus the name “LOG”. It is designed for long-term recording and contains several histories to help you, the environmental noise ana- lyst, to get the most from your measurement time in the field.
  • Page 37 Below is a level versus time graph showing several time his- tory periods: Level Level versus Time Graph Time Time Time Time Time Time Time Time Time History history History History history history history history Period period Period Period period period period period...

  • Page 38: Interval History

    See page 1-9 for a description of each of these metrics. Interval History Another history available to the LOG instrument is the Inter- 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.

  • Page 39: Special Advanced Feature

    For each Interval period the following are recorded automat- ically: Metric Explanation of Metric Leq (dB) w/selected weighting Short Leq average of all energy during interval SEL (dB) w/selected weighting SEL of all energy during interval Lmin (dB) w/selected weighting Minimum instantaneous SPL during the interval Lmax (dB) w/selected weighting Maximum instantaneous SPL during the interval...

  • Page 40: Exceedance History

    Below is an illustration showing when each new interval will begin based on the Interval setting: 10 minute 15 minute 5 minute 60 minute 30 minute 20 minute Exceedance History The Exceedance History is a special history of events which go over a set threshold.
  • Page 41 Level (dB) Exceedances SPL Excd Level 1 Level versus Time Graph Time Total time of measurement Let’s take a closer look at what constitutes an exceedance. Below is a detail of one of the peaks shown in the previous graph. START Duration Lmax...

  • Page 42: Exceedance Time History

    An exceedance begins when the instantaneous SPL is found to be greater than the trigger level (SPL Excd Level 1) or when the instantaneous Peak I or Peak II levels are found to be over their respective trigger levels (Pk-1 Excd Lvl and Pk-2 Excd Lvl).

  • Page 43: Setting The Parameters For An Exceedance History

    Below is a graph of a time history for an exceedance: dfdsasdfdsafffffffffffffffffffffffffffffd dfdfsasdf Sampling rate from 1/32 of a second to approx. 8 seconds -9 -8 -7 -6 -5 -4 -3 -2 -1 +1+2 +3 +4+5+6+7 +8+9 Up to 118 samples 10 samples recorded after the event 10 samples recorded before the event Hint:...

  • Page 44: Excd Enable (Yes)

    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 Time (Start) 2-12 824 Training Manual 3/22/01...
  • Page 45 Exceedance History & Triggering Menus Trigger Menu Exceedance History Menu 3/22/01 Environmental Measurements 2-13...

  • Page 46: Viewing Exceedance History Data On The 824

    After configuring the 824, press the RUN/STOP key to begin a measurement. Since the “SPL Excd Level 1” is set to 70 dB, you will need a noise source which is louder than 70 dB to trigger an exceedance. Whistle near the microphone for a few seconds while moni- toring the sound level (make sure the level goes over 70 dB) to trigger an exceedance.

  • Page 47: Time History

    Time History From either the “Excd-a” and “Excd-b” displays, press the Check key to access the “Time History” display. The Exceedance time history is triggered off of the selected detector and uses a short Leq function to show actual energy. PassBy Exceedance When the parameter, “Excd Trigger”, is set to “Passby”...

  • Page 48: Passby Measurement

    The largest passby event will be shown in the PassBy view. PassBy Measurement Whether or not you turn on the Exceedance history, the PassBy function will automatically record the highest passby to occur during the run time of the instrument. You don’t have to enable the Exceed- To access this display, press the VIEW V key, scroll down to ance History to get a passby mea-...

  • Page 49: Explanation Of Ldn And Cnel

    The measurement period is from 12:00 midnight to 12:00 midnight each day. Use the a rrow keys to step between the two Daily displays. Explanation of L and CNEL and CNEL are similar to a 24 hour Leq except the night- time hours are weighted.

  • Page 50: Hourly Leq

    Hourly Leq The Hourly Leq is the equivalent sound level calculated over an hour period for each hour during the day. Background Leq Background Leq can be considered The Background Leq is the total hourly energy (hourly Leq) the Leq expected if the exceedances minus the total energy (event Leq) of any valid event during had not occurred.

  • Page 51: Dnl (Ldn)

    Use the a rrow keys to step between the two Metrics displays. DNL (L The DNL (Day-Night Average Sound Level) is the equiva- lent sound level for the entire measurement period with a +10 dB weighting applied to all sounds occurring between the time of 10:00 PM to 7:00 AM.
  • Page 52 2-20 824 Training Manual 3/22/01...

  • Page 53: Rt60 Measurements

    C H A P T E R RT60 Measurements The versatility of the 824 includes the measurement of RT60 or reverberation time. This capability combined with advanced triggering features allows the use of a noise gener- ator without an interconnecting cable to the 824. Those of you involved in determining decay times of rooms, theatres, or any acoustic space designed for a specific acous- tic application or in analyzing the absorptive qualities of...

  • Page 54: How Does My 824 Measure An Rt60

    the level by some dB for some time and extrapolated to obtain a time for a 60 dB drop How does my 824 measure an RT60 measurements are usually made with real-time analyz- RT60? ers with 1/3 octave filters. The 824 uses the high speed RTA option to gather spectra at a rate of up to 400/second.

  • Page 55: Taking An Rt60 Measurement

    Taking an RT60 Measurement This next section will take you through a step by step pro- cess for acquiring an RT60 measurement. Exciting the Room To find out the absorption qualities of a particular room using an RT60 measurement, you will have to energize the room with some sound source.
  • Page 56 RT60-A Settings Menu and Submenus 824 Training Manual 3/22/01...
  • Page 57 See the 824 Reference Manual, Since the RT60-A setup is already configured to take a mea- chapter 10, for details concerning surement using steady state noise, let’s setup our generator each of the setup parameters. and speaker to energize a room with noise. Place your 824 on a tripod out of the near field...
  • Page 58 Step 4 You will need to configure your generator (Larson You can trigger your pink noise ON & OFF manually though you may Davis SRC20) to output pink noise in pulse mode find pulses of noise more convenient. with an ON time of 2 seconds and an OFF time of 5 seconds.

  • Page 59: Advanced Rt60 Measurements

    Step 7 Press the VIEW key, highlight “Autostore” and press the right arrow key. Select RT60 and press the Check key. To easily access the RT60 menu to With the “Auto-Select” feature selected, a vertical line or change the “RT60 dB Down” cursor will be positioned on the time sample that is 5 dB parameter, press the Check below the maximum level.
  • Page 60 Stop, Ready, Armed, Triggered, End/Then STOP Ready Arm conditions met Gather pretrigger data Armed Trig conditions met Triggered End conditions met Gather triggered data End/Then Then Repeat or Average Then Stop or Repeat done or Average done Arms when the selected Triggers when the selected Ends when the selected condition is met...

  • Page 61: Customizing The Trigger Menu

    Customizing the Trigger Menu Following the diagram below, access the trigger settings by pressing the SETUP key. With “Edit Settings RT60-A” highlighted press the Check key. Scroll down to “Trigger Setup” and press the right arrow key. From here you can cus- tomize the trigger settings for a particular application.

  • Page 62: End Time

    A pulsing noise generator may be Press the RUN/STOP key on the 824 to put the 824 in the very helpful. Each pulse can trigger “Ready” mode. Start the generator to energize the room with a new measurement without any user noise.
  • Page 63 The following diagram shows the key presses necessary to view the Leq and Max displays: From the Leq, Max, or Min display, pressing the up a nd down a rrow keys will take you from one autostore record to the next. Pressing the Check key will put you in the “Autostore”...
  • Page 64 3-12 824 Training Manual 3/22/01...
  • Page 65 824 Training Manual Index Numerics Environmental Noise ......2-1 Excd Leq ..........2-19 824 configurations ........1-3 Excd Time ..........2-12 Excd Trigger ........... 2-12 Exceedance History ........ 2-8 advanced feature ........2-7 Exceedance Time History ...... 2-10 Aircraft noise .......... 2-1 Exporting Data ........
  • Page 66 824 Training Manual SLM Data ..........1-17 slope ............3-2 LCD Screen Backlight ......1-3 Sound spectrum analyzer ....... 1-4 LCD Screen Contrast ......1-3 SSA Measurements ........ 1-8 Ldn ............2-17 Storing Data ..........1-18 Level versus Time Graph ....... 1-8 Summary Report ........

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