SOUND LEVEL METER SOLUTION USER MANUAL SOUND LEVEL METER V21-1 1 SOUND LEVEL METER SOLUTION USER MANUAL 1. Table of contents 1. Table of contents 2 2. About this document 4 2.1. Legend 4 3. Installation 4 3.1. Download 4 3.2. Licensing 4 3.2.1. Evaluation license 5 4. Introduction 5 4.1. Sound pressure level LP (SPL) 6 5. Setup 7 5.1. Microphone calibration 7 5.2. Channel Setup 9 5.3. Naming structure 9 5.4. Sampling rate 10 6. Output channels 11 6.1. Frequency weighting (A, B, C, D, Z) 11 6.2. Time weighting (F, S, I) 11 6.3. Sound Pressure Level (e.g. LAFp) 12 6.4. True Peak Level (e.g. LCpk) 14 6.5. Weighted raw 14 6.6. Equivalent Continuous Sound Level (e.g. LAeq) 14 6.7. Impulse-weighted Continuous Sound Level (e.g. LAim) 15 6.8. Difference Lim-Leq 15 6.9. Max of True Peak Level (Lpkmax) 15 6.10. Sound Energy LE 15 6.11. Max of Sound Level (Lmax) 15 6.12. Min of Sound Level (Lmin) 15 6.13. Percentile levels 16 6.14. Table of output channels 17 7. Measurement & Visualisation 19 7.1. Auto-generated displays 19 7.2. Octave analysis 20 7.2.1. Octave analysis (display) 20 7.2.2. Octave analysis (math) 20 7.3. Standard FFT 22 7.4. Sound Level Octave 3D waterfall diagram 23 8. Offline calculation 23 8.1. Introduction 23 8.2. Waterfall FFT – extracting single lines 24 SOUND LEVEL METER V21-1 2/33 SOUND LEVEL METER SOLUTION USER MANUAL 8.3. Acoustic replay / Analog out 25 9. Export 25 9.1. Print report 25 9.2. Export instrument data to clipboard 26 9.3. Export to Wav, Matlab, Excel... 27 10. FAQ 27 11. Warranty information 27 11.1. Calibration 28 11.2. Support 28 11.3. Service/repair 28 11.4. Restricted Rights 28 11.5. Printing History 28 11.6. Copyright 28 11.7. Trademarks 29 12. Safety instructions 29 12.1. Safety symbols in the manual 29 12.2. General Safety Instructions 29 12.2.1. Environmental Considerations 29 12.2.2. Product End-of-Life Handling 29 12.2.3. System and Components Recycling 30 12.2.4. General safety and hazard warnings for all Dewesoft systems 30 13. Version History 33 SOUND LEVEL METER V21-1 3/33 SOUND LEVEL METER SOLUTION USER MANUAL 2. About this document 2.1. Legend The following symbols and formats will be used throughout the document. Important It gives you important information about the subject. Please read carefully! Hint It gives you a hint or provides additional information about a subject. Example Gives you an example of a specific subject. 3. Installation 3.1. Download “Sound Level” is an option of DewesoftX®, so it already comes with the installation, you just require the license to activate it. 3.2. Licensing In DewesoftX® an additional license for the option is needed, it can also be written into the DewesoftX® device. To test it, you can use a ​30-days-Evaluation license​. SOUND LEVEL METER V21-1 4/33 SOUND LEVEL METER SOLUTION USER MANUAL 3.2.1. Evaluation license You can request an Evaluation license from our homepage: http://www.dewesoft.com/registration (1) Click on ​Evaluation license (2) Fill out all the required fields (3) Click the ​Request ​Dewesoft button Illustration 1: Request Evaluation License Activating the Evaluation license When you have received your trial licence key, open DewesoftX®, go to​ Options / Settings​, select the Registration tab sheet and enter the license code (if you already have other licenses, you may need to click the ​Create ​button). Now enter the license code and click the ​Register Then your new license key will show up in the list online ​button. and should have the ​Status Valid​. Illustration 2: Enter license key Illustration 3: Valid trial license 4. Introduction Per definition, sound is a mechanical wave that is an oscillation of pressure transmitted through some medium (like air or water), composed of frequencies within the range of hearing. SOUND LEVEL METER V21-1 5/33 SOUND LEVEL METER SOLUTION USER MANUAL The human ear covers a range of around 20 to 20 000 Hz, depending on age. Frequencies below we call “infra-sonic”, frequencies above “ultra-sonic”. Sound needs a medium to distribute, the speed of sound depends on the media: ● In air / gases: 343 m/s (1,230 km/h) ● In water: 1,482 m/s (5,335 km/h) ● In steel: 5,960 m/s (21,460 km/h) To understand the proportions, we have to know that we are surrounded by constant atmospheric pressure, while our ear only picks up very small pressure changes on top of that. The atmospheric (constant) pressure – depending on height above sea level – is 1013,25 hPa = 101325 Pa = 1013,25 mbar = 1,01325 bar. So a sound pressure change of 1 Pa RMS (equals 94 dB) would only change the overall pressure between 101323,6 and 101326,4 Pa. Dewesoft Sound Level Meter calculation complies with the international IEC 61672:2013 standard and the SLM software together with our data acquisition systems can be calibrated according to IEC 61672 - ensuring maximum accuracy regardless of the type of measurement you are dealing with. For use with SLM software we recommend SIRIUS DualCoreADC® data acquisition systems. 4.1. Sound pressure level LP (SPL) The most common parameter for characterization is the Sound pressure level, also called Acoustic pressure level or simply “Sound Level”, noted in decibels (dB), and originally referred to the threshold of human hearing (which is by standard “a flying mosquito in 3m distance”). p[RMS] L p = 20 × log ( ) 10 p REF DewesoftX® supports calculation according to ANSI S1.1-1994 for: ● air: pref = 20 µPa ● water: pref = 1 µPa For example, the reference calibrator for microphones, where the microphone is put in before measurement, outputs 1 Pa at 1 kHz. From this we can calculate the dB level. SOUND LEVEL METER V21-1 6/33 SOUND LEVEL METER SOLUTION USER MANUAL Illustration 5: Handheld reference calibrator 1 P a L = 20 × log ( ) = 93, 979 dB p 10 20×10 6 P a Illustration 6: Reference calibrator output 5. Setup 5.1. Microphone calibration Connect the microphone(s), in Channel Setup select “Sound pressure” as Physical quantity, then the following scaling options will appear: SOUND LEVEL METER V21-1 7/33 SOUND LEVEL METER SOLUTION USER MANUAL Illustration 7: Calibration options in DewesoftX® Channel setup To calibrate the microphones there are two options: ● by factor: Enter the sensitivity from the calibration chart of the microphone. ● by calibrator: Put the microphone tip into a Sound Calibrator and click the “Calibrate” button; the Sensitivity will automatically be determined and written into the field on the left side. Illustration 8: Calibration with Sound Calibrator (1 Pa = 94 dB at 1 kHz) It is also possible to calibrate the microphone out of the Sound Level channel setup, please see the next page. SOUND LEVEL METER V21-1 8/33 SOUND LEVEL METER SOLUTION USER MANUAL 5.2. Channel Setup The user interface for the Sound Level is splitted into following sections: ● input: select one or more microphones ● output: depending on your selection, check the output channels and units ● weightings: frequency and time, as well as linear ● main: Sound pressure level, Lpk, and weighted raw channels ● LCpk: C is default weighting, A and linear also selectable ● statistical channels: equivalent continuous sound levels, impulsivity, percentile levels, etc ● calibration: same function as in channel setup; select medium, put microphone into calibrator and press “Calibrate” button Illustration 9: Channel setup of the Sound level option 5.3. Naming structure The user can specify which time and frequency weightings he wants to combine for Sound pressure level, as well as for other parameters. The output format will be “input channel / parameter”. To simplify the graphical user interface, the colors at the end of the parameters show which combinations are possible. SOUND LEVEL METER V21-1 9/33 SOUND LEVEL METER SOLUTION USER MANUAL For example, in the Sound pressure level name “Lp” the letters “Z” for linear and “S” for slow are inserted, resulting in “LZSp”. Illustration 10: Colors for weightings in setup 5.4. Sampling rate As the human ear covers a frequency range from around 20 to 20 000 Hz, we want to measure up to 20 000 Hz. Per theory, the sampling rate should be at least two times the highest frequency you want to measure (Nyquist). A typical used sampling rate is 50 000 Hz. Due to the Sigma-Delta-ADC technology with anti-aliasing filter, at 50 kHz sampling rate the maximum usable bandwidth is 19,531 kHz. The useful range will adapt depending on the selected sampling rate in channel setup, as well as in the FFT instrument. Illustration 11: Sampling rate and bandwidth If you need to get a higher resolution for the upper frequency range, you can (currently) go up to 200 kHz with SIRIUS and 1 MHz with SIRIUS-HS hardware. SOUND LEVEL METER V21-1 10/33 SOUND LEVEL METER SOLUTION USER MANUAL 6. Output channels 6.1. Frequency weighting (A, B, C, D, Z) As the human ear is non-linear (not all frequencies are subjectively recognized with the same loudness level), sound level meters provide the correction / weighting curves. Following corrections can be selected: ● A: mostly used (according to IEC 61672) ● B + D: more or less outdated (D was used for high-level aircraft noise) ● C: for testing purposes of high precision sound level meters ● Z: linear (without weighting) Illustration 14: Equal-loudness curves (©wikipedia) 6.2.