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NOMISSOFT GmbH
Description of sound level meter | Explanation of symbols and abbreviations
Description of Sound Level Meter
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Our measurement station is based on the Sound Level Meter "PeakTech 8000", serial number 2997455, of the manufacturer Heinz-Günther Lau GmbH. The Sound Level Meter is positioned in the 4th floor on the southern balcony of the apartment Top 406, one meter in front of the (noise cancelling) window and therefore overlooks the whole area of the "Heizkraftwerk Mitte". Other significant sources of noise are traffic as well as a railroad line and bridge over the river Salzach. The Sound Level Meter has a RS-232C interface, which delivers the current measurement data to our (Linux based) Web-Server, which processes and stores each result including timecode into a database. About 160000 measurement data are processed and stored per day. Each data represents the average (=energy equivalent) level over 0.3 to 0.7 seconds ("slow" mode). Therefore extreme peaks caused by impulse containing sounds (e.g. pneumatic hammer) can not be registered. Within our Web-Server a specially developed CGI-script reads the database, prepares the measurement data for graphical display and calculates the energy equivalent sound levels for the various periods. The software also computes loudest and most silent 30 seconds and 30 minutes for each day. The graphics (24-hour drum) displays all measured data over 60 db(A), showing the whole period of time in blue, the loudest half hour in orange, the loudest 30 seconds in brown, the most silent 30 minutes in purple and the most silent 30 seconds in green. Alle data exceeding 80 db(A) are displayed in red however. Detailed displays - up to displaying each separate measurement data - can be called by clicking onto the graphics. A click into the graphics display brings the surrounding 30 minutes up in detail, a click onto a text line at the bottom of the graphics or below displays the according time interval. Within the detail graphics you can zoom in further by clicking into the left or right half of the display - the according first or second half will be expanded. The detailed graphics shows each according db(A) value und computes the energy equivalent level as well as L01 and L95 for the displayed period of time. You can zoom into the graph by clicking the left or right half of the display unless the period display is already less or equal 30 seconds. |
Explanation of symbols and abbreviations
| dB(A) | The Soundlevel is calculated in decibel (dB). As the human ear perceives different frequencies and volumes differently, an adopted level db(A), which follows the human perceiption, is being used for assessment of sounds. 20 db(A) are about equivalent the ticking of a fob watch, 30 db(A) are produced by whisper, 50 db(A) are produced by a quiet discussion, 70 db(A) by a loud discussion, 80 db(A) are perceived as very loud, 120 db(A) result in pain. An increase of 3 db(A) means double the energy, an increase of 10 db(A) however means, that the human ear perceives the sound twice as loud. An average healthy human ear will notice a change of 1 db(A) or more. |
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| L01 | marks that sound level, which is exceeded in 1% of the measurement period. That level is used to suppress single peaks. |
| L95 | The base level means the level, which is exceeded in 95% of the measurement period. |
| Leq | The energy equivalent level expresses the level, which - held constant over the whole period - results in the same energy as the original variable sound levels. The neighboured building site of the central heating plant must not exceed 65 db(A) over the loudest 30 minutes per day, if obeying legislative and governmental requirements. The formula used to compute the energy equivalent level is: Leq=q/log(2)*log(1/(∑ ti) * (∑ (10(Li*log(2)/q)*ti))) where q=3 ... following international standards and national ÖAL guidelines to assess sounds log ... Logarithm to basis 10 ti ... time period of each single measurement Li ... single measured sound level |
| Lmax | The maximum level is the highest level measured during measurement time. The building site must not exceed 80 db(A) at any time or period of time according to national law and governmental requirements. |
| Lmin | The minimum level is the lowest level measured in the time interval |
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