Low Frequency Noise – the XL2 now offers a valuable toolbox for effective assessment
The Data Explorer PC software for the XL2 Sound Level Meter now includes a series of professional tools for detailed analysis of low-frequency noise (LFN). The graphical representation of time varying frequency components offers an efficient process for identifying the presence and level of LFN. Also the associated high quality audio recording supports further correlation with the objective measurement data.
The new features are particularly useful in the calculation of immission levels which is defined as the cumulative noise energy to which an individual is exposed over time. Exposure to low-frequency noise over extended periods can lead to a range of health problems including cardio vascular disease, insomnia and depression. The sources of low frequency noise can often be attributed to electricity sub stations, chiller plants and incinerators with continuous noise at frequencies below 200 Hz.
XL2 Sound Level Meter records all Data
Measuring LFN requires a class 1 sound level meter, such as the XL2 in combination with the M2230 measurement microphone. The XL2 stores all measured levels and audio recordings continuously on the removable SD card. After completion of the measurement, the data can be easily imported into the Data Explorer software for comprehensive analysis of the low-frequency characteristics and calculation of the noise immission levels.
Calculation of Broadband Level Difference LCeq-LAeq
The XL2 Sound Level Meter already calculates and displays the live broadband level difference LCeq-LAeq onsite during the recording. When the measurement is completed, the Data Explorer software graphically displays this difference simultaneously over the entire measurement period. A difference exceeding locally defined dB limits is a clear indication that there is excessive energy in the low-frequency range of the spectrum. A more detailed analysis can then be undertaken by examining the individual one-third octave bands over time.
Examine On/Off Pattern in one-third Octave Bands
Select one or more, or a range of one-third octave bands for display against time. For example, choose the range 8 - 125 Hz to see how much energy was produced in these frequencies and whether an on/off pattern can be identified which corresponds with the operational behavior of near-by machinery. The extensive analysis capabilities of the Data Explorer also allow the calculation of level statistics on these individual bands.
Correlation with Audio Data
The correlation of the objective measurements with the subjective sound recording further validates the analysis. Therefore the class 1 XL2 Sound Level Meter in combination with the Data Explorer software provides a professional solution for the everyday demands of acousticians assessing environmental noise.
The new low-frequency analysis features are part of the Data Explorer V1.30 release, which is now available for download, free of charge to all licensed users. An XL2 with the optional Extended Acoustic Pack provides onsite the broadband level difference calculation LCeq-LAeq along with the linear high quality sound recording capability so useful for the subjective assessment.