Noise dB to dBA Calculation_Gan Chun Chet.pptx

How do you add the noise level together? Note that there are 10 frequencies...

In this presentation, the method to compute (formula and procedure in Excel) the noise level from dB to dB(A), is shared herein.

1. Noise dB to dB(A) Calculation The Formula and Procedure Gan Chun Chet (Mr.) MSc in Operations Management 1997 University of Manchester Institute of Science and Technology UMIST, United Kingdom BEng (Hons) in Mechanical Engineering 1996 University of Manchester, United Kingdom

2. dB to dBA : A-Weighting Corrections (1) Noise Level Frequency (Hz) 31.5 63 125 250 500 1kHz 2kHz 4kHz 8kHz 16kHz Level (dB) 70.9 78.4 83.3 87.6 87.3 93.5 93.8 97 99.9 98.2 Next, Adding A-Weighting Corrections Frequency (Hz) 31.5 63 125 250 500 1kHz 2kHz 4kHz 8kHz 16kHz A-Weighting Correction (dB) -39.4 -26.2 -16.1 -8.6 -3.2 1.2 1 -1.1 -6.6 Result (dB) 31.5 52.2 67.2 79 84.1 93.5 95 98 98.8 91.6 Adding each (respective frequency/components), raw data, with A-weighting corrections Measured raw data, in decibel dB The result, by adding each (respective frequency/components), raw data, with A-weighting corrections Respective frequency of each component

3. dB to dBA : A-Weighting Corrections (2) Example of Calculation:- At 2kHz, measured data is 93.8 dB By adding the A-weighting at this frequency, which is 1.2 dB, the result in dB for this particular frequency shall be 95 dB. However, it is impossible just to sum all the readings for respective frequency and averaging the raw data to obtain a result in decibel dB. Instead, a procedure to sum all these readings is stipulated in the next slide.

4. o A B C D E F G H I J K 1 Frequency (Hz) 31.5 63 125 250 500 1kHz 2kHz 4kHz 8kHz 16kHz 2 Result (dB) 31.5 52.2 67.2 79 84.1 93.5 95 98 98.8 91.6 3 4 Details 5 A = 10^[dB]/10 - 165958.69 5248074.6 79432823 257039578 2.239E+09 3.162E+09 6.31E+09 7.586E+09 1.445E+09 6 C = 10log(A+B) ; dB(A) - 52.236808 67.336342 79.28643 85.338837 94.117222 97.591302 100.81076 102.93102 103.23946 7 B = 10^[dB]/10 1412.5375 167371.23 5415445.8 84848269 341887848 2.581E+09 5.743E+09 1.205E+10 1.964E+10 - dB to dBA : The Formula and Procedure (1) 1.1 Divide the ‘result’ in dB by 10 1.2 Then anti-log the ‘value’, which means calculate 10 to the power of the ‘value’. This will give you the noise intensity only at this particular frequency. [derived from =   3.1 Thereafter add the current noise intensity and preceding noise intensity, = = 3.2 Log (base 10) the added noise intensity and multiply by 10, in accordance to the formula to calculate Intensity Level IL. = 10 log (   Calculations (Steps):- 1.1 : 31.5/10 = 3.15 (31.5Hz) 1.2 : = 1.412 x 2.1 : 52.2 /10 = 5.22 (63 Hz) 2.2 : = 1.659 x 3.1 : 1.412 x + 1.659 x = 1.673 x 3.2 : 10 * (1.673 x = 52.23 dB   2.1, 2.2 Then calculate the next noise intensity of the subsequent frequency by repeating the same procedure, 1.1 and 1.2 4.1 Repeat until the end for subsequent frequency.

5. dB to dBA : The Formula and Procedure (2) o A B C D 1 Frequency (Hz) 31.5 63 125 2 Result (dB) “B2” “C2” D2 3 4 Details (formula) :- 5 A = 10^[dB]/10 - “C5” = POWER(10, "C2"/10) “D5” = POWER(10, "D2"/10) 6 C = 10log(a+b) ; dB(A) - ”C6” = 10*LOG(("B7"+"C5"),10) ”D6” = 10*LOG(("C7"+"D5"),10) 7 B = 10^[dB]/10 “B7” = POWER(10, "B2"/10) “C7” = POWER(10, "C6"/10) … “D7” = POWER(10, "D6"/10) Formula, in Excel, as shown below