Sound Level Meter Type 2255 –
Instruction Manual
Page 4 of 133
3.4 Wi-Fi and Bluetooth During Tests ....................................................... 40
3.5 Mounting f or Acoustical Tests............................................................. 40
3.6 Periodic Testing of Acoustical Frequency Responses .......................... 41
3.7 Mounting f or Mechanical Vibrations Tests ........................................... 41
3.8 Testing 1/1-octave Band and 1/3-octave Band Filters........................... 41
3.9 EMC Test Procedures........................................................................ 42
3.9.1 Signal So urces f or Immunity Test .............................................. 42
3.9.2 Ref erenc e Orientatio n .............................................................. 42
3.9.3 Securing of Cables during EMC Test ......................................... 43
3.9.4 Accessories Included in EMC Test ............................................ 43
3.9.5 Normal Mode of Operation during EMC Test.............................. 43
Chapter 4 Specif ications............................................................................... 46
4.1 Specif ications.................................................................................... 46
4.2 Standards ......................................................................................... 46
4.3 Ref erenc e Environment al Conditions .................................................. 46
4.4 Ref erenc e Conditions for Acoustic Calibration ..................................... 47
4.5 Microphone....................................................................................... 47
4.6 Frequency Responses ....................................................................... 48
4.6.1 Electrical Frequency Responses ............................................... 48
4.6.2 Typical Low-f requency Responses ............................................ 49
4.6.3 Acoustical Frequency Responses ............................................. 50
4.6.4 Free-f ield Frequency Respo nses .............................................. 50
4.6.5 D iff use-f ield Frequency Responses ........................................... 52
4.6.6 Free-f ield Frequency Responses f or Dif f use-f ield
Calibrated Instruments ............................................................. 52
4.7 Directional Responses ....................................................................... 53
4.8 Self -generated Noise ......................................................................... 64
4.8.1 Maximum Broadband Self -generat ed Noise............................... 64
4.8.2 Typical Broadband Self -generated Noise................................... 64
4.8.3 Typical Self-generated Noise Spectra........................................ 65
4.9 Measuring Ranges ............................................................................ 66
4.9.1 Maximum Sound Level ............................................................. 66
4.9.2 Total Range............................................................................. 66
4.9.3 Primary Indicator Range ........................................................... 66
4.9.4 Indicator Range ....................................................................... 67
4.9.5 Linearity Range........................................................................ 67
4.9.6 Pulse Range............................................................................ 68
4.9.7 Linear Operating Range ........................................................... 68
4.9.8 Peak C Range ......................................................................... 68
4.10 Detectors .......................................................................................... 69
4.10.1 Exponential Averaging.............................................................. 69
4.10.2 Linear Averaging...................................................................... 70
4.10.3 Peak ....................................................................................... 70
4.11 Spectrum Analysis............................................................................. 70
4.11.1 1/1- octave Band Centre Frequencies ....................................... 70
4.11.2 1/3-octave Band Centre Frequencies ........................................ 71
4.11.3 Linear Operating Range ........................................................... 72
4.11.4 Measurement Range................................................................ 72
4.11.5 Octave Band Time Constants ................................................... 73
4.12 Inf luence f rom the Operating Environment .......................................... 73
4.12.1 Environmental Stabilisation Time .............................................. 73
4.12.2 Temperat ure ............................................................................ 73
4.12.3 Humidity.................................................................................. 73
4.12.4 Vibration.................................................................................. 73
4.13 Wirel ess Interf ace to the Sound Level Meter ....................................... 74
4.13.1 Bluetooth................................................................................. 74
