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Rion NL-42 Technical Notes

Sound level meter
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TECHNICAL NOTES

Sound Level Meter

NL-42 / NL-52
3-20-41 Higashimotomachi, Kokubunji, Tokyo 185-8533, Japan
http://www.rion.co.jp/english/

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Summary of Contents for Rion NL-42

  • Page 1: Technical Notes

    TECHNICAL NOTES Sound Level Meter NL-42 / NL-52 3-20-41 Higashimotomachi, Kokubunji, Tokyo 185-8533, Japan http://www.rion.co.jp/english/...

  • Page 3: Organization Of The Nl-42/Nl-52 Documentation

    Serial Interface Manual Describes communication with a computer, using the serial interface built into the Sound Level Meter NL-42/NL-52. The manual covers the com- munication protocol, use of control commands for the sound level meter, format of data output by the sound level meter, and other topics.

  • Page 4: Table Of Contents

    Contents Organization of the NL-42/NL-52 documentation ......i Microphone ..................1 Construction and operation principle .........1 Thermal characteristics ..............2 Humidity characteristics ............3 Specifi cations of microphone UC-59 ..........4 Specifi cations of microphone UC-52 ..........5 Preamplifi er ..................6 Preamplifi er Requirement ............6 Preamplifi er Specifi cations ............6...
  • Page 5 The greatest susceptibility confi guration for radio frequency fi elds ...............36 Statement of conforming to the basic statement ......36 Adjustment data for sound calibrator ........37 The lower and upper limits of the linear operating range ..38 Directional Characteristics ............39 Random incidence response .............43...

  • Page 7: Microphone

    Measurements of sound pressure level can be carried out with a variety of microphone types. The sound level meter NL-52 employs the prepolarized condenser microphone UC-59 (NL-42 employs UC-52) that is compact and delivers stable and reliable response. Construction and operation principle...

  • Page 8: Thermal Characteristics

    Microphone Thermal characteristics The thermal characteristics of a microphone indicate how sensitivity changes at various temperatures. The diagrams below show the thermal characteristics of the microphone UC-59 and UC-52. -0.1 -0.2 -0.3 -0.4 -0.5 Temperature (°C) Thermal characteristics of UC-59 (at 250 Hz) -0.1 -0.2 -0.3...

  • Page 9: Humidity Characteristics

    Microphone Humidity characteristics The humidity characteristics of a microphone indicate how sensitivity changes at various humidity levels. The diagrams below show the microphone UC-59 and UC-52. -0.1 -0.2 -0.3 -0.4 -0.5 Relative humidity (%) Humidity characteristics of UC-59 (at 250 Hz) -0.1 -0.2 -0.3...

  • Page 10: Specifi Cations Of Microphone Uc-59

    Microphone Specifi cations of microphone UC-59 Model: UC-59 Nominal diameter: 1/2 inch Sensitivity: -27 dB ±2 dB (re. 1 V/Pa)* Frequency response: 10 to 20000 Hz Capacitance: 13 pF ±1.5 pF Temperature dependent sensitivity level fl uctuation: ±0.35 dB max. from -10 to +50ºC referenced to 23ºC (at 1 kHz) ±0.5 dB max.

  • Page 11: Specifi Cations Of Microphone Uc-52

    Microphone Specifi cations of microphone UC-52 Model: UC-52 Nominal diameter: 1/2 inch Sensitivity: -33 dB (re. 1 V/Pa)* Frequency response: 20 to 8000 Hz Capacitance: 19 pF Diaphragm type: Titan alloy fi lm Temperature coeffi cient: -0.008 dB / ºC (at 250 Hz) Humidity-dependent sensitivity change: 0.1 dB or less (at 250 Hz, 95%RH or below, no condensation)

  • Page 12: Preamplifi Er

    For the above reasons, a preamplifi er of high input impedance is connected directly after the microphone, to provide a low-impedance output signal. Preamplifi er Specifi cations Model name: NH-24 (NL-42) NH-25 (NL-52) Input impedance: Approx. 3 GΩ // 9 pF Approx.

  • Page 13: Infl Uence Of Microphone Extension Cable

    Infl uence of Microphone Extension Cable When the output of the microphone/preamplifi er is routed through an exten- sion cable, certain limitations regarding measurable sound pressure level and frequency range will apply. This is due to the infl uence of the cable capaci- tance.

  • Page 14: Frequency Weighting Network

    Frequency Weighting Network The NL-42/NL-52 provides frequency weightings A, C and Z. The electri- cal characteristics of the weighting network at AC output connector are as shown below. Z weighting Z weighting A weighting C weighting C weighting A weighting...

  • Page 15: Rms Detection Circuit And Time Weighting

    T is performed. The result is divided by T and the square root is extracted. The circuit confi guration for performing the above mathematical operation looks as follows. The NL-42/NL-52 uses digital processing to determine the rms value. E(rms) Second power...
  • Page 16 RMS Detection Circuit and Time Weighting During sound level measurements, the level often fl uctuates drastically, which would make it diffi cult to evaluate readings if some kind of averaging is not applied. Sound level meters therefore provide the capability for index weighting (index averaging) using the rms circuit.
  • Page 17 RMS Detection Circuit and Time Weighting Time weightings and time constant Time constant Time Weighting Decay time Rise time 125 msec F (Fast) 125 msec S (Slow) 35 msec I (Impulse) 1.5 sec The time weighting network of the sound level meter performs index averaging on the square of the sound pressure signal.

  • Page 18: Measurement Functions

    In sound pressure level meter NL-42/NL-52, the digital processing to deter- mine L is carried out according to the following equation. ½ 20 log (i ) Number of samples In NL-42/NL-52, the sampling interval is 20.8 μs (48000 samples per sec- ond).

  • Page 19: Lae (Sound Exposure Level)

    Reference sound pressure (20 μPa) In NL-42/NL-52, the digital processing to determined L is carried out according to the following equation. (i ) 10 log Number of samples per second In NL-42/NL-52, the sampling interval is 20.8 μs (48000 samples per sec- ond).

  • Page 20: L N (Percentile Sound Level)

    (percentile sound level) is the sound level which was N percent or more of the measurement time. The NL-42/NL-52 allows the user to select fi ve values for N (from 1 to 99, in 1 steps). The sampling interval for L...

  • Page 21: L Atm5 (Takt-Max Sound Level)

    Measurement Functions (takt-max sound level) Atm5 For the duration of the measurement, the maximum level within a 5-second interval is sampled and the power average is determined. L is calculated according to the following equation. Lm/10 10 log Maximum level within interval (5 seconds) Number of samples The number of samples is determine according to the following equation.

  • Page 22: Infl Uence Of Background Noise

    Infl uence of Background Noise When measuring a certain sound in a certain location, all other sounds present at that location except the measurement target sound are background noise (also called ambient noise or dark noise). Since the sound level meter will display the combination of target sound and background noise, the amount of background noise must be taken into consideration when determining the level of the target sound.

  • Page 23: Description For Iec 61672-1

    Relative humidity:50% Performance specifi cations General 5.1.4 Confi guration & normal 9.2.1 b) Confi guration Confi guration mode of operation • NL-52 • NL-42 • WS-10 • WS-10 Controls and Functions, Controls and Functions, Preparations Preparations 5.1.6 Models of microphone 9.2.1 c)
  • Page 24 Initial time interval after 9.2.5 e) Less than 90 seconds Less than 90 seconds switching on power Adjustment to indicated levels 5.2.1 Model of 9.2.4 a) NC-74 (RION) NC-74 (RION) sound calibrator(s) 5.2.3 Procedure for calibration 9.2.4 c) Calibration Calibration &...
  • Page 25 Description for IEC 61672-1 Remark Standard Description paragraph also NL-52 NL-42 5.5.11 How to test level linearity 9.3 k) if display range < linear- ity range Self generated noise 5.6.1 Self-noise at the more 9.2.5 o) Maximum value Maximum value sensitive ranges (includ- 9.3 h)
  • Page 26 Description for IEC 61672-1 Remark Standard Description paragraph also NL-52 NL-42 5.15.4 Description of the dis- 9.2.2 a) N/A played quantities 5.15.5 Statement of the display 9.2.2 g) 1 second 1 second update rate 5.15.6 Time interval for comple- 9.2.5 f) Less than 1 second...
  • Page 27 Description for IEC 61672-1 Remark Standard Description paragraph also NL-52 NL-42 5.18.2 Operating mode or high- 9.3 n) Operation mode: normal Operation mode: normal est radio frequency emis- operation operation sions Connection pattern: Connection pattern: AC adapter NC-98 AC adapter NC-98...
  • Page 28 Effect of optional acces- 9.2.6 a) Infl uence of WS-10 on Infl uence of WS-10 on sories (windscreen) acoustic performance of acoustic performance of NL-52/NL-42 (Fig. 10) NL-52/NL-42 (Fig. 10) Statement of conformance Compliant with IEC Compliant with IEC with optional accessories...
  • Page 29 Description for IEC 61672-1 Remark Standard Description paragraph also NL-52 NL-42 9.2.2 g) Description of the display 5.15. 2 - Refer to 5.15.2-3-4-5 Refer to 5.15.2-3-4-5 and update rates 3-4-5 9.2.2 h) Total range of A- weighted 5.1.12 Refer to 5.1.12 Refer to 5.1.12...
  • Page 30 Description for IEC 61672-1 Remark Standard Description paragraph also NL-52 NL-42 9.2.5 b) Procedure to measure 5.1.6 Refer to 5.1.6 Refer to 5.1.6 sound, 5.2.4 Refer to 5.2.4 Refer to 5.2.4 Infl uence of the instrument 5.2.5 Refer to 5.2.5 Refer to 5.2.5...
  • Page 31 Description for IEC 61672-1 Remark Standard Description paragraph also NL-52 NL-42 9.2.6 b) Corrections for microphone Refer to 7.1 Refer to 7.1 cable 9.2.6 c) Use of bandpass fi lters Refer to 7.4 Refer to 7.4 9.2.6 d) Connection of auxiliary Refer to 7.5...
  • Page 32 Description for IEC 61672-1 Remark Standard Description paragraph also NL-52 NL-42 9.3 j) Maximum and minimum 5.20.2 Refer to 5.20.2 Refer to 5.20.2 power supply voltage 9.3 k) How to test level linearity 5.5.11 Refer to 5.5.11 Refer to 5.5.11 if display range <...

  • Page 33: Iec 61672-1 (Jis C 1509-1) Frequency Response

    Description for IEC 61672-1 IEC 61672-1 (JIS C 1509-1) frequency response Tab. 1 IEC 61672-1 (JIS C 1509-1) frequency response UC-59 UC-52 NL-42/52 NL-42/52 Windscreen Total Windscreen Nominal Exact Frequency Frequency Frequency Electrical (WS-10) (WS-10) Expanded Frequency Frequency Response Response...

  • Page 34: Reference Incidence Direction And Reference Point Position

    Description for IEC 61672-1 Reference incidence direction and reference point position Reference direction of incidence Reference point position Center of diaphragm plane Fig. 1 Reference incidence direction and reference point position...

  • Page 35: Frequency Response

    Description for IEC 61672-1 Frequency response The frequency response of a sound fi eld microphone is expressed as the fre- quency response in the reference direction of incidence (0º). The diagram below shows an example for the frequency response of the microphone UC-59 and UC-52.

  • Page 36: Infl Uence Of Body Refl Ection

    Description for IEC 61672-1 Infl uence of body refl ection The NL-52/NL-42 is designed to minimize refl ections caused by the body of the unit. The chart below shows the infl uence on the measurement. 100000 1000 10000 Frequency (Hz)

  • Page 37: Acoustical Infl Uence Of Operator

    Description for IEC 61672-1 Acoustical infl uence of operator 10 k 20 k Frequency (Hz) Fig. 5 Acoustical infl uence of operator (the distance from the top of the microphone to the operator is approx. 40 cm) 10 k 20 k Frequency (Hz) Fig.

  • Page 38: Reduction Of Wind Noise By Windscreen

    Description for IEC 61672-1 Reduction of wind noise by windscreen During outdoor measurements or measurement of ventilation devices, wind noise can falsify measurement results. To counter such problems, the supplied windscreen WS-10 should be mounted on the microphone. The characteristics of the WS-10 are shown below.
  • Page 39 Description for IEC 61672-1 -1.0 500 1 k 5 k 10 k 50 k Frequency (Hz) Fig. 10 Infl uence of windscreen WS-10 on acoustical properties of microphone (referred to microphone response without windscreen) -1.0 -2.0 -3.0 Windscreen attached, with no correction for it -4.0 Windscreen attached, with correction for it -5.0...

  • Page 40: Effect Of All-Weather Windscreen Ws-15

    Description for IEC 61672-1 Effect of All-Weather Windscreen WS-15 The windscreen WS-15 not only reduces measurement errors due to wind noise, it also protects the microphone from rain. The WS-15 characteristics are shown below. Microphone only Microphone only With WS-15 With WS-15 Wind velocity (m/s) Wind velocity (m/s)

  • Page 41: Effect Of Rain-Protection Windscreen Ws-16

    Description for IEC 61672-1 Effect of Rain-protection Windscreen WS-16 The windscreen WS-16 not only reduces measurement errors due to wind noise, it also protects the microphone from rain. The WS-16 characteristics are shown below. Microphone only Microphone only With WS-16 With WS-16 wind velocity (m/s) wind velocity (m/s)

  • Page 42: The Greatest Susceptibility Configuration For Radio Frequency Fi Elds

    Fig. 16 The greatest susceptibility confi guration for radio frequency fi elds Statement of conforming to the basic statement Tab. 2 Statement of conforming to the basic statement NL-52 NL-42 The specifi cation of IEC The specifi cation of IEC Immunity (AC power fre-...

  • Page 43: Adjustment Data For Sound Calibrator

    Description for IEC 61672-1 Adjustment data for sound calibrator Tab. 3 Adjustment data for sound calibrator NL-52 NL-42 Frequency (Hz) Correction (dB) Correction (dB) 31.5 1000 2000 4000 8000 12500 16000...

  • Page 44: The Lower And Upper Limits Of The Linear Operating Range

    Description for IEC 61672-1 The lower and upper limits of the linear operating range Tab. 4 The lower and upper limits of the linear operating range A weighting 31.5 Hz 1 kHz 4 kHz 8 kHz 12.5 kHz Upper 98.0 138.0 138.0 136.0...

  • Page 45: Directional Characteristics

    The directional characteristics of a microphone is a measure of its differing sensitivity for sound waves arriving from various angles. Since the prepolar- ized condenser microphone used in the NL-52/NL-42 is a pressure-sensitive type, it should be equally sensitive in all directions. However, refraction and cavity effects cause a certain microphone directional response at high frequencies.
  • Page 46 Description for IEC 61672-1 Tab. 5 Directional Characteristics of NL-52/NL-42 (Rotated horizontal) Frequency (Hz) Angle 12.5k ° 0.00 0.00 0.00 0.00 0.00 ° 0.12 -0.02 0.05 -0.07 -0.20 ° 0.09 -0.09 0.01 -0.67 -0.79 ° 0.17 -0.16 -0.13 -0.94 -1.17 °...
  • Page 47 280° 80° -20dB 270° 90° 260° 100° 250° 110° 1 kHz 240° 120° 2 kHz 230° 130° 4 kHz 220° 140° 8 kHz 210° 150° 12.5 kHz 200° 160° 190° 170° 180° Fig. 18 Directional Characteristics of NL-52/NL-42 (Rotated vertical)
  • Page 48 Description for IEC 61672-1 Tab. 6 Directional Characteristics of NL-52/NL-42 (Rotated vertical) Frequency (Hz) Angle 12.5k ° 0.00 0.00 0.00 0.00 0.00 ° 0.06 0.01 0.06 -0.03 -0.20 ° 0.05 -0.04 0.15 -0.46 -0.42 ° 0.08 -0.11 0.06 -0.64 -1.06 °...

  • Page 49: Random Incidence Response

    Description for IEC 61672-1 Random incidence response (dB) 1000 10000 100000 Frequency (Hz) Fig. 19 Random incidence response...
  • Page 50 No. 55753 13-06...

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