Sound level meter - Frequently Asked Questions

To obtain more accurate measurements, we recommend calibration the sound level meter's microphone regularly. There are two methods for calibration a sound level meter: using the oscillator built into the sound level meter, or using a separately sold acoustic calibration (SC-3100).

1. calibration procedure using the built-in oscillator

calibration using an internal oscillator is a method of electrically calibration the sound level meter itself by utilizing the fact that the microphone's sensitivity remains constant. When the internal calibration signal is turned ON with the level range set to 30-90 dB, a calibration signal (frequency 1 kHz) is output from the output terminal. This calibration signal is equal to -6 dB relative to the full scale of each level range (-16 dB for wide range). The calibration signal output from the output terminal can also be used as a level calibration signal for each device connected to the sound level meter.

◆Operation

• Set the measurement conditions for the sound level meter for calibration.
  Measurement mode: INST (Panel switch [Tact Max])
  Measurement range: Reference range (30-90 dB) (Level range switch [△・▽])
  
• Turn on calibration signal.
  Pressing the panel switch [CAL] turns on calibration signal, and the marker moves to calibration value setting position.
  
• Adjust the displayed value to 84.0 dB.
  Using the marker position on the bar indicator as a guide, turn the gain adjustment knob for the “calibration” using the included adjustment screwdriver until the displayed value reaches 84.0 dB. Please note that you should not turn or press the gain adjustment knob for the “calibration” with excessive force. Doing so may cause a malfunction.
  
• Turn off calibration signal.
  After calibration is complete, pressing the panel switch [CAL] again will turn off calibration signal.

2. calibration procedure using an acoustic calibration

This method involves acoustic calibration using an acoustic calibration. If you wish to perform calibration using an acoustic calibration, please purchase the separately sold acoustic calibration (Sound Calibrator SC-3100).

◆Operation

• Set the measurement conditions for the sound level meter as follows for calibration.

  display screen	Standard screen (Panel switch [LIST])
  Display	: LP display (Panel switch [LP / Leq …])
  Frequency correction	: FLAT display is P (Panel switch [A/C/FLAT])
  Measurement mode	INST (Panel Switch [Tact Max])
  SC-3100	Calibration frequency: 250Hz (typical value)
  Sound pressure level	: 124 dB (typical value)

• Place the sound level meter's microphone into the acoustic calibration.
  Insert the microphone into the sound calibrator's input.
  
• Turn on the acoustic calibration.
  
• Set the measurement range so that calibration level is at its maximum position without exceeding the full scale.
  
• Set calibration value to calibration reference sound pressure level.
  Use the included adjustment screwdriver to turn calibration gain adjustment volume so that calibration value matches calibration reference sound pressure level of the acoustic calibration. Do not forcefully turn or push the calibration gain adjustment volume, as this may cause damage.

<Memo>
Each acoustic calibration has its own unique calibration reference sound pressure level. Before performing calibration, please check the calibration reference sound pressure level of your acoustic calibration by referring to the inspection report included with the calibration.

3. Proofreading calibration

We offer commissioned calibration (for a fee) upon pickup of the device. A test report will be provided, and upon request, a traceability diagram (for a fee) and a calibration certificate (for a fee) will be included.

4. Certificate of Examination

After receiving the equipment for inspection, we are contracted to perform inspections at public institutions. The "certificate of verification" is issued in accordance with the Measurement Law and is affixed with a sticker valid for 5 years. For more information on the certificate of verification, please refer to "What is a sound level meter?" in the "What's New Ono Sokki Report" section.