Sound level meter - Frequently Asked Questions

■ calibration of the sound level meter

There are two methods for calibration a sound level meter: using an acoustic calibration such as a pistonphone (sold separately), or using an internal calibration signal.

calibration using an acoustic calibration

This method involves acoustic calibration using an acoustic calibration such as a pistonphone. Please calibration that the acoustic calibration (see below) must be purchased separately.

• SC-3100… Frequency: 250Hz (typical value) / Sound pressure level: 124dB (typical value)
• SC-2120 … Frequency: 1kHz (typical value) / Sound pressure level: 94dB (typical value)

【Note】

The sound pressure level generated by calibration has a value specific to calibration. Therefore, please be sure to check the output sound pressure level of calibration before performing calibration.

calibration procedure using an acoustic calibration

This section describes calibration procedure using calibration acoustic calibrator, with the SC-3100 sound calibration as an example.

1. Attach the acoustic calibration to the microphone of the sound level meter.
   At this time, insert the microphone slowly into the input slot of the acoustic calibration without applying excessive force.

   

2. Turn on the acoustic calibration.
3. After switching the sound level meter's power ON, set the measurement conditions as follows:

   a	Measurement items	Lc or Lp
   b	Frequency Correction Characteristics	C or FLAT
   c	Dynamic characteristics	FAST or SLOW
   d	Level range	Set to the 60-130dB range. (When using SC-2120, the range is 30-100dB)

   
4. The sound level meter reading is calibration to the sound pressure level generated by the calibration.
   The indicated value is adjusted by turning the calibration gain adjustment volume (CAL) located on the side of the sound level meter using the included adjustment screwdriver.

calibration using internal calibration signals

calibration using the internal calibration signal is a method of electrically calibration the sound level meter itself, assuming that the microphone sensitivity remains constant. When the internal calibration signal is turned ON, a calibration signal (frequency 1kHz) is output from the output terminal. This calibration signal is equal to -6dB relative to the full scale of each level range. Furthermore, the calibration signal output from the output terminal can also be used as a level calibration signal for peripheral devices connected to the sound level meter.

【Note】

calibration signals cannot be used while calculations are in progress. Please be aware of this.

calibration procedure using internal calibration signals

1. After switching the sound level meter power ON, set the measurement conditions as follows.

   a	Measurement items	Lc or Lp
   b	Frequency Correction Characteristics	C or FLAT
   c	Dynamic characteristics	FAST or SLOW

2. Turn on the internal calibration signal.
   Pressing the panel switch [CAL] outputs an internal calibration signal, and the CAL mark lights up on the LCD screen.
   Now, please confirm that the displayed value is 6dB less than the upper limit of the level range display.
3. Adjust the displayed value so that it is 6 dB lower than the upper limit of the level range display.
   Using the included adjustment screwdriver, rotate the calibration gain adjustment volume (CAL) located on the side of the sound level meter to adjust it so that it reaches 84.0 dB in the 90 dB range (the upper limit of the level range display is 90 dB).