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Model407780‐ENv2.31/14

Sound Pressure Measurements (SPL)

In SPL mode the display shows readings of the sound pressure level.

1. Turn the meter on by pressing the green on/off button.

2. Select the SPL mode by pressing the Leq SEL SPL button until SPL appears on the LCD.

3. Select the desired Frequency Weighting as needed (A or C).

Change the Frequency Weighting by pressing the A/C button. The 'A' or 'C' icon will display on

the right-hand area of the LCD.

Note: With ‘A’ weighting selected, the meter responds like the human ear. ‘A’ weighting is

commonly used for environmental measurements, OSHA regulatory testing, law enforcement,

and workplace design. Select ‘C’ weighting for flat response measurements. ‘C’ weighting is

typically used for the sound level analysis of machines, engines, etc. Most hearing

conservation related testing is performed using 'A' Weighting.

4. Select the desired Response Time as needed (Fast, Slow or Impulse).

Change the Response Time by pressing the 'FAST/SLOW/IMPULSE' button. The 'FAST' 'SLOW'

or IMP icon will display.

Note: Select FAST to capture noises that occur very quickly. In FAST mode, the meter

responds in 125ms. Select the SLOW Mode (meter responds in 1s) to monitor a sound

source that has a reasonably consistent noise level or to average quickly changing levels. In

IMPULSE mode the meter responds in 35ms and is used to capture the rms value of

repetitive impulse noises. Selection of Fast or Slow is determined by the application and any

directives or standards related to that application. Most hearing conservation related testing is

performed using a SLOW Response Time setting.

5. Hold the instrument comfortably in hand and away from your body or position it on a tripod. Point

the microphone toward the noise source, the sound pressure level will be displayed on the

meter’s LCD display.

MIN/MAX Function

Press the MAX MIN INST button to begin capturing the, Maximum (MAX) OR Minimum (MIN) sound

values. The display will indicate the MAX or MIN value (depending on which is selected) captured

since the MAX/MIN button was pressed. Press and hold the

MAX MIN INST button to return to the instantaneous reading mode

Note:

When the meter is measuring the following buttons cannot be used:

• FAST, SLOW, IMPULSE

• A/C Weighting

• INTEG TIME

• RECORD ERASE

• DATE/TIME

• UP/DOWN Arrow keys

Extech Instruments 407780 User Manual

Questions and Answers: