SPL / Leq Meter Component [BETA]

The SPL / Leq meter provides the ability to measure sound loudness using two different methods. The SPL meter is an exponentially averaging sound level meter with an integration time-constant, referred to as the time-weighting. The Leq meter is a continuous equivalent sound level meter of the integrating-averaging type with an integration time.

Note: This is a BETA component. Though it is functional, it is not feature complete and is subject to change.

Input

Usually connected to an analog mic/line input card which in turn is connected to a (measurement) microphone.

Weighted Output

The output is visual (looking at the level readings in the control panel). In addition you can log the readings by using a control script. The frequency-weighted filter audio output is also available.

Tip: For additional properties not listed, refer to the Properties Panel help topic for more information.

SPL/Leq Meter [BETA] Properties

Meter Type

Exponentially averaging SPL meter or Integrating-averaging Leq meter.

Frequency Weighting

  • Linear or flat frequency weighting means that the input signal is not filtered before the level is calculated.
  • An A-weighting filter typically emphasizes frequencies where the human ear is most sensitive, around 3–6 kHz. In addition, the filter attenuates frequencies where the ear is less sensitive, that is, very high and very low frequencies.
  • A C-weighting filter includes more of the low frequencies, and is used at higher sound levels where the lower frequencies can be heard better by the human ear.

Level Range

The meter's useful range is 100dB. Depending on the nominal expected sound pressure level, this range can be adjusted from 0 - 100 dB to 40 - 140 dB.

The meter is calibrated using pink noise. This source can be external to Q-SYS, or can be generated by Q-SYS using the Pink Noise generator component and played out through the system.

  1. Set the pink noise at a nominal level and wait at least twice the Time Weighting (for the SPL meter) or the Leq Time (for the Leq meter) for the meter value to settle.
  2. Use an external, calibrated, SPL meter to measure the level of the pink noise.
  3. Ensure that both external and Q-SYS meters use the same Time and Frequency Weighting!
  4. Enter the SPL level using the Reference Level control.
  5. Click the Calibrate button and verify that both external and Q-SYS meters show the same level. The Q-SYS meter is calibrated.

Note: Depending on the Frequency Weighting setting, the Level units of measure will change. Linear = dB, ANSI S1.42 A = dBA, ANSI S1.42 C = dBC. In this topic, all units are listed as dB regardless of the Frequency Weighting setting.

The Meter Type in the Properties must be set to SPL to see the following controls.

Sound Pressure Level (dB)

Displays the current level.

Capture

Click this button to capture the current level reading.

Reference Level (dBA)

The Reference Level is used to calibrate the meter. Set this level to the level measured by an external, calibrated, SPL meter. Refer to the Calibration Procedure for details.

Calibrate

After setting the Reference Level, click this button to calibrate the meter.

Refer to the Calibration Procedure for details.

Time Weighting (seconds)

This control determines the meter's response time to changing levels. There are two standard weightings, Slow (1s) and Fast (125ms).

Max Hold Time (seconds)

Sets the time interval to reset the maximum level.

Infinite Max Hold

When on, this button causes the Max Hold Time to be ignored. The maximum level is held until manually reset.

Reset Max

Click this button to reset the maximum level.

Max SPL (dBA)

Keeps track of the maximum SPL level over time.

The Meter Type in the Properties must be set to Leq to see the following controls.

Equivalent Continuous Sound Level (dBA)

This graph shows a time chart of the most recent levels.

Capture

Click this button to capture the current level reading.

Reference Level (dBA)

The Reference Level is used to calibrate the meter. Set this level to the level measured by an external, calibrated, SPL meter. Refer to the Calibration Procedure for details.

Calibrate

After setting the Reference Level, click this button to calibrate the meter.

Refer to the Calibration Procedure for details.

Leq Time (seconds)

Determines the meter's time interval over which the level is integrated and averaged.

Reset Max

Click this button to reset the maximum level.

Max Leq (dBA)

Tracks the maximum Leq level over time.

Max Leq is on infinite hold, and can only be reset manually with the Reset Max button.

Leq (dBA)

Displays the current level.

The following Control Pins are common to both SPL and Leq meter types.

Pin Name

Value

String

Position

Pins Available

Calibrate Level

(Momentary)

0

1

false

true

0

1

Input / Output

Capture Level

(Momentary)

0

1

false

true

0

1

 Input / Output

Captured Level

dB

0 to 140

0 dB to 120 dB

0.00 to 1.00

 Output

External Reference Level

dB

0 to 140

0 dB to 140 dB

0.00 to 1.00

 Input / Output

Maximum Level

dB

0 to 140

0 dB to 120 dB

0.00 to 1.00

 Output

Reset Maximum Level

0

1

false

true

0

1

 Input / Output

SPL Meter

The Meter Type in the Properties must be set to SPL to see the following control pins.

Pin Name

Value

String

Position

Pins Available
Infinite Maximum Hold

0

1

false

true

0

1

 Input / Output
Maximum Hold Time

1 to 100

1.00s to 100s

0.00 to 1.00

 Input / Output

Sound Pressure Level

dB

0 to 100

up to

40 to 140

0 dB to 100 dB

up to

40 dB to 140 dB

0.00 to 1.00

 Output
Time Weighting

0.100 to 10.0

100ms to 10.0s

0.00 to 1.00

 Input / Output

Leq Meter

The Meter Type in the Properties must be set to Leq to see the following control pins.

Pin Name

Value

String

Position

Pins Available
Leq (dBA)

0 to 100

up to

40 to 140

0 dBA to 100 dBA

up to

40 dBA to 140 dBA

0.00 to 1.00

 Output
Leq Time

0.100 to 3600

100ms to 3600s

0.00 to 1.00

 Input / Output
Level Updated 1

0

1

false

true

0

1

 Output
1. The Level is updated at the interval set by the Leq Time control. This output is available only on this Control Pin, to be used in scripts that post-process and/or log the measured level.

The measured Leq can be exposed via the Leq, Leq Time, and Level Updated control pins wired to a custom script that logs the values to one or more files.

Copy 
os = require "os"
io = require "io"

Controls.Inputs[3].EventHandler = function()
     time = string.format( "%.1f", Controls.Inputs[2].Value )
     level = string.format( "%.1f", Controls.Inputs[1].Value )
     filename = "media/Audio/" .. "A_weighted_Leq_" .. os.date( "%Y_%m_%d" ) .. ".csv"
     data = os.date( "%H:%M:%S" ) .. "," .. time .. "," .. level .. "\r\n"
     file = io.open( filename, "a+" )
     file:write( data )
     file:close()
end