SPL / L_eq Meter Component (BETA)

The SPL / L_eq 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.

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

Calibration Procedure

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.

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

Controls

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 following controls are common to both SPL and L_eq meter types.

Control	Function	Default/Range
Reference Level dB	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.	Default = 85 Range = 0 to 140
Calibrate	After setting the Reference Level, click this button to calibrate the meter. Refer to the Calibration Procedure for details.	N/A
Reset Max	Click this button to reset the maximum level.	N/A
Capture	Click this button to capture the current level reading.	N/A

SPL Meter Controls

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

Control	Function	Default/Range
Time Weighting (seconds)	This control determines the meter’s response time to changing levels. There are two standard weightings, Slow (1s) and Fast (125ms).	Default = 1.00 Range = 100ms to 10.0s
Sound Pressure Level dB	Displays the current level.	Default = N/A Range = 0 to 100 up to 40 to 140
Max Hold Time (seconds)	Sets the time interval to reset the maximum level.	Default = 10 Range = 1 to 100
Infinite Max Hold	When on, this button causes the Max Hold Time to be ignored. The maximum level is held until manually reset.	Default = Off Range = Off/On
Max SPL dB	Keeps track of the maximum SPL level over time.	Default = N/A Range = 0 to 120

L_eq Meter Controls

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

Control	Function	Default/Range
Equivalent Continuous Sound Level	This graph shows a time chart of the most recent levels.	Default = N/A Range = 0 to 100 up to 40 to 140
L_eq Time (Seconds)	Determines the meter’s time interval over which the level is integrated and averaged.	Default = 1.00 Range = 100ms to 3600s
Max L_eq dB	Tracks the maximum L_eq level over time. Max L_eq is on infinite hold, and can only be reset manually with the Reset Max button.	Default = N/A Range = 0 to 100 up to 40 to 140
L_eq dB	Displays the current level.	Default = N/A Range = 0 to 140

Control

Function

Default/Range

Equivalent Continuous Sound Level

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

Default = N/A

Range =

0 to 100

up to

40 to 140

L_eq Time

(Seconds)

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

Default = 1.00

Range =

100ms to 3600s

Max L_eq

Tracks the maximum L_eq level over time.

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

Default = N/A

Range =

0 to 100

up to

40 to 140

L_eq

Displays the current level.

Default = N/A

Range = 0 to 140

Properties

Property	Function	Choices
Meter Type	Exponentially averaging SPL meter or Integrating-averaging L_eq meter	SPL / L_eq
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.	Linear (flat) ANSI S1.42 A ANSI S1.42 C
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.	0 - 100 10 - 110 20 - 120 30 - 130 40 - 140

Property

Function

Choices

Meter Type

Exponentially averaging SPL meter

Integrating-averaging L_eq meter

SPL / L_eq

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.

Linear (flat)

ANSI S1.42 A

ANSI S1.42 C

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.

0 - 100

10 - 110

20 - 120

30 - 130

40 - 140

Control Pins

The following Control Pins are common to both SPL and L_eq 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

L_eq Meter

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

Pin Name	Value	String	Position	Pins Available
L_eq (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
L_eq 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 L_eq 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.

Logging L_eq Measurements

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

Script Example

(input 1 = Leq, input 2 = Leq Time, input 3 = Level Updated)
(The hidden Level Updated control toggles between 0 and 1 when a new Leq value is available which is every Leq Time period.)
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/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

© 2009 - 2016 QSC, LLC. All rights reserved. QSC and the QSC logo are trademarks of QSC, LLC in the U.S. Patent and Trademark office and other countries. All other trademarks are the property of their respective owners.

http://patents.qsc.com.

SPL / Leq Meter Component (BETA)

Calibration Procedure

Controls

SPL Meter Controls

Leq Meter Controls

Properties

Control Pins

SPL Meter

Leq Meter

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.

Logging Leq Measurements

Script Example

SPL / L_eq Meter Component (BETA)

L_eq Meter Controls

L_eq Meter

1. The Level is updated at the interval set by the L_eq 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.

Logging L_eq Measurements