How to Set Custom SPL Metrics

How to Set Custom SPL Metrics

The SPL Config Dialog

A new installation of Smaart Suite or Smaart SPL will include five default measurement type options: Leq 10 A-weighted/C-weighted/unweighted, Exposure N (named for NIOSH sound exposure guidelines), and Exposure O (named for OSHA sound exposure guidelines).

An in-depth guide to SPL weighting can be found here.

These can be deleted or changed via the Custom Metrics tab of the SPL Config dialog, accessible via the [Ctrl] + [Shift} + [E] shortcut or through the Config drop-down menu. If the input channel selected for a meter is uncalibrated, the only available option will be FS Peak.

A guide to SPL calibration can be found here.

Creating Custom SPL Metrics

On the Custom Metrics tab of the SPL Config dialog you can also create your own custom measurement types for sound level metering. These can include SPL and Leq for individual one-octave bands in addition to standard A and C broadband frequency weighting, as well as C-A (the difference between C- and A-weighted Leq). Leq integration periods can range from 1 second up to 1440 minutes (24 hours).

1. To add a new user-defined measurement type, click the plus (+) button below the table to add a new row, then click on its Type field to select the desired base measurement type. These include Leq, dB SPL Fast or Slow, Exposure (N or O) or Peak.

2. For Leq measurements, you can then click on the Time field and specify the integration period in minutes or seconds. The default unit for this field is minutes, but you can add an "s" to the entry to set the unit to seconds instead. For example, just entering "10" will set a 10 minute buffer, but entering "10s" will set a 10 second buffer. After setting an integration time, press the [Enter] key on your keyboard to set the change.

3. Frequency weighting for SPL, Leq, or Peak sound level measurements can be set from the Weight column. Options include standard A and C weighting curves as well as "None", otherwise known as Z-weighting. For Leq measurements, you can also select C-A, which shows the difference between C-and A-weighted broadband sound levels. You can also set up Leq measurements for individual Octave bands by selecting "Octave". This will enable the list box in the Frequency column, where you can select the center frequency of the octave band that you want to monitor.

To add an exposure measurement type, click the plus (+) button and select Exposure N or Exposure O from the Type list. Both exposure metrics are calculated the same way, with their individual permissible exposure levels for an eight hour work shift and the "exchange rate" that determines reduction in allowable exposure time as sound level increases, the NIOSH (Exposure N) recommendations being stricter in both respects. There are no additional options to select for exposure measurements. Exposure meters display a percentage of the permissible daily dosage for sound at measured levels.

Once you have custom metrics set, you can view them in real-time on the plot, as well. Once you click "Start Logging", the list of options for live metrics will update, adding any new metrics at the bottom of the list.

For this example, I added a custom metric of Leq 15 C-A. Upon starting logging, it appeared at the bottom of the list of options in the plot's drop down menu.

Deleting Metrics

To delete an existing measurement type, select it in the list by clicking on its number in the first column on the left, then click the minus (-) button below the table. When you click the "OK" button to exit the dialog window, all applicable selector menus and lists will be updated to reflect your changes.

If you delete one of the default metrics, you can restore it by either recreating it manually or resetting your copy of Smaart to its default configuration.